Patent Publication Number: US-2021173948-A1

Title: Data security using request-supplied keys

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/048,126, filed on Jul. 27, 2018, which is a continuation of U.S. patent application Ser. No. 15/090,315, filed on Apr. 4, 2016, issued as U.S. Pat. No. 10,037,428, entitled “DATA SECURITY USING REQUEST-SUPPLIED KEYS,” which is a continuation of U.S. patent application Ser. No. 14/037,292, filed on Sep. 25, 2013, issued as U.S. Pat. No. 9,311,500, entitled “DATA SECURITY USING REQUEST-SUPPLIED KEYS,” the content of which are incorporated by reference herein in their entirety. This application also incorporates by reference for all purposes the full disclosure of U.S. patent application Ser. No. 14/037,282, filed Sep. 25, 2013, issued as U.S. Pat. No. 9,237,019, entitled “RESOURCE LOCATORS WITH KEYS.” 
    
    
     BACKGROUND 
     The security of computing resources and associated data is of high importance in many contexts. As an example, organizations often utilize networks of computing devices to provide a robust set of services to their users. Networks often span multiple geographic boundaries and often connect with other networks. An organization, for example, may support its operations using both internal networks of computing resources and computing resources managed by others. Computers of the organization, for instance, may communicate with computers of other organizations to access and/or provide data while using services of another organization. In many instances, organizations configure and operate remote networks using hardware managed by other organizations, thereby reducing infrastructure costs and achieving other advantages. With such configurations of computing resources, ensuring that access to the resources and the data they hold is secure can be challenging, especially as the size and complexity of such configurations grow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments in accordance with the present disclosure will be described with reference to the drawings, in which: 
         FIG. 1  shows an illustrative example of an environment in which various embodiments can be implemented; 
         FIG. 2  shows an illustrative example of an environment in which various embodiments can be implemented; 
         FIG. 3  shows an illustrative example of a representation of a request in accordance with at least one embodiment; 
         FIG. 4  shows an illustrative example of a process for submitting a request in accordance with at least one embodiment; 
         FIG. 5  shows an illustrative example of a process for processing a request in accordance with at least one embodiment; 
         FIG. 6  shows an illustrative example of a representation of a request in accordance with at least one embodiment; 
         FIG. 7  shows an illustrative example of a process for processing a PUT request in accordance with at least one embodiment; 
         FIG. 8  shows an illustrative example of a process for submitting a GET request in accordance with at least one embodiment; 
         FIG. 9  shows illustrative examples of a representations of requests in accordance with various embodiments; 
         FIG. 10  shows an illustrative example of a process for submitting a request in accordance with at least one embodiment; 
         FIG. 11  shows an illustrative example of an environment in which various embodiments can be implemented; 
         FIG. 12  shows an illustrative example of a process for processing a request in accordance with at least one embodiment; 
         FIG. 13  shows an illustrative example of an environment in which various embodiments can be implemented; 
         FIG. 14  shows an illustrative example of a process for processing a request in accordance with at least one embodiment; and 
         FIG. 15  illustrates an environment in which various embodiments can be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, various embodiments will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described. 
     Techniques described and suggested herein relate to the submission and processing of requests where the requests include cryptographic keys. The requests may be generated by and submitted from customers of a service provider, such as a computing resource service provider. Processing the requests may include use of the keys included in the requests to perform one or more cryptographic operations such as encryption, decryption and generation of electronic (digital) signatures on data. In some embodiments, the techniques described and suggested herein are used to enable server-side encryption (and/or related techniques such as decryption) where the key to be used for encryption/decryption is controlled by the client (i.e. device of the customer or operating on behalf of the customer). 
     In various embodiments, use of keys provided in requests is performed so that, except for a limited time during which the keys are used, the service provider lacks access to the key. For example, the service provider may operate a data storage service. A customer may transmit data to the service provider for storage by the data storage service. A request to the service provider may include a key to be used to encrypt the data. The service provider may obtain the key from the request and use the key to encrypt the data so that the encrypted data may be persistently stored using the data storage service. When the key is no longer needed (e.g., when encryption of the data has completed), the service provider may perform one or more operations to lose access to the key, such as by destroying or allowing to be destroyed any in-memory copies of the key. Any copies of the data in plaintext form may similarly be destroyed or allowed to be destroyed. Once the key and plaintext data has been destroyed, the customer can be assured that the provider is unable to decrypt the data. Thus, even if a security breach or other event at the provider causes access to the data not authorized by the customer, the breach by itself does not enable access to the data in plaintext form. 
     Keys may be provided in requests in various ways in accordance with different embodiments. For example, in some embodiments, the request includes the key in plaintext form. The plaintext key may be a symmetric key to be used in a symmetric key algorithm. The plaintext key may also be a public key of a public-private key pair for an asymmetric key algorithm, where the service provider lacks access to the private key of the key pair and the private key is accessible to an entity to be able to decrypt using the private key (e.g., the customer). In some embodiments, requests include keys in encrypted (wrapped) form. For example, the key may be encrypted so as to be decryptable by the service provider or another entity at the direction of the service provider. The key used to encrypt the key in the request may be a secret shared with an entity able to decrypt the key (e.g., service provider) or a public key of a public-private key pair where the private key is to be used by an entity to decrypt the encrypted key for processing the request. 
     Upon receipt of a request with a key, the service provider may access the key from the request, decrypting or causing to be decrypted, if applicable, and then process the request. Other operations may be performed, such as by verifying an electronic signature of the request or checking whether fulfillment of the request is in compliance with any applicable policy. Other details of operations that may be performed are discussed in more detail below. 
       FIG. 1  shows an illustrative example of an environment  100  in which various embodiments can be implemented. In the environment  100  a customer  102  transmits a request  104  to a service provider  106 . The customer  102 , for example, may utilize services of the service provider  106 . The service provider may provide any type of service relating to data which may be utilized by customers. Example services include data storage services, database services, services that process data and others. To submit a request  104  to the service provider  106  the customer  102  may transmit the request with the aid of one or more devices of the customer, such personal or laptop computers, mobile devices, tablet computing devices, electronic book readers and/or others as described in more detail below in connection with  FIG. 15 . In addition, the request  104  may be submitted in accordance with one or more automated processes of the customer  102 . For example, request  104  may be transmitted as a result of a human operator of a device of the customer  102  having interacted with a browser or other application on a device of the customer  102 . The request  104  may be an electronic request transmitted over a network, such as the Internet or any other network or combination of networks discussed below. In some embodiments, for example, the request  104  is a web service request to a web service interface provided by the service provider  106 . Generally, the request  104  may be configured in accordance with various protocols by which requests may be electronically submitted. 
     As illustrated in  FIG. 1 , the request  104  includes data  108  and a cryptographic key  110 . The data may include various types of information and may be formatted various ways in accordance with various embodiments. For example, in some embodiments, the data is organized as a file, such as a media file. Data may also be formatted in other ways. The data may be, for instance, organized for inclusion in a database or otherwise. The cryptographic key  110 , as discussed in more detail below, may be a key used to encrypt the data  108  or otherwise to perform one or more cryptographic operations on data. It should be noted, as will be discussed in more detail below, that the request  104  may also include the cryptographic key  110  in various ways. For example, in some embodiments, the request  104  includes the cryptographic key  110  in plaintext form. In other embodiments, the request  104  includes the cryptographic key in encrypted form. For example, as discussed in more detail below, the cryptographic key  110  may be encrypted by another key such that the service provider  106  or another system associated therewith is able to decrypt the encrypted cryptographic key  110 . In this manner, upon submission of the request  104  from the customer  102  to the service provider  106 , the service provider  106  may use the cryptographic key  110  to encrypt the data  108  received in the request  104  thereby generating encrypted data  112 . 
     The encrypted data  112  may then be stored in a data storage system  114 . The data storage system  114  while illustrated as separate from the service provider  106  may be a subsystem of the service provider  106 . For example, the request  104  may be submitted to a web server of the service provider  106  where the web server is configured to allow access to the data storage system  114 . Generally, the data storage system  114  may be operated as a service to customers such that customers can use resources of the service provider  106  for the purpose of storing data. Other embodiments also include those in which the data storage system  114  is separate from the service provider  106 . The data storage system  114  may, for example, be operated by an entity that is a third party to the service provider  106  and the customer  102 , or in some embodiments the data storage system  114  may be a subsystem of the customer  102 ; that is, a subsystem of a system of the customer  102 . It should be noted that terms such as “customer” and “service” provider can have multiple meanings and such meanings are clear from context. For example, the term “customer” may refer to an entity (e.g., a legal entity such as an organization or individual) or a system (e.g., computing device or network of computing devices) that support operations of a customer entity. Similarly, the term “service provider” may refer to a legal entity or a system supporting operations of a service provider entity. 
     As illustrated in  FIG. 1 , upon encryption of the data  108  to generate the encrypted data  112 , the service provider  106  may take one or more actions that cause the service provider  106  to lose access to the cryptographic key  110 . This is illustrated in  FIG. 1  as the service provider  106  passing the cryptographic key  110  to an icon labeled as trash. It should be noted that while passing the cryptographic key  110  into trash as illustrated in the figure for the purpose of illustration, various embodiments may take action to lose access to the cryptographic key  110  that do not necessarily involve the transmission of the cryptographic key  110 . For example, in some embodiments, upon receipt of the request  104  and use of the cryptographic key  110  the service provider  106  may perform one or more operations to destroy the cryptographic key  110 . Destruction of the cryptographic key  110  may be performed in various ways in accordance with various embodiments. For example, in some embodiments, the cryptographic key  110  and request  104  are not persistently stored by the service provider  106  but are maintained in volatile memory of a device of a service provider  106 . 
     Destruction of the cryptographic key  110  may be performed by allowing one or more memory locations that store the cryptographic key  110  to be overwritten with other data, such as data received as part of subsequent requests. Other operations may also be performed. For example, if the cryptographic key  110  is stored in volatile or nonvolatile memory, the cryptographic key  110  may be destroyed by overwriting (e.g., via one or more write operations intended to destroy the cryptographic key) one or more memory locations used to store the cryptographic key  110  with other data such as random data or nonrandom data such as a string of zeros. Generally, any operations that will cause the service provider  106  to lose access to the cryptographic key  110  may be used. In this manner, the customer  102  is able to submit requests to the service provider  106  with cryptographic keys that the customer  102  desires to be used to encrypt data  108 . Further, because the service provider  106  is, in various embodiments, configured to lose access to the cryptographic key  110  after use of the cryptographic key  110 , the customer  102  can be assured that the service provider, upon processing the request  104 , is unable to access the data  108  by decrypting the decrypted data  112 . In other words, the security of the data  112  is ultimately controlled by the customer  102  with the service provider  106  having access to the data for a limited time. 
     It should be noted that while various processes resulting in encrypted data (and corresponding decrypting data) are used throughout for the purpose of illustration, the various processes may vary in accordance with other embodiments. For example, example processes for encryption illustrated herein show encryption using a key supplied by a customer of a service provider and where encryption is performed such that after an amount of time the service provider loses access to the key that was used. However, more complex schemes may also be used where more than one key is used to control access to data. For example, referring to  FIG. 1 , in some embodiments, data may be encrypted using both a key supplied by the customer in a request as well as a key held by or otherwise accessible to the service provider. In this manner, coordinated action between the customer  102  and the service provider  106  is required for access to the data  108  by way of having an ability to decrypt the encrypted data. In some embodiments, for example, the data  108  may be encrypted with one key and then again encrypted with another key. In other examples, the cryptographic key  110  may be combined with another key to generate yet another key used to encrypt the data  108 . Such variations may also be extended to multiple parties in addition to the customer  102  and the service provider  106  so that generally coordinated action by a plurality of entities is required for legitimate access to data that has been encrypted, that is to the data in plaintext form. Other variations are also considered as being within the scope of the present disclosure. 
     In addition, while various embodiments described herein illustrate requests that have certain types of data, requests may include other types of data. For example, requests my include data for various parameters of the request which may be used by a service provider to determine if, and/or how to, fulfill a request. Generally, requests as discussed herein are simplified for the purpose of illustration. The requests may, for instance, include various contextual data such as an identity of a requestor, a network address from which the request originates, an identity of an entity that generated some or all of the request and/or other types of data. 
     Further, it should also be noted, that while  FIG. 1  shows the request  104  having data  108  to be encrypted, requests within the scope of the present disclosure do not necessarily have data to be encrypted. For example, in some embodiments the requests may have a reference to data (e.g., an identifier of a data object, which may be in the form of a URL) that is not necessarily included in the request. Processing such a request may include using the reference to obtain the data. As another example, some requests may lack data because the requests include retrieval of data as one or more requested operations. A request to retrieve data may include a cryptographic key, but the data may be stored in another location. Processing the request may include accessing encrypted data to decrypt using the cryptographic key provided in the request. Other variations are also considered as being within the scope of the present disclosure. 
       FIG. 2  shows an illustrative example of an environment of a service provider  200  in accordance with various embodiments. As illustrated in  FIG. 2 , the service provider  200  includes a customer interface  202 . The customer interface may be a subsystem of the service provider  200  which allows for the submission of requests from customers to be processed by the service provider  200  such as described above in connection with  FIG. 1 . The customer interface may accordingly include appropriate computing devices for providing the ability for customers to submit requests to the service provider  200 . This customer interface, for example, may include one or more web servers configured to receive requests over the internet or another network. While not illustrated as such, other infrastructure may also be included in the customer interface  202 , such as appropriate networking equipment that enable the customer interface  202  to operate suitably for the customer of the service provider  200 . 
     When a request is received through the customer interface  202 , the request may be received with appropriate authenticating information. For example, as illustrated in  FIG. 2 , a request  204  may be received with a signature  206  of the request. The signature may be generated in accordance with various embodiments. For example, a customer that submitted the request  204  may generate the signature  206  using secret information shared between the customer and the service provider  200 . As another example, a customer may have used an asymmetric digital signature scheme to sign the request  204  using a private key of a private/public key pair. Generally, any type of information which is used to authenticate the request  204  may be used and, in some embodiments, requests may be submitted without such information. Further, in some embodiments, the electronic signature of a request is generated using a cryptographic key that is different than a cryptographic key supplied in the request, although in some embodiments, the electronic signature is generated using the same key that is supplied in the request. 
     As illustrated in  FIG. 2 , however, when a request  204  is received through the customer interface  202 , the request  204  is provided (e.g., over an internal network of the service provider  200 ) with the signature  206  to an authentication system  208  of the service provider  200 . Alternatively, a portion of the request sufficient for generating the electronic signature  206  may be provided instead of the whole request. The authentication system  208  may be a subsystem of the service provider  200  configured to authenticate requests such as by verifying electronic signatures provided with requests. Upon verifying the signature  206  of the request  204  the authentication system  208  may provide a response to the customer interface  202  that indicates whether the signature  206  is valid. A device of the customer interface  202  may use the information provided by the authentication system  208  in order to determine how to process the request  204 . For example, if the authentication system  208  indicates that the signature  206  is invalid, the customer interface  202  may deny the request. Similarly, if the information from authentication system  208  indicates that the signature  206  of the request  204  is valid, the customer interface  202  may cause the request  204  to be processed. 
     While not illustrated in the figure, the authentication system  208  or another system operating within or on behalf of the service provider  200  may operate to perform other operations in connection with determining how to process requests. For example, the authentication system  208  or another system operating in cooperation therewith may be used to check one or more policies which may be determinative of whether the request can be fulfilled. Policy determinations may be made based at least in part on various factors such as an identity of the requestor that submitted the request, a time of day, a logical identifier for a location in which data is stored or is to be stored and other contextual information. Policy may be managed through the customer interface  202  or another interface through appropriately-configured application programming interface (API) calls. 
     Returning to the embodiment illustrated in  FIG. 2 , if the authentication system  208  determines that the signature  206  is valid, the customer interface  202  may determine to process the request. Processing the request may involve the transfer of encrypted data  210  between the customer interface  202  and request processing infrastructure  212 . The request processing infrastructure  212  may comprise one or more devices that collectively operate to provide a service of the service provider  200 . For example, as illustrated in  FIG. 2 , the request processing infrastructure may comprise a plurality of data storage system  214  used to store data on behalf of customer of the service provider  200 . Other infrastructure including networking infrastructure while not illustrated may also be included. The passage of data, e.g., over a network between the customer interface  202  and the request processing infrastructure  212  may occur in various ways in accordance with various embodiments in accordance with the various types of requests that may be submitted through the customer interface  202 . For example, if the request  204  is a request to store data, a customer interface may utilize a key provided in the request  204  to encrypt the data and transmit the encrypted data  210  to the request processing infrastructure  212  for storage in one or more of the data storage systems  214 . 
     Similarly, if the request  204  is a request to retrieve data, a customer interface  202  may transmit a communication to the request processing infrastructure  212  that allows data from one or more of the data storage systems  214  to be provided to the customer interface  202 . The customer interface  202  may then use a key provided in the request  204  to decrypt the encrypted data  210  and provide the decrypted data to the customer that submitted the request  204 . It should be noted that the environment of the service provider  200  illustrated in  FIG. 2  is simplified for the purpose of illustration and that numerous other devices and subsystems such as accounting systems that keep track of usage of the service provider  200  by customers may also be included. Further, a service provider  200  may include facilities located in different geographical locations for the purpose of redundancy and/or availability. 
       FIG. 3  shows an illustrative example of a request  300  in accordance with various embodiments, where the request may be a request such as described above in connection with  FIGS. 1-2 . As illustrated in the example shown in  FIG. 3 , the request  300  includes a symmetric key which may be a cryptographic key used for both encryption and decryption of data. In an embodiment, the symmetric key  302  of the request  300  is provided in the request  300  in plaintext form. It should be noted that while the symmetric key is provided in the request  300  in plaintext form in some embodiments, the transfer of a request from a customer to a service provider or generally between entities may involve various protocols to ensure security of any data in the request  300 . For example, transmission of the request  300  may involve transport layer security (TLS) and/or another protocol such that the symmetric key  302  is encrypted during transmission from one entity to the other. Further, while  FIG. 3  shows a request  300  having a symmetric key  302  the request  300  may include other data which is not illustrated in the figure. Such data as discussed above may include various request parameters, authentication information, data to be encrypted, and/or other information. 
     In addition, while  FIG. 3  shows a request with a key, as with all requests described and illustrated herein, various other data may be provided within the request, such as data to be operated on and/or various metadata including contextual information about the request and authentication information usable to verify authenticity of the request. Various request parameters may also be included in the request. For instance, a request parameter may specify that server side encryption is supposed to be used to encrypt data using a key provided with the request. If such a parameter is absent and/or indicates that server side encryption is not to be used, the request may be processed without encryption being performed regardless of whether a key is included in the request. Further, for requests submitted with electronic signatures, a parameter may specify which part of the request was used to generate an electronic signature. Such a parameter can indicate which part of a request should be used for checking an electronic signature, thereby enabling requests to be modified after their generation, such as by adding data to be operated on during fulfillment of the request. Generally, requests are simplified in the present disclosure for the purpose of illustration. 
       FIG. 4  shows an illustrative example of a process  400  which may be used to transmit and receive a response to a request in accordance with various embodiments. The process  400  may be performed by any suitable system such as a device of a customer such as described above and below in connection with  FIG. 15 . In an embodiment, the process  400  includes obtaining  402  a cryptographic key. The cryptographic key may be obtained  402  in various ways in accordance with various embodiments. For example, in some embodiments the cryptographic key is obtained  402  by generating the cryptographic key. The cryptographic key may be generated for example using a random number generator or a key derivation function such as public key derivation function 2 (PPKDF2) or Bcrypt. The cryptographic key may be obtained  402  in other ways as well. For example, the cryptographic key may be accessed from a data storage device. As another example, the cryptographic key may be a password, passphrase, or other type of passcode accessed from memory and/or input by a user of a system performing the process  400 . Generally, any way of obtaining  402  a cryptographic key may be used. 
     With the cryptographic key having been obtained  402 , the process  400  may include generating  404  a request with the obtained cryptographic key; that is, generating a request that includes the obtained cryptographic key. The request may be generated by arranging data for the request in a manner suitable for transmission that is in a format processable by a system to which the request will be submitted. Once generated  404 , the generated request may be submitted  406 . Submission  406  of the generated request may be performed in any suitable manner such as by transmission to an Internet protocol (IP) address of a webserver configured to receive generated requests. Other operations may be performed, for example, in some embodiments the request is generated from a uniform resource locator (URL). Communication with the domain name service (DNS) may occur to obtain an IP address for the system to which the generated request is then submitted  406 . Generally any way of submitting the request may be performed. 
     Upon submission, a request may be processed by a system to which the generated request was submitted  406 . Accordingly, the process  400  may include receiving  408  a response to the request or the response may be an appropriately configured response in accordance with a protocol by which the request was submitted. It should be noted that not all embodiments require receipt of a response to the request. For example, some protocols may allow for the submission of requests without acknowledgement that the request has been received and/or fulfilled. As an illustrative example, the request may be to store data. In some embodiments, upon submission it may be assumed that the request has been processed or likely had been processed where acknowledgement of processing of the request may not be required. 
       FIG. 5  shows an illustrative example of a process  500  for processing a request where the request may be received such as described above and may have been submitted in accordance with a process such as the process  400  such as described above. The process  500  may be performed by any suitable system such as by a device (e.g., server) operating to provide a customer interface such as described above. In an embodiment, the process  500  includes receiving  502  a request with a cryptographic key. The request may be received  502  in various ways in accordance with various embodiments. For example as noted above, the request may be submitted over a network in accordance with a communication protocol and the request may therefore be received in accordance with such a protocol. Generally the request may be received  502  in any suitable way. 
     Upon receipt of the request, the process  500  may include determining  504  whether to fulfill the request. The determination  504  whether to fulfill the request may be made in various ways in accordance with various embodiments. For example as noted above, in some instances the request may be received with an electronic signature of the request. Accordingly, a determination may be made by determining whether the signature is valid. Determination of whether the signature is valid may be performed in various ways. For example, the system performing the process  500  may verify the signature itself or may transmit the signature and request (or generally data signed to generate the signature) to another system operable to verify the electronic signature. Further as noted above, determining  504  whether to fulfill the request may include performing a determination whether one or more policies would preclude fulfillment of the request. Generally any way by which a determination of whether to fulfill the request may be performed. 
     In addition, while  FIG. 5  and other processes illustrated herein show determinations whether to fulfill the request, in various embodiments, systems may fulfill all appropriately configured requests without the need to have a valid electronic signature and/or compliance with policy. Returning to the embodiment illustrated in  FIG. 5 , if it is determined  504  not to fill the request such as if a signature is invalid and/or policy precludes fulfillment of the request, the process  500  may include denying  506  the request. Denying  506  the request may be performed in various ways in accordance with various embodiments. For example, a response to the request may be provided that indicates that the request is denied and/or that provides information why the request was denied. As another example, denying the request may simply be performed by not taking any action. That is by not providing a response to the request and simply not fulfilling the request. Generally any way in which the request may not be fulfilled may be considered as denying the request. 
     If it is determined, however, to fulfill the request, the process  500  may include extracting  508  a cryptographic key from the request. The extracted cryptographic key may then be used  510  to perform one or more requested cryptographic operations; that is to perform one or more cryptographic operations involved in fulfillment of the request. The one or more cryptographic operations may vary in accordance with various embodiments and in accordance with the type of request that was received. In some embodiments for example, the one or more cryptographic operations include encryption of data included with the request and/or encryption of other data. As another example, the one or more cryptographic operations may include decryption of data referenced by and/or provided in the request. Generally any type of cryptographic operations such as key derivation and/or electronic signature generation and/or verification may be performed as part of the one or more cryptographic operations. Further, while various illustrative embodiments described herein show a single cryptographic operation such as encryption, multiple types of cryptographic operations may be performed while fulfilling a single request. As an example, one or more keys provided in a request may be used to encrypt data and generate an electronic signature of the data and/or encrypted data where the electronic signature can be used for later validation that the data has been changed. Other variations are also considered as being within the scope of the present disclosure. 
     Upon performance of the one or more cryptographic operations, the process  500  may include providing  512  a response to the request. The response may vary in accordance with the various embodiments and in accordance with the type of request that was made. For example, if the request was to retrieve data, the response may include data that was retrieved and decrypted. If the request was to store data, the response may be an acknowledgement that the data has been stored. A check sum or other validation information may be provided with the response. At some point subsequent to performance of the one or more cryptographic operations involved in fulfillment of the request, the process  500  may include losing  514  access to the extracted cryptographic key where access may be lost in various ways such as described above. 
       FIG. 6  is an illustrative example of a request  600  in accordance with various embodiments. As illustrated in  FIG. 6 , unlike the request described above in connection with  FIG. 3 , the request  600  includes a customer public key  602  which may be a public key of a public/private key pair where the private key is held by or on behalf of the customer. As with other requests described herein, the request  600  may include other data such as described above. The request  600  may be submitted such as described above in connection with  FIG. 4 . 
       FIG. 7  shows an illustrative example of a process  700  which may be used to process a request that includes a customer public key such as described above in connection  FIG. 6 . The process  700  may be performed by any suitable system, such as a system providing a customer interface such as described above. As illustrated in  FIG. 7 , the process  700  includes receiving  702  a PUT request with a customer public key; that is a PUT request (i.e., a request to store data) that has, as part of the request, a customer public key. The request may be received  702  such as described above and generally in any suitable manner. Upon receipt  702  of the PUT request with the customer public key the process  700  may include determining  704  whether to fulfill the request where the determination whether to fulfill the request may be made such as described above. If it is determined  704  that the request should not be fulfilled, the process  700  may include denying  706  the request such as described above. If, however, it is determined  704  that the request should be fulfilled, the process  700  may include extracting  708  a customer public key from the request for use. In an embodiment, the process  700  includes obtaining  710  an encryption key where the encryption key may be a symmetric key such as described above. The encryption may be obtained  710  in any suitable manner such as described above. For example, the encryption key may be accessed from data storage or generated. The obtained  710  encryption key may be used  712  to encrypt data that was provided in the request or otherwise requested by the request to be encrypted. The customer public key may be used  714  to encrypt (wrap) the encryption key. In this manner, the encrypted encryption key is decryptable using a private key corresponding to a customer public key. Thus, if a provider performing the process  700  does not have access to the encrypted encryption key, the provider cannot decrypt the encrypted encryption key. 
     The process  700  may also include storing  716  the encrypted data. The encrypted data may be, for example, transmitted to a data storage system for persistent storage thereof. A response to the request may be provided  718  where the response may include the encrypted encryption key. A system performing the process  700  may lose  720  access to the encryption key such as described above. In this manner, once a system performing the process  700  loses  720  access to the encryption key, the system no longer has the ability to decrypt the encrypted data and generally use of a private key corresponding to the customer public key is necessary to legitimately (i.e., without guessing the key or otherwise obtaining access to the data in an unauthorized manner) decrypt the encrypted data by first decrypting the encryption key in order to decrypt the decrypted data. 
     It should be noted, as with all processes described herein, variations are considered as being within the scope of the present disclosure. As an example,  FIG. 7  shows a process for processing a PUT request where the request includes a customer public key. Such request can be processed in different ways in accordance with various embodiments. In some embodiments for example, although use of a symmetric encryption key is generally computationally more efficient, a customer public key may be used to encrypt the data that was received in the request instead of using an encryption key that is then wrapped by the public key. In this manner, the data is decryptable only by an entity having access to the private key corresponding to the customer public key, which in various embodiments may be only the customer that submitted the request. 
     As another example of a variation considered as being within the scope of the present disclosure, the encrypted encryption key may be stored with the encrypted data and may or may not be transmitted in a response to the request. In such an embodiment to decrypt the data, the encryption key may be accessed from storage provided to an entity able to decrypt the encryption key (e.g., customer having a private key usable to decrypt the encryption key) which may then provide the decrypted encryption key back to enable decryption of the data. For example, a customer request to retrieve data may cause a provider to transmit an initial response with notification (including the encrypted encryption key) that the encryption key needs decrypting. The customer may decrypt the encryption key and provide the decrypted encryption key back to the provider to enable the provider to decrypt the encrypted data and provide the decrypted data to the customer. Other variations, including variations where ciphertext is provided to the customer from the provider along with an encrypted key usable to decrypt the ciphertext, are also considered as being within the scope of the present disclosure. For embodiments where, for example, server side encryption is used to PUT requests but client side encryption is used to obtain access to stored data, a provider may provide instructions for properly processing data (e.g., by properly canonicalizing data for decryption) or may provide executable instructions in the form of a client library to ensure that decryption is performed correctly (i.e., to ensure that decryption is performed in a manner that will succeed in decrypting the data). 
       FIG. 8  shows an illustrative example of a process  800  for obtaining data that has been stored in encrypted form by another system such as by a provider such as described above. The process  800  may be performed by any suitable system, such as by a device of a customer of a provider such as described above. In an embodiment, the process  800  includes obtaining  802  an encrypted encryption key. For example, the encrypted encryption key may have been received pursuant to performance of the process  700  described above or a variation thereof. Obtaining the encrypted encryption key may include receiving the encrypted encryption key or accessing the encrypted encryption key from persistent data storage. Generally the encrypted encryption key may be obtained  802  in any suitable manner. 
     A private key corresponding to a public key used to encrypt the encryption key may be used  804  to decrypt the encrypted encryption key. Once the decrypted encryption key has been obtained, the process  800  may include generating  806  a GET request with the decrypted encryption key and submitting (e.g., transmitting)  808  the generated GET request, such as described above. A system that receives the GET request may process the request by using the encryption key in the request to decrypt data that was encrypted by the encryption key. A response may then be received  810  where the response may include appropriate information such as data that has been decrypted using the decrypted encryption key that was provided in the GET request. 
     As with all processes described herein, variations of the process  800  are considered to be within the scope of the present disclosure. For example, the encrypted encryption key may be obtained by accessing the encrypted encryption key from remote storage when the encrypted encryption key is stored with the data that is encrypted under the encrypted encryption key. As another example, in some embodiments the process  800  may include submitting a GET request that is fulfilled by providing data encrypted under the encrypted encryption key. A system performing the process  800  may obtain the encrypted data and use the decrypted encryption key to decrypt the encrypted data. In other words, the process  800  may be modified so that data is decrypted client-side even if the data was encrypted server-side. 
       FIG. 9  shows an illustrative example of various requests that may include cryptographic keys that have been wrapped (i.e., encrypted) in various forms in accordance with various embodiments. For example,  FIG. 9  shows an illustrative example of a request  902  having a symmetric key  904  encrypted under a secret  906  shared with a provider where the secret shared with the provider may be another symmetric key shared between the customer and the provider. As another example,  FIG. 9  shows an example of a request  908  that includes a symmetric key  910  encrypted under a provider public key  912  which may be a public key corresponding to a public private key pair of which the provider has access to a corresponding private key. Another request  914  includes a symmetric key  916  encrypted under a secret  918  shared with a third party. That is an entity that is a third party to both a customer and a provider. As yet another example,  FIG. 9  shows a request  920  having a symmetric key  922  encrypted under a public key  924  of a third party where the third party may be a third party to a customer and provider. As noted, the requests illustrated in  FIG. 9  may also include additional information. 
       FIG. 10  shows an illustrative example of a process  1000  which may be used to submit a request in accordance with various embodiments. The process  1000  may be performed by any suitable system such as by a system of a customer of a provider such as described above. In an embodiment, the process  1000  includes obtaining  1002  a cryptographic key where the cryptographic key may be obtained  1002  such as described above. The obtained cryptographic key may be used to generate  1004  a wrapped cryptographic key that is the obtained cryptographic key encrypted under another key. Examples of wrapped cryptographic keys are described above in connection with  FIG. 9 . The process  1000  may include generating  1006  a request with the wrapped cryptographic key. That is the request may be generated to include the wrapped cryptographic key. The generated request may then be submitted  1008  such as described above. In various embodiments, the process  1000  may also include receiving  1010  a response to the request that was submitted  1008 . 
     As noted above, numerous embodiments are considered as being within in the scope of the present disclosure. In some embodiments, a customer and service provider are able to interact to achieve data security without use of a third party system to unwrap a key needed for cryptographic operations.  FIG. 11  accordingly shows an illustrative example of an environment  1100  in which various embodiments can be practiced. As with  FIG. 1 , as illustrated in  FIG. 11 , the environment  1100  includes a customer  1102  that submits a request  1104  to a service provider  1106 . In this example, the request  1104  includes an encryption key  1108  which, as indicated by the brackets surrounding the encryption key, is wrapped by another key. The service provider  1106  has access to a key  1110  usable to unwrap the encryption key thereby enabling the service provider  1106  to perform cryptographic operations using encryption key  1108 . 
       FIG. 12  shows an illustrative example of a process  1200  which may be used to process a request that includes a wrapped cryptographic key. The process  1200  may be performed by any suitable system such as by a webserver of a service provider  1106  described above in connection with  FIG. 11 . In an embodiment the process  1200  includes receiving  1202  a request that has a wrapped cryptographic key. A determination may be made  1204  whether to fulfill the request. If determined  1204  to not fulfill the request, the process  1200  may include denying  1206  the request such as described above. If, however, it is determined  1204  that the request should be fulfilled, the process  1200  may include extracting  1208  the wrapped cryptographic key from the request. 
     A key usable to unwrap the cryptographic key may be obtained  1210 . Obtaining the key usable to unwrap the cryptographic key may be performed in various ways in accordance with various embodiments. For example, the key usable to unwrap the wrapped cryptographic key may be stored by a system that performs the process  1200 . An identifier of the key usable to unwrap the wrapped cryptographic key may be used to locate the key usable to unwrap the wrapped cryptographic key from other keys which may be stored by the system. The identifier may be provided in the request that was received  1202  or may be otherwise determined such as by an association with an entity that submitted the request. Once the key usable to unwrap the wrapped cryptographic key has been obtained  1210 , the process  1200  may include using  1212  the obtained key to unwrap the wrapped cryptographic key. In this manner, an unwrapped cryptographic key is obtained. The unwrapped cryptographic key may be used  1214  to perform one or more cryptographic operations involved in fulfillment of the request that was received  1202 . A response to the request may be provided  1216  such as described above and access to the unwrapped cryptographic key may be lost  1218 . 
     In some embodiments, as noted, involvement of a third party is part of maintaining data security.  FIG. 13  accordingly shows an illustrative example of an environment  1300  with various embodiments can be practiced. The environment  1300  as illustrated includes a customer  1302  that submits a request  1304  to a service provider  1306  such as described above. Also as described above, the request  1304  may include an encryption key  1308  that is wrapped by another key such as described above in connection with  FIG. 9 . However, in the example of  FIG. 13 , a subsystem of the service provider  1306  that receives the request (or, in some embodiments, all subsystems of the service provider) may not have access to a key usable to unwrap the encryption key  1308 . Accordingly, the environment  1300  includes a key management system  1310  which has access to a key  1312  usable to unwrap the wrapped encryption key  1308 . The key management system  1310  may be any system operable to manage cryptographic keys on behalf of one or more customers of the service provider  1306 . 
     The key management system  1310  may be implemented in various ways in accordance with various embodiments. In some embodiments, the key management system is a subsystem of the service provider  1306  which may be implemented by, for instance, a hardware security module (HSM) hosted by the service provider  1306  or another type of security module that securely stores cryptographic keys. In some embodiments, the key management system  1310  is implemented as another service of the service provider  1306  which may be one of several services provided by the service provider  1306  and accessible to customer  1302  over a network such as described below. In some embodiments, the key management system is a system such as described above, however, implemented by a third party to the service provider  1306  and customer  1302 . In such embodiments, neither the customer  1302  nor the service provider  1306  has access to the key usable to unwrap the encryption key  1308  unless the key  1312  usable to unwrap the encryption key is shared with one or more of the customer  1302  or service provider  1306 . Other variations are also considered as being within the scope of the present disclosure. For example, the key management system  1310  may be implemented as part of the customer  1302  in some embodiments. Generally, the key management system  1310  is a system with which the service provider  1306  must communicate in order to unwrap or generally cause to have unwrapped the encryption key  1308  using the key  1312  usable to unwrap the encryption key. Communication between the service provider  1306  and the key management system  1310  may occur over one or more networks and in accordance with one or more appropriate network protocols. The network may be, for example, the Internet or any suitable network such as described below. 
       FIG. 14  shows an illustrative example of a process  1400  which may be performed to process a request that includes a wrapped encryption key such as described above in connection with  FIG. 13 . In an embodiment, the process  1400  includes receiving  1402  a request with the wrapped cryptographic key such as described above. As discussed above in connection with other processes, a determination may be made  1404  whether to fulfill the request, and if determined  1404  that the request should not be fulfilled the process  1400  may include denying  1406  the request. If, however, it is determined  1404  that the request should be fulfilled, the process  1400  may include extracting the wrapped cryptographic key from the request  1408 . The wrapped cryptographic key may be transmitted  1410  to an unwrapping system which may be a key management system such as described above as in connection with  FIG. 13  and generally which may be a system with access to a key usable to unwrap the wrapped cryptographic key. 
     The wrapped cryptographic key may be transmitted in the form of a request to the unwrapping system which is appropriately configured for fulfillment by the unwrapping system. For example, the request may be formatted in accordance with a format acceptable to the unwrapping system and the request may include information usable by the unwrapping system to determine whether to fulfill the request. Such information may include, for example, authentication information used to authenticate the request to the unwrapping system and/or the request that was received  1402  with the wrapped cryptographic key. Other information which may be used, for example, to determine whether fulfillment of the request to the unwrapping system complies with one or more policies may also be provided or the information may be contextual information such as described above. Additional information may include an identifier of a key usable to unwrap the wrapped cryptographic key. Assuming that the unwrapping system fulfills the request that was transmitted  1410 , the process  1400  may include receiving  1412  the unwrapped cryptographic key from the unwrapping system. The unwrapped cryptographic key may be used  1414  to perform one or more cryptographic operations involved in fulfillment of the request that was received  1402 . As response to the request may be provided  1416  such as described above and access to the unwrapped cryptographic key may be lost  1418 , such as described above. 
     As noted several times throughout the above disclosure, numerous variations are considered as being within the scope of the present disclosure. For example, as discussed, numerous variations utilize symmetric and/or asymmetric cryptographic primitives. Symmetric key algorithms may include various schemes for performing cryptographic operations on data including block ciphers, stream ciphers and digital signature schemes. Example symmetric key algorithms include, but are not limited to, the advanced encryption standard (AES), the data encryption standard (DES), triple DES (3DES), Serpent, Twofish, blowfish, CASTS, RC4 and the international data encryption algorithm (IDEA). Symmetric key algorithms may also include those used to generate output of one way functions and include, but are not limited to algorithms that utilize hash-based message authentication codes (HMACs), message authentication codes (MACs) in general, PBKDF2 and Bcrypt. Asymmetric key algorithms may also include various schemes for performing cryptographic operations on data. Example algorithms include, but are not limited to those that utilize the Diffie-Hellman key exchange protocol, the digital signature standard (DSS), the digital signature algorithm, the ElGamal algorithm, various elliptic curve algorithms, password-authenticated key agreement techniques, the pallier cryptosystem, the RSA encryption algorithm (PKCS #1), the Cramer-Shoup cryptosystem, the YAK authenticated key agreement protocol, the NTRUEncrypt cryptosystem, the McEliece cryptosystem, and others. Elliptic curve algorithms include the elliptic curve Diffie-Hellman (ECDH) key agreement scheme, the Elliptic Curve Integrated Encryption Scheme (ECIES), the Elliptic Curve Digital Signature Algorithm (ECDSA), the ECMQV key agreement scheme and the ECQV implicit certificate scheme. Other algorithms and combinations of algorithms are also considered as being within the scope of the present disclosure. 
     In addition, as noted, various embodiments of the present disclosure relate to the use of cryptographic keys included in requests to perform various cryptographic operations. While the keys are discussed as being used to perform the operations, it should be noted that various embodiments of the present disclosure include those where keys are transformed in some way before being used. As an example, in cases where a key in a request is a passcode, the passcode may be transformed (e.g., with a key derivation function) before being used to perform additional cryptographic operations. Further, while the above disclosure discusses specific types of keys (e.g., encryption keys) such keys may similarly be transformed before use. Other variations include those where multiple keys are provided in requests and request parameters and/or formatting of the request indicate how the multiple keys should be used. 
     Other variations considered as being within the scope of the present disclosure include embodiments that utilize pre-signed uniform resource locators (URLs). Referring to environments such as illustrated in  FIG. 1  that include a customer of a service provider, a customer can pre-generate URLs that include an electronic signature of a portion of the URL and/or other information, such as a cryptographic key. The customer may provide the URL to another entity and the other entity can utilize the URL to submit requests to the service provider to cause the service provider to perform one or more operations under the authorization of the customer. The service provider can receive a request submitted with the URL, verify the electronic signature, and perform the one or more operations using a key provided in the URL. In this manner, various conveniences involving server-side encryption and decryption with customer control over keys and provider inability to access keys except when necessary are achieved. The use of pre-signed URLs and variations thereof are discussed in detail in concurrently filed U.S. patent application Ser. No. 14/037,282, entitled “Resource Locators With Keys,” which is incorporated by reference in its entirety. 
       FIG. 15  illustrates aspects of an example environment  1500  for implementing aspects in accordance with various embodiments. As will be appreciated, although a web-based environment is used for purposes of explanation, different environments may be used, as appropriate, to implement various embodiments. The environment includes an electronic client device  1502 , which can include any appropriate device operable to send and receive requests, messages or information over an appropriate network  1504  and convey information back to a user of the device. Examples of such client devices include personal computers, cell phones, handheld messaging devices, laptop computers, tablet computers, set-top boxes, personal data assistants, embedded computer systems, electronic book readers and the like. The network can include any appropriate network, including an intranet, the Internet, a cellular network, a local area network or any other such network or combination thereof. Components used for such a system can depend at least in part upon the type of network and/or environment selected. Protocols and components for communicating via such a network are well known and will not be discussed herein in detail. Communication over the network can be enabled by wired or wireless connections and combinations thereof. In this example, the network includes the Internet, as the environment includes a web server  1506  for receiving requests and serving content in response thereto, although for other networks an alternative device serving a similar purpose could be used as would be apparent to one of ordinary skill in the art. 
     The illustrative environment includes at least one application server  1508  and a data store  1510 . It should be understood that there can be several application servers, layers or other elements, processes or components, which may be chained or otherwise configured, which can interact to perform tasks such as obtaining data from an appropriate data store. Servers, as used herein, may be implemented in various ways, such as hardware devices or virtual computer systems. In some contexts, servers may refer to a programming module being executed on a computer system. As used herein the term “data store” refers to any device or combination of devices capable of storing, accessing and retrieving data, which may include any combination and number of data servers, databases, data storage devices and data storage media, in any standard, distributed or clustered environment. The application server can include any appropriate hardware and software for integrating with the data store as needed to execute aspects of one or more applications for the client device, handling some (even a majority) of the data access and business logic for an application. The application server may provide access control services in cooperation with the data store and is able to generate content such as text, graphics, audio and/or video to be transferred to the user, which may be served to the user by the web server in the form of HyperText Markup Language (“HTML”), Extensible Markup Language (“XML”) or another appropriate structured language in this example. The handling of all requests and responses, as well as the delivery of content between the client device  1502  and the application server  1508 , can be handled by the web server. It should be understood that the web and application servers are not required and are merely example components, as structured code discussed herein can be executed on any appropriate device or host machine as discussed elsewhere herein. Further, operations described herein as being performed by a single device may, unless otherwise clear from context, be performed collectively by multiple devices, which may form a distributed system. 
     The data store  1510  can include several separate data tables, databases or other data storage mechanisms and media for storing data relating to a particular aspect of the present disclosure. For example, the data store illustrated may include mechanisms for storing production data  1512  and user information  1516 , which can be used to serve content for the production side. The data store also is shown to include a mechanism for storing log data  1514 , which can be used for reporting, analysis or other such purposes. It should be understood that there can be many other aspects that may need to be stored in the data store, such as page image information and access rights information, which can be stored in any of the above listed mechanisms as appropriate or in additional mechanisms in the data store  1510 . The data store  1510  is operable, through logic associated therewith, to receive instructions from the application server  1508  and obtain, update or otherwise process data in response thereto. In one example, a user, through a device operated by the user, might submit a search request for a certain type of item. In this case, the data store might access the user information to verify the identity of the user and can access the catalog detail information to obtain information about items of that type. The information then can be returned to the user, such as in a results listing on a web page that the user is able to view via a browser on the user device  1502 . Information for a particular item of interest can be viewed in a dedicated page or window of the browser. It should be noted, however, that embodiments of the present disclosure are not necessarily limited to the context of web pages, but may be more generally applicable to processing requests in general, where the requests are not necessarily requests for content. 
     Each server typically will include an operating system that provides executable program instructions for the general administration and operation of that server and typically will include a computer-readable storage medium (e.g., a hard disk, random access memory, read only memory, etc.) storing instructions that, when executed by a processor of the server, allow the server to perform its intended functions. Suitable implementations for the operating system and general functionality of the servers are known or commercially available and are readily implemented by persons having ordinary skill in the art, particularly in light of the disclosure herein. 
     The environment in one embodiment is a distributed computing environment utilizing several computer systems and components that are interconnected via communication links, using one or more computer networks or direct connections. However, it will be appreciated by those of ordinary skill in the art that such a system could operate equally well in a system having fewer or a greater number of components than are illustrated in  FIG. 15 . Thus, the depiction of the system  1500  in  FIG. 15  should be taken as being illustrative in nature and not limiting to the scope of the disclosure. 
     The various embodiments further can be implemented in a wide variety of operating environments, which in some cases can include one or more user computers, computing devices or processing devices which can be used to operate any of a number of applications. User or client devices can include any of a number of general purpose personal computers, such as desktop, laptop or tablet computers running a standard operating system, as well as cellular, wireless and handheld devices running mobile software and capable of supporting a number of networking and messaging protocols. Such a system also can include a number of workstations running any of a variety of commercially-available operating systems and other known applications for purposes such as development and database management. These devices also can include other electronic devices, such as dummy terminals, thin-clients, gaming systems and other devices capable of communicating via a network. 
     Various embodiments of the present disclosure utilize at least one network that would be familiar to those skilled in the art for supporting communications using any of a variety of commercially-available protocols, such as Transmission Control Protocol/Internet Protocol (“TCP/IP”), protocols operating in various layers of the Open System Interconnection (“OSI”) model, File Transfer Protocol (“FTP”), Universal Plug and Play (“UpnP”), Network File System (“NFS”), Common Internet File System (“CIFS”) and AppleTalk. The network can be, for example, a local area network, a wide-area network, a virtual private network, the Internet, an intranet, an extranet, a public switched telephone network, an infrared network, a wireless network and any combination thereof. 
     In embodiments utilizing a web server, the web server can run any of a variety of server or mid-tier applications, including Hypertext Transfer Protocol (“HTTP”) servers, FTP servers, Common Gateway Interface (“CGP”) servers, data servers, Java servers and business application servers. The server(s) also may be capable of executing programs or scripts in response to requests from user devices, such as by executing one or more web applications that may be implemented as one or more scripts or programs written in any programming language, such as Java®, C, C # or C++, or any scripting language, such as Perl, Python or TCL, as well as combinations thereof. The server(s) may also include database servers, including without limitation those commercially available from Oracle®, Microsoft®, Sybase® and IBM®. 
     The environment can include a variety of data stores and other memory and storage media as discussed above. These can reside in a variety of locations, such as on a storage medium local to (and/or resident in) one or more of the computers or remote from any or all of the computers across the network. In a particular set of embodiments, the information may reside in a storage-area network (“SAN”) familiar to those skilled in the art. Similarly, any necessary files for performing the functions attributed to the computers, servers or other network devices may be stored locally and/or remotely, as appropriate. Where a system includes computerized devices, each such device can include hardware elements that may be electrically coupled via a bus, the elements including, for example, at least one central processing unit (“CPU” or “processor”), at least one input device (e.g., a mouse, keyboard, controller, touch screen or keypad) and at least one output device (e.g., a display device, printer or speaker). Such a system may also include one or more storage devices, such as disk drives, optical storage devices and solid-state storage devices such as random access memory (“RAM”) or read-only memory (“ROM”), as well as removable media devices, memory cards, flash cards, etc. 
     Such devices also can include a computer-readable storage media reader, a communications device (e.g., a modem, a network card (wireless or wired), an infrared communication device, etc.) and working memory as described above. The computer-readable storage media reader can be connected with, or configured to receive, a computer-readable storage medium, representing remote, local, fixed and/or removable storage devices as well as storage media for temporarily and/or more permanently containing, storing, transmitting and retrieving computer-readable information. The system and various devices also typically will include a number of software applications, modules, services or other elements located within at least one working memory device, including an operating system and application programs, such as a client application or web browser. It should be appreciated that alternate embodiments may have numerous variations from that described above. For example, customized hardware might also be used and/or particular elements might be implemented in hardware, software (including portable software, such as applets) or both. Further, connection to other computing devices such as network input/output devices may be employed. 
     Storage media and computer readable media for containing code, or portions of code, can include any appropriate media known or used in the art, including storage media and communication media, such as, but not limited to, volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage and/or transmission of information such as computer readable instructions, data structures, program modules or other data, including RAM, ROM, Electrically Erasable Programmable Read-Only Memory (“EEPROM”), flash memory or other memory technology, Compact Disc Read-Only Memory (“CD-ROM”), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other medium which can be used to store the desired information and which can be accessed by the system device. Based on the disclosure and teachings provided herein, a person of ordinary skill in the art will appreciate other ways and/or methods to implement the various embodiments. 
     The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims. 
     Other variations are within the spirit of the present disclosure. Thus, while the disclosed techniques are susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the disclosed embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected,” when unmodified and referring to physical connections, is to be construed as partly or wholly contained within, attached to or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein and each separate value is incorporated into the specification as if it were individually recited herein. The use of the term “set” (e.g., “a set of items”) or “subset” unless otherwise noted or contradicted by context, is to be construed as a nonempty collection comprising one or more members. Further, unless otherwise noted or contradicted by context, the term “subset” of a corresponding set does not necessarily denote a proper subset of the corresponding set, but the subset and the corresponding set may be equal. 
     Conjunctive language, such as phrases of the form “at least one of A, B, and C,” or “at least one of A, B and C,” unless specifically stated otherwise or otherwise clearly contradicted by context, is otherwise understood with the context as used in general to present that an item, term, etc., may be either A or B or C, or any nonempty subset of the set of A and B and C. For instance, in the illustrative example of a set having three members used in the above conjunctive phrase, “at least one of A, B, and C” and “at least one of A, B and C” refers to any of the following sets: {A}, {B}, {C}, {A, B}, {A, C}, {B, C}, {A, B, C}. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of A, at least one of B and at least one of C to each be present. 
     Operations of processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. Processes described herein (or variations and/or combinations thereof) may be performed under the control of one or more computer systems configured with executable instructions and may be implemented as code (e.g., executable instructions, one or more computer programs or one or more applications) executing collectively on one or more processors, by hardware or combinations thereof. The code may be stored on a computer-readable storage medium, for example, in the form of a computer program comprising a plurality of instructions executable by one or more processors. The computer-readable storage medium may be non-transitory. 
     The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this disclosure are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate and the inventors intend for embodiments of the present disclosure to be practiced otherwise than as specifically described herein. Accordingly, the scope of the present disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the scope of the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context. 
     All references, including publications, patent applications and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.