Patent Publication Number: US-11646871-B2

Title: System and method for multitenant key derivation

Description:
BACKGROUND 
     Many computer applications require cryptographic operations for multiple clients, users, or processes. For example, multiple clients may require separate keys for accessing applications hosted by servers or cloud-based systems through one or more networks. To enhance security in case of a breach, server/cloud side key management systems may be separated. For example, if an attacker breaches one key server, they may only gain a small number of the total keys, and may have to breach additional servers separately to gain more keys. 
     Due to their complexity, currently existing key management services require separate groups of servers per project and therefore introduce tremendous overall costs due to the additional hardware and overhead. These services also require large storage resources to store the numerous keys being managed and used for encryption and decryption purposes, and the storage of encrypted data. Moreover, these services also utilize complex exponential processing during key generation and derivation processing, meaning that they are also processor intensive. As can be appreciated, all of these results are undesirable. 
     Accordingly, there is a need and desire for a new and improved multitenant key derivation process that overcomes the shortcomings of today&#39;s key management services. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    shows an example system configured to perform multitenant key derivation according to an embodiment of the present disclosure. 
         FIG.  2    shows an example computing device according to an embodiment of the present disclosure. 
         FIG.  3    shows an example multitenant key derivation process according to an embodiment of the present disclosure. 
         FIG.  4    shows an example multitenant key derivation protocol according to an embodiment of the present disclosure. 
         FIG.  5    shows an example key rotation protocol according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS 
     Some embodiments described herein may enable multitenant key derivation and management using a unique protocol in which (remote) key derivation may be executed between the server that holds the root key and a client that holds the derivation data and obtains an encryption key. In one or more embodiments, the derivation data may be hashed and may include some information, potentially secret, associated with the data to be encrypted. The use of the hashed data and processing disclosed herein provides the advantage of simplifying the computations used throughout the process such as e.g., by removing complex derivation computations that utilize exponents and exponential processing. Instead, the principles disclosed herein are based on simplified multiplication operations rather than complex exponential processing, reducing the load on the processors when carrying out the disclosed protocol. In addition, the hashed data and processing disclosed herein allow for the use of very short headers when encrypted data (e.g., ciphertext) is stored. Thus, the principles disclosed herein require significantly less storage resources to store the keys being managed and used for encryption and decryption purposes. 
     Moreover, the disclosed protocol ensures that the server does not get access to or learn anything about the client&#39;s derived key, while the client does not get access to or learn anything about the server&#39;s root key. Significantly, the server cannot force the derived key to a value of its choice. These features allow the protocol to run simultaneous mutually distrustful key derivation processes on the same cluster of machines, thereby reducing the number of servers needed when keys for multiple projects are being derived and or managed. 
     In one or more embodiments, the protocol may be executed between a client computing device and one or more server computing devices in communication with the client computing device. In one or more embodiments, the protocol may have the following high level structure: (1) the client computing device may provide blinded and or hashed derivation data, while the one or more server computing devices (2) may provide an encrypted key, and (3) may compute a derived key based on the root key and the derivation data. In one or more embodiments, the derived key may be blinded when on the one or more server computing devices, meaning that the one or more server computing devices will not have access to the cleartext derived key, and can only be unblinded (revealed) by the client. 
     In one or more embodiments, the one or more server computing devices implement a remote crypto cluster (RCC), virtual key manager (VKM) and a project key server (PKS). In one or more embodiments, the protocol may have the following high level structure: (1) the client computing device may provide blinded and or hashed derivation data, (2) the VKM may provide an encrypted key, and (3) the RCC may compute a derived key based on the root key and the derivation data. In one or more embodiments, the derived key may be blinded when on the RCC, meaning that the RCC will not have access to the cleartext derived key, and can only be unblinded (revealed) by the client. 
       FIG.  1    shows an example system  100  configured to perform multitenant key derivation according to an embodiment of the present disclosure. In the illustrated example, the system  100  includes elements such as a remote crypto cluster (RCC)  120 , virtual key manager (VKM)  130 , project key server (PKS)  140 , and/or at least one client  150 . Each of these elements may include one or more physical computing devices (e.g., which may be configured as shown in  FIG.  2   ). In one or more embodiments, the RCC  120  may be merged into the VKM  130 . In some embodiments, the client  150  may be any device configured to provide access to remote applications. For example, the client  150  may be a smartphone, personal computer, tablet, laptop computer, or other device. It should be appreciated that the disclosed principles should not be limited to the illustrated example and that they can be applied to one or more server computing devices that are separate from a client computing device. 
     The elements may communicate with one another through at least one network  110 . Network  110  may be the Internet and/or other public or private networks or combinations thereof. For example, in some embodiments, at least the RCC  120 , VKM  130 , and PKS  140  may communicate with one another over secure channels (e.g., one or more TLS/SSL channels). In some embodiments, communication between at least some of the elements of the system  100  may be facilitated by one or more application programming interfaces (APIs). APIs of the system  100  may be proprietary and/or may be examples available to those of ordinary skill in the art such as Amazon® Web Services (AWS) APIs or the like. 
     Specific examples of the processing performed by the elements of the system  100  in combination with one another are given below with respect to the multitenant key derivation process  300  illustrated in  FIG.  3   , the multitenant key derivation protocol  400  illustrated in  FIG.  4   , and or the project key rotation protocol  310  illustrated in  FIG.  5   . 
     The RCC  120 , VKM  130 , PKS  140 , and client  150  are each depicted as single devices for ease of illustration, but those of ordinary skill in the art will appreciate that the RCC  120 , VKM  130 , PKS  140 , and/or client  150  may be embodied in different forms for different implementations. For example, the RCC  120  may be merged into the VKM  130  and they may reside on one or more computing devices. In other embodiments, the RCC  120 , VKM  130 , and/or PKS  140  may include a plurality of devices. In another example, a plurality of clients  150  may be connected to the network  110  and may use the key derivation services described herein. Furthermore, as noted above, the network  110  may be a single network or a combination of networks, which may or may not all use similar communication protocols and/or techniques. 
       FIG.  2    is a block diagram of an example computing device  200  that may implement various features and processes as described herein. For example, in some embodiments the computing device  200  may function as the RCC  120 , VKM  130 , PKS  140 , or client  150 , or a portion of any of these elements. The computing device  200  may be implemented on any electronic device that runs software applications derived from instructions, including without limitation personal computers, servers, smart phones, media players, electronic tablets, game consoles, email devices, etc. In some implementations, the computing device  200  may include one or more processors  202 , one or more input devices  204 , one or more display devices  206 , one or more network interfaces  208 , and one or more computer-readable mediums  210 . Each of these components may be coupled by a bus  212 . 
     The display device  206  may be any known display technology, including but not limited to display devices using Liquid Crystal Display (LCD) or Light Emitting Diode (LED) technology. The processor(s)  202  may use any known processor technology, including but not limited to graphics processors and multi-core processors. The input device  204  may be any known input device technology, including but not limited to a keyboard (including a virtual keyboard), mouse, track ball, and touch-sensitive pad or display. The bus  212  may be any known internal or external bus technology, including but not limited to ISA, EISA, PCI, PCI Express, USB, Serial ATA or FireWire. The computer-readable medium  210  may be any non-transitory medium that participates in providing instructions to the processor(s)  202  for execution, including without limitation, non-volatile storage media (e.g., optical disks, magnetic disks, flash drives, etc.), or volatile media (e.g., SDRAM, ROM, etc.). 
     The computer-readable medium  210  may include various instructions  614  for implementing an operating system (e.g., Mac OS®, Windows®, Linux). The operating system may be multi-user, multiprocessing, multitasking, multithreading, real-time, and the like. The operating system may perform basic tasks, including but not limited to: recognizing input from the input device  204 ; sending output to the display device  206 ; keeping track of files and directories on the computer-readable medium  210 ; controlling peripheral devices (e.g., disk drives, printers, etc.) which can be controlled directly or through an I/O controller; and managing traffic on the bus  212 . The network communications instructions  216  may establish and maintain network connections (e.g., software for implementing communication protocols, such as TCP/IP, HTTP, Ethernet, telephony, etc.). 
     The key derivation service instructions  218  may include instructions that perform the various multitenant key derivation functions as described herein. The key derivation service instructions  218  may vary depending on whether the computing device  200  is functioning as the RCC  120 , VKM  130 , PKS  140 , or client  150 . For example, the RCC  120  may include key derivation service instructions  218  for requesting data from other devices and using it to compute a blinded derived key. The client  150  may include key derivation service instructions  218  for generating public/private key pairs and using the private key to decrypt the blinded derived key. The VKM  130  and/or PKS  140  may include key derivation service instructions  218  for generating and/or transmitting data used throughout the process  300 , protocol  400  and or required by other devices. 
     The application(s)  220  may be an application that uses or implements the processes described herein and/or other processes. The processes may also be implemented in the operating system  214 . 
     The described features may be implemented in one or more computer programs that may be executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result. A computer program may be written in any form of programming language (e.g., Objective-C, Java), including compiled or interpreted languages, and it may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. 
     Suitable processors for the execution of a program of instructions may include, by way of example, both general and special purpose microprocessors, and the sole processor or one of multiple processors or cores, of any kind of computer. Generally, a processor may receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer may include a processor for executing instructions and one or more memories for storing instructions and data. Generally, a computer may also include, or be operatively coupled to communicate with, one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data may include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, ASICs (application-specific integrated circuits). 
     To provide for interaction with a user, the features may be implemented on a computer having a display device such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer. 
     The features may be implemented in a computer system that includes a back-end component, such as a data server, or that includes a middleware component, such as an application server or an Internet server, or that includes a front-end component, such as a client computer having a graphical user interface or an Internet browser, or any combination thereof. The components of the system may be connected by any form or medium of digital data communication such as a communication network. Examples of communication networks include, e.g., a telephone network, a LAN, a WAN, and the computers and networks forming the Internet. 
     The computer system may include clients and servers. A client and server may generally be remote from each other and may typically interact through a network. The relationship of client and server may arise by virtue of computer programs running on the respective computers and having a client-server relationship to each other. 
     One or more features or steps of the disclosed embodiments may be implemented using an API. An API may define one or more parameters that are passed between a calling application and other software code (e.g., an operating system, library routine, function) that provides a service, that provides data, or that performs an operation or a computation. 
     The API may be implemented as one or more calls in program code that send or receive one or more parameters through a parameter list or other structure based on a call convention defined in an API specification document. A parameter may be a constant, a key, a data structure, an object, an object class, a variable, a data type, a pointer, an array, a list, or another call. API calls and parameters may be implemented in any programming language. The programming language may define the vocabulary and calling convention that a programmer will employ to access functions supporting the API 
     In some implementations, an API call may report to an application the capabilities of a device running the application, such as input capability, output capability, processing capability, power capability, communications capability, etc. 
     The disclosed principles will be described as involving a project associated with n clients, that each use the key-derivation process disclosed herein to securely derive keys with at least the following properties: 1) the derived keys are pseudo-random; 2) every key can be derived by any client using appropriate derivation data; and 3) the derivation data is available to all clients associated with the project. Moreover, in one or more embodiments, any two clients may derive the same key given the same root key and same derivation data. 
     In accordance with the disclosed principles, the VKM  130 , RCC  120  and PKS  150  may participate in the multitenant key derivation process  300  ( FIG.  3   ) and multitenant key derivation protocol  400  ( FIG.  4   ) with the client  150 . In one or more embodiments, the VKM  130  may be in charge of managing the keys associated with the project, the RCC  120  may be in charge of participating in the key derivation process with the clients. In one or more embodiments, the RCC  120  is part of the VKM  130  and executed by it. In one or more embodiments, the PKS  140  may be in charge of managing the project key and client secret values required for the key-derivation process. In one or more embodiments, the communication channels are authenticated and private (e.g., authenticity and secrecy of the communications are obtained using SSL (Secure Sockets Layer), which is a secure protocol developed for sending information securely over the Internet). 
       FIG.  3    shows an example multitenant key derivation process  300  according to an embodiment of the present disclosure. The process  300  may consist of two phases: a setup phase  302  and a derivation phase  304 . In one or more embodiments, the process  300  may support a project key rotation protocol  310 . In one or more embodiments, the setup phase  302  may be used generate one or more setup parameters or other values needed for the derivation phase  304  and or the project-key rotation protocol  310 . The derivation phase  304  may consist of several subroutines that can be executed by the clients. In one or more embodiments, the project key rotation protocol  310  may be used to generate a fresh project key and (atomically) update the relevant database records. As such, the project key rotation protocol  310  may be characterized as a rekeying process. 
     Some portions of process  300  and other processes discussed herein are described as using specific equations. However, it will be clear to those of ordinary skill in the art that some portions of process  300  may be performed with modifications to the example equations and/or with different processing altogether. The following definitions may be useful for understanding the example equations presented herein:
         n is the number of clients.   For i∈[n], C i  is the i&#39;th client and b i  is the blinding value associated with client C i . A blinding value b i  is added to and or processed with other data to form blinded data, which can only be unblinded using the blinding value b i .      is the number of root keys in the project.   For j∈[ ], z j , v j , and t j  are respectively the j&#39;th RCC root key and additional variables used for derivation with z j . The length of z j , v j , and t j  is 2,048 bits.   DD is the derivation data supplied by the client.   (vsk, vpk) is the VKM&#39;s key pair for RSA encryption. These keys are generated once and vpk is known to all entities in the system.   (sk, vk) is the PKS&#39; key pair for an RSA signature scheme. These keys are generated once and vk is known to all entities in the system.   p is a 2,048 bit prime number generated once and is known to all entities in the system.   K is the project key (i.e., master key) that is generated in    p .   w is a project-wide client key that is shared among all clients and has a length of 2,048 bits.   pks-project-key-version is the latest project key version generated by the PKS.   vkm-project-key-version is the latest project key version received by VKM.   key-update-value is the ratio of the current project-key and previous project key.       

     All the definitions are presented as being within the scope of a “project,” which may be a partitioning of the system  100  into multiple key namespaces and multiple clients associated with the namespaces, where (through cryptographic systems and/or methods) a client  150  may be prevented from using keys of a project unless the client  150  is associated with that project. The system  100  may be configured so that there may be simultaneous multiple projects, e.g., on the same RCC  120  and/or VKM  130 , while preserving the guarantee that the client  150  may have access only to keys of projects with which the client  150  is associated. 
     In accordance with the disclosed principles, keys may be used to access projects, which may be any protected service or process. When a project is first created and/or registered with the system  100 , the system  100  may perform the setup phase  302 . In one or more embodiments, during the setup phase  302 , the VKM  130  and PKS  140  may locally generate and set values of certain parameters that are required for, and may be fixed during, the whole life-cycle of the project. In one or more embodiments, rotation of certain secret values may be permitted to boost the security of the protocol  300 . 
     In one or more embodiments, part of the setup phase  302  is performed by the VKM  130  in response to receiving a VKM setup message “message (VKM setup)” from a user U. In one or more embodiments, the user U is a system operator or other personnel responsible for setting up a project and or its key name space. During the setup phase  302 , the VKM  130  may set vkm-project-key-version (i.e., the latest project key version received by VKM) to 1 and key-update-value (i.e., the ratio of the current project-key and previous project key) to 1. The VKM  130  may store the values of these parameters for later use in a protected keys record. 
     A second part of the setup phase  302  is performed by the PKS  140  in response to receiving a PKS setup message “message (PKS setup)” from the user U. During the setup phase  302 , the PKS  140  will uniformly sample at random w←{0, 1} 2048  and K←   p . The PKS  140  may set pks-project-key-version (i.e., the latest project key version generated by the PKS) to 1. The PKS  140  may store the values of these parameters for later use. 
     The derivation phase  304  may consist of a key generation process  306  and a key derivation protocol  400 . The key generation process  306  may be performed by the VKM  130  in response to receiving a message “message (VKM KeyGen, key-name)” from client C i  asking the VKM to generate a key-name. During the key generation process  306 , the VKM  130  may uniformly sample values at random for the following parameters: {circumflex over (z)} p ←   p , v j ←{0, 1} 2048  and t j {0, 1} 2048 . In one or more embodiments, the VKM  130  may set {circumflex over (z)} J =z j ·K, and store the values of z j ·K, v j , t j , and key-name. This is a protected key generation process performed locally at the VKM  130 , which uniquely defines the value of the specific key (since the project key has been defined at this stage). 
     The key derivation protocol  400  can be performed locally on the client side or remotely involving the VKM  130  (and or RCC  120 ) as discussed below in more detail with respect to  FIG.  4   . In one or more embodiments, the key derivation protocol  400  will utilize keyed hash function (“HKDF”) computations performed by the VKM  130  and the client  150 . In one or more embodiments, the keyed hash function HKDF is computed on (key, value, output bit length) as described in more detail below. In accordance with the disclosed principles, the HKDF computations performed by the VKM  130  are used to prevent a dictionary attack on the derivation-data. 
     In the key rotation protocol  310 , a fresh project key may be generated by the PKS  140  and the VKM  130  will update the protected keys record with the appropriate values. In one or more embodiments, the key database may be updated via an atomic update operation. 
       FIG.  4    illustrates an example multitenant key derivation protocol  400  according to an embodiment of the present disclosure. The entire system  100  may work together to perform protocol  400  in a distributed manner. In accordance with the disclosed principles, the client computing  150  may provide blinded and or hashed derivation data, the VKM  130  may provide an encrypted key, and the RCC  120  may compute a derived key based on the root key and the derivation data. In one or more embodiments, the derived key may be blinded when on the RCC,  120  meaning that the RCC  120  will not have access to the cleartext derived key, and can only be unblinded (revealed) by the client  150 . This arrangement may yield a low-cost, multitenant system  100  with strong protection of stored and/or managed data. The protocol  400  is presented as deriving a single key for a single project or use, but it should be appreciated that the protocol  400  may be performed repeatedly to generate multiple keys in some embodiments, if desired. 
     At this point, because the setup phase  302  and key generation process  306  of the process  300  have already been performed, the VKM  130 , PKS  140  and client  150  may have the following information, states and or conditions. The VKM  130  may have a stored protected keys record comprising the z j ·K, v j , t j  and key-name parameters (“protected keys record (z j ·K, v j , t j  and key-name)” and the parameters key-update-value, and vkm-project-key-version. The PKS  140  may comprise the project key K, client-key w, and the pks-project-key-version parameter. The client  150  may comprise the derivation data DD and a message m to be encrypted. The client&#39;s  150  cache storage may include the client-key w, key identifier t j , client blinding value b i , ciphertext e i , and a signature σ i  on the ciphertext e i . In one or more embodiments, the ciphertext e i  is based on an encryption of the tuple b i ·K and pks-project-key-version (i.e., e i =ENC vpk (b j ·K|pks-project-key-version). In one or more embodiments, RSA encryption and signatures are used throughout the protocol  400 . In one or more embodiments, the RSA encryption and signatures use a bit length of 2048. 
     At step  402 , the client  150  determines if the key identifier t j  is stored within its cache. If the key identifier t j  is not cached, the client  150  may request the VKM  130  to send t j  via a message “message (params-VKM, key-name)” sent to the VKM  130 . If the client  150  determines that its cache includes the appropriate parameters, it will not send the message (params-VKM, key-name) to the VKM  130  or the message (params-PKS) to the PKS  140  and the protocol  400  will continue at step  410 . 
     At step  404 , the VKM  130  receives and may authenticate the message (params-VKM, key-name). Once authenticated, the VKM  130  may send the key identifier t j  to the client  150  (client C i ) in a message “message (RCC-Key-identifier, t j )”. 
     At step  406 , if some other cached values are not available at the client  150 , the client  150  requests the necessary values by sending a parameters request message “message (params-PKS)” to the PKS  140 . For example, the client  150  (C i ) may send the message “message (params-PKS)” to the PKS  140  to request parameters such as e.g., the blinding value b i , encrypted blinded project key and client-key w (if not cached). If the client  150  determines that its cache includes the appropriate parameters, it will not send the message (params-PKS) to the PKS  140  and the protocol  400  will continue at step  410 . 
     At step  408 , upon receiving the message (params-PKS) from the client  150  (C i ), the PKS  140  generates the blinding value b i  from    p  (i.e., b i ←   p ). The PKS  140  may also calculate e i  as the encryption of the tuple b i ·K and pks-project-key-version (i.e., e i =ENC vpk (b i ·K|pks-project-key-version) and derive a signature σ i  based on e i  (i.e., σ i =sign sk (e i )). In addition, the PKS  140  may send a message “message (Derive-Client-values, b i , e i , σ i , w)” to the client  150  (Ci) requesting that the client  150  (C i ) derive values for parameters required for subsequent steps in the process  400 . In doing so, the message (Derive-Client-values, b i , e i , σ i , w) may send parameters b i , e i , σ i , w to the client  150  (C i ). 
     At step  410 , the client  150  (Ci) has the parameters t j , b i , e i , σ i , w, as discussed above, and may record the values of these parameters in its cache memory. As part of the protocol  400 , the client  150  (Ci) may compute a derivation input such as e.g., a parameter d using a keyed hash function of the client-key w, key identifier t j , and derivation data DD (i.e., d=HKDF(w ⊕ t j , SD, 256). The client  150  (Ci) may send a message “message (Remote-derive-VKM, d, e i , σ i , key-name)” to the VKM  130  requesting that the VKM  130  derive values for parameters required for subsequent steps in the process  400 . In doing so, message (Remote-derive-VKM, d, e i , σ i , key-name) may send parameters d, e i , σ i , key-name to the VKM  130 . 
     In the illustrated embodiment, the client  150  (Ci) sending the message (Remote-derive-VKM, d, e i , σ i , key-name) is initially authenticated at the RCC  120  (at step  412 ) before the message is processed by the VKM  130 . As noted above, the RCC  120  may be implemented as part of the VKM  130 , meaning that this authentication step may be performed by the VKM  130 . At step  412 , upon receiving the message (Remote-derive-VKM, d, e i , σ i , key-name), the VKM  130  may verify the signature σ i  with the PKS&#39;s  140  vk key in e.g., an RSA signature verification process. If the signature σ i  is not verified, then the process  400  terminates. 
     If, however, the signature σ i  is verified, the VKM  130  may decrypt e i  with the VKM&#39;s  130  vsk key in e.g., an RSA decryption process to obtain the tuple b i ·K|pks-project-key-version. The VKM  130  may calculate the inverse of the b i ·K (i.e., (b i ·K) −1 ) and if it determines that the pks-project-key-version is equal to the vkm-project-key-version, it may compute z j ·b i   −1 =z j ·K·(b i ·K) −1  where z j  is the key associated with key-name. However, if the pks-project-key-version is not equal to the vkm-project-key-version, the decrypted b i ·K is multiplied by the key-update-value before computing b i   −1 =z j ·K·(b i ·K) −1 . 
     At step  416 , the RCC  120  may compute the digest parameter as the keyed hash function of v 1  and d (i.e., digest=HKDF(v j , d, 48)). The RCC  120  may also compute a modified d parameter (i.e.,  d ) as the keyed hash function of v j  and digest (i.e.,  d =HKDF(v j , digest, 2048)·z j ·b i   −1 ). In addition, the RCC  120  may send a message “message (Remote-derive-Client, digest,  d )” to the client  150  (C i ) requesting that the client compute a derived key. The message (Remote-derive-Client, digest, d) may send the parameters digest and d to the client  150  (C i ). In the illustrated embodiment, the RCC  120  is shown as performing step  416 , but it should be appreciated that this step may be performed by the VKM  130 , particularly if the RCC  120  is merged into the VKM  130 . 
     At step  418 , after receiving the message (Remote-derive-Client, digest,  d ), the client  150  (C i ) may compute the derived key dd as the has function of w ⊕ t j  and  d ·b i  (i.e., dd=HKDF((w ⊕   d ·b i , 256/128). In addition, the client  150  (C i ) may encrypt the message m using the derived key dd and store the digest and ciphertext. 
     According to the protocol  400 , blinded and or hashed derivation data DD (e.g., from the client and only known by the client) and an encrypted key (e.g., from the VKM) may be used to compute a derived key (e.g., by the RCC or VKM) that is blinded when on the RCC (or VKM). This means that the computing device implementing the VKM and RCC does not get access to or learn anything about the client&#39;s derived key, while the client does not get access to or learn anything about the server&#39;s root key. As such, privacy is ensured throughout the encryption, storage and decryption of the message m. 
     As noted above, the disclosed process  300  may also allow for a project key rotation protocol  310  ( FIG.  3   ). In one or more embodiments, a new project key may be randomly selected during the project key rotation protocol  310  (e.g., by the PKS  140 ) and is updated at the VKM  130  as discussed below. An example of the project key rotation protocol  310  is illustrated in  FIG.  5   . 
     In one or more embodiments, when the project key rotation protocol  310  is performed, the VKM  130  may contain a protected keys record comprising z j ·K and key-name, a key-update-value, and the vkm-project-key-version. In one or more embodiments, the PKS  140  may comprise the project key K and the pks-project-key-version. 
     In the illustrated protocol  310 , the PKS  140  may perform step  502  after receiving a message “message (Rotate-PSK)” to rotate the project key. In one or more embodiments, the message (Rotate-PSK) may be received from a designated client  150 . At step  502 , the PKS  140  may uniformly sample at random a project key K from    p  (i.e., K←   p ) and store the project key K. The PKS  140  may also increment the pks-project-key-version (i.e., pks-project-key-version=pks-project-key-version+1) and use pks-project-key-version to compute a transformation key and new ciphertext e k  (i.e., e k =ENC vpk (K′·K −1 |pks-project-key-version) and a new signature σ k  (i.e., σ k =sign sk (e k )). In addition, the PKS  140  may send a message “message (Rotate-VKM, e k , σ k )” to the designated client  150  with the new parameters e k , σ k . 
     At step  504 , the designated client  150  may forward the message (Rotate-VKM, e k , σ k ) to the VKM  130 . 
     In the illustrated protocol  310 , the VKM  130  may perform step  506  after receiving the message (Rotate-VKM, e k , σ k ) from the designated client  150 . At step  506 , the VKM  130  may verify the new signature σ k  with the PKS&#39;s  140  vk key in e.g., an RSA signature verification process. If the signature σ k  is not verified, then the protocol  310  terminates. 
     If the signature σ k  is verified, the VKM  130  may decrypt e k  using the VKM&#39;s  130  vsk key in e.g., an RSA decryption process to obtain the tuple K′·K −1 |pks-project-key-version. The VKM  130  may set the key-update-value equal to K′·K −1  and vkm-project-key-version equal to pks-project-key-version. The VKM  130  may update the protected keys record with the new project key and version value. That is, for each protected-key z j ·K in the record, the VKM  130  stores z j ·K′ which is equal to z j ·K·key-update-value. 
     As can be appreciated, the disclosed systems and processes provide several advantages over conventional multitenant key management services. For example, the disclosed principles use two unique features to reduce memory storage and processing load. The first feature is the use of a short header (e.g., 6 byte header). As is known in the art, a header for ciphertext is mandatory non-secret metadata that is derived together with the key and is used to re-derive the key for decryption of the ciphertext. The header is stored together with each ciphertext and must be short for minimizing storage overhead. In accordance with the disclosed principles, the header is as short as 6 bytes. For example, the header may comprise one or more parameters used from the keyed hash function as well as some data from the client or VKM. Other key management services use headers that are at least to 256 bytes or more. Considering that there may be millions of pieces of information to encrypt and de-crypt, this 40 fold reduction in the header is a significant reduction in memory and storage resources. 
     A second unique feature of the disclosed principles is the use of multiplication based derivations. Traditionally, key management services use derivation computations that utilize exponents and exponential processing, which are complex and processor intensive. By using multiplication based derivations, the disclosed principles result in tremendous efficiency improvement per key derivation operation. 
     As such, the disclosed systems, processes and protocols are an advancement in the key management services, which is necessarily rooted in computer technology. As such, the disclosed principles provide a technological solution to a technological problem by providing enhanced data and network security in a manner that also uses less memory and reduces the load on the processor in comparison to conventional key management services. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail can be made therein without departing from the spirit and scope. In fact, after reading the above description, it will be apparent to one skilled in the relevant art(s) how to implement alternative embodiments. For example, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims. 
     In addition, it should be understood that any figures which highlight the functionality and advantages are presented for example purposes only. The disclosed methodology and system are each sufficiently flexible and configurable such that they may be utilized in ways other than that shown. 
     Although the term “at least one” may often be used in the specification, claims and drawings, the terms “a”, “an”, “the”, “said”, etc. also signify “at least one” or “the at least one” in the specification, claims and drawings. 
     Finally, it is the applicant&#39;s intent that only claims that include the express language “means for” or “step for” be interpreted under 35 U.S.C. 112(f). Claims that do not expressly include the phrase “means for” or “step for” are not to be interpreted under 35 U.S.C. 112(f).