Patent Publication Number: US-6708272-B1

Title: Information encryption system and method

Description:
TECHNICAL FIELD 
     The present invention relates to encrypting information for secure storage. 
     BACKGROUND ART 
     Increasingly, information produced by a client must be shared by other clients connected through a computer network. The information may be kept on one or more storage systems also connected to the network. Such networks often interconnect many clients throughout an organization, some of whom are excluded from access to the information. The network may also support connections to public networks, such as the Internet, providing the possibility of unauthorized access from outside of the organization. As such, interconnection networks are often untrusted. 
     Certain types of information produced and used within an organization must be kept secure. This information includes financial figures, personnel data, health information, business plans, trade secrets, and the like. A client producing such information should be able to read and write this information over an untrusted network. Further, access to this information should be restricted to only those clients with proper authorization. 
     One method to protect information is to encrypt the information using a key and then transmit the encrypted information over an untrusted network. Two types of encryption may be used, symmetric and asymmetric. In symmetric encryption, the same data key is used to encrypt and decrypt the information. Various types of symmetric encryption which are known in the art include the Data Encryption Standard (DES) algorithm as described in Federal Information Processing Standard Publication 46-1; the Improved DES (IDES) algorithm as described in U.S. Pat. No. 5,214,703 titled “Device For The Conversion Of A Digital Block And Use Of Same”; and the RC-5 algorithm as described in U.S. Pat. Nos. 5,724,428 and 5,835,600 both titled “Block Encryption Algorithm With Data-Dependent Rotations”; each of which is incorporated herein by reference. 
     In asymmetric encryption, a first key is used to encrypt the information and a second key is used to decrypt the information. Typically, the first key is a public key which may be widely known and the second key is a private key which is known only to authorized clients. Various forms of asymmetric encryption are known in the art, including the Diffie-Hellmean algorithm as described in U.S. Pat. No. 4,200,770 titled “Cryptographic Apparatus And Method”; and U.S. Pat. No. 4,405,829 titled “Cryptographic Communications System And Method”; each of which is incorporated by reference herein. 
     A technique for sending information over an untrusted network is end-to-end encryption. A host or storage server sends a data key to the client encrypted using a client key which is secret to the host and the client. The client decrypts the data key and holds the data key in a protected region of memory. Data transferred between the host and the client is encoded at one end and decoded at the other end using the data key. The data key is used throughout the entire information access session. 
     End-to-end encryption has several problems. First, the client key must be known by both the host and the client. Second, because the protected region of memory is part of the client, an imposter client may access protected information. The imposter client may have a stolen client key or may be a client for whom access privileges have been revoked. Third, because the client decrypts the data key and the data, the decrypted data key may be accessible through an attack at the operating system level. 
     DISCLOSURE OF INVENTION 
     It is an object of the present invention to separate the client from client-side encryption and decryption. 
     It is another object of the present invention to permit a client access to information over an untrusted network without permitting the clients to have direct contact with encryption and decryption keys. 
     Still another object of the present invention is to permit a client to access information over an untrusted network without having the client handle encrypted information. 
     Yet another object of the present invention is to permit a client to access information over an untrusted network without having the client carry out the encrypting or decrypting process. 
     A further object of the present invention is to provide secure access to data held on storage devices. 
     In carrying out the above objects and other objects and features of the present invention, an information encryption system is provided. The information encryption system includes at least one client for processing information. The system also includes at least one storage device for holding the information. At least one key server provides a data key for encrypting and decrypting the information. An encryption module is associated with each client. Each encryption module has a first processor accessing a first memory and a second processor accessing a second memory different from the first memory. The first processor communicates with the associated client. The second processor communicates with the storage device. The first processor communicates with the second processor through a dedicated channel. The second processor obtains the data key from the key server. Information is received from the first processor over the dedicated channel and encrypted using the data key. The encrypted information is then stored on the storage device. The second processor also reads the encrypted information from the storage device, decrypts the information using the data key, and sends the decrypted information to the first processor over the dedicated channel. 
     In an embodiment of the present invention, each client has a private key and a matching public key such that data encoded with the client public key can only be decoded with the client private key. The client private key may be held by the second processor or may be read by the second processor from a key reader. 
     In another embodiment of the present invention, the key server receives a request from an encryption module to access encrypted information, the request including the client public key. The key server determines if the associated client has access to the encrypted information. If the client has access, the data key is encrypted using the client public key. The encrypted data key is sent to the requesting encryption module. The second processor receives the encrypted data key and decrypts the encrypted data key with the client private key. 
     In yet another embodiment of the present invention, the encryption module is a printed circuit card that can be inserted into a card slot in the client processor. In a refinement, the client includes a driver for accessing the encryption module. The driver includes a first logical portion in communication with a second logical portion. The first logical portion provides the client interface to the driver. The second logical portion controls communication with the first processor. 
     In a further embodiment of the present invention, the second processor functions as the key server. 
     An information encryption module is also provided. The module includes a first processor in communication with the client. A first memory, accessible by the first processor, holds unencrypted information. A second processor communicates with at least one storage device and a key server. The second processor is connected to the first processor through a dedicated channel. The second processor decrypts the data key and encrypts and decrypts information with the decrypted data key. A second memory, accessible by the second processor, holds encrypted information. 
     A method is also provided for writing information in an encrypted format to at least one storage device. A data key is obtained. A request is received from the client to store information. Unencrypted information is written to a first memory. The unencrypted information is encrypted using the data key. The encrypted information is written to a second memory not accessible by the client. The encrypted information is sent from the second memory to the storage device. 
    
    
     The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a schematic diagram of an encryption system according to an embodiment of the present invention; and 
     FIG. 2 is a schematic diagram of an encryption module according to an embodiment of the present invention. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Referring to FIG. 1, a schematic diagram of an encryption system according to an embodiment of the present invention is shown. Information encryption system  20  includes at least one client  22  connected through encryption module  24  to at least one storage device. Storage devices may be disks, tapes, drums, integrated circuits, or the like, operative to hold data by any means, including magnetically, electrically, optically, and the like. Storage devices may be arranged in a storage area network, shown generally by  26 , which may include storage devices  28  accessed through storage server  30  or directly accessed storage device  32 . Storage area network  26  may be part of or may be accessed through interconnection network  34 . Encryption module  24  may be connected to interconnection network  34  through network connection  36 . Typically, interconnection network  34  is untrusted in that transmissions through interconnection network  34  may be surreptitiously monitored. 
     Key server  38  may also be connected to network  34 . Key server  38  provides data keys for encrypting and decrypting information. Key server  38  may encrypt the data key for transmission over untrusted network  34 , as will be described below. In an embodiment of the present invention, one or more storage servers  30  can function as key server  38 . 
     Encryption module  24  includes first processor  40  in communication with client  22 . First processor  40  accesses first memory  42 . Encryption module  24  also includes second processor  44  in communication with at least one storage device  28 , 32 . Second processor  44  accesses second memory  46 . Second memory  46  is separate and distinct from first memory  42 . Second memory  46  is not in the memory space of first processor  40 , nor is first memory  42  in the memory space of second processor  44 . First processor  40  and second processor  44  communicate through dedicated channel  48  using messages. Dedicated channel  48  is the only means through which information passes between first processor  40  and second processor  44 . 
     First processor  40  handles unencrypted information and stores this unencrypted information in first memory  42 . Second processor  44  obtains a data key from key server  38 . Second processor  44  receives unencrypted information from first processor  40  over dedicated channel  48 . Second processor  44  encrypts the information using the data key and stores the encrypted information on at least one storage device  28 , 32 . Second processor  44  can also read encrypted information from at least one storage device  28 , 32 . Second processor  44  decrypts the information using the data key and sends the decrypted information to first processor  40  over dedicated channel  48 . 
     In a preferred embodiment of the present invention, second processor  44  accesses key reader  50 . Each user of client  22  is issued an external storage medium device, such as a “smart card”, onto which is written a client private key and matching client public key. Second processor  44  reads client private and public keys through key reader  50 . When encrypted data is to be sent, either by reading or writing, second processor  44  forwards the client public key to key server  38 . When key server  38  receives a request from encryption module  24  to access encrypted information, key server  38  first determines if the associated client  22  has access to the encrypted information. If client  22  has been granted access, key server  38  encrypts the data key with the public key of client  22 . The encrypted data key is then sent by key server  38  to encryption module  24 . Second processor  44  receives the encrypted data key and decrypts the encrypted data key using the private key for client  22 . Second processor  44  can then use the decrypted data key to encrypt information for transmission over interconnection network  34  or decrypt information received through interconnection network  34 . 
     In an embodiment of the present invention, determining access to encrypted information includes several verification checks. Second processor  44  sends an access request to key server  38  including an identification for client  22 , the public key for client  22 , and an identification for the processor being used by client  22 . When key server  38  receives the access request, an Access Control List (ACL) is checked to verify that client  22  is authorized to receive encrypted information. Additionally, the ACL is checked to verify that the processor used by client  22  has the proper security to receive encrypted data. 
     In an embodiment of the present invention, storage device  52  is directly connected to encryption module  24  through second processor  44 . Storage device  52  performs the same functions as storage devices  28 , 32  described above. Second processor  44  functions in the manner described above to write encrypted information into and read encrypted information from storage device  52 . In a refinement, encryption module  24  is not connected to network  34 . Second processor  44  is then further operative to perform the functions described for key server  38 . A portion of second memory  46  is non-volatile, permitting second processor  44  to store data keys and ACL in a secure location. 
     Referring now to FIG. 2, a schematic diagram of an encryption module according to an embodiment of the present invention is shown. Encryption module  24  is implemented as a printed circuit card which may be inserted into a computer associated with client  22 . PCI connector  60  on encryption module  24  plugs into PCI bus  62  in the client computer system, connecting client system PCI bus  62  with primary PCI bus  64 . First processor  40  uses primary PCI bus  64  to communicate with client  22 . 
     First processor  40  communicates with first memory  42  and first BIOS  64  through first local bus  66 . Second processor  44  is connected to first processor  40  through dedicated channel  48  implementing a secondary PCI bus. Second memory  46  and second BIOS  68  are connected to second processor  44  through second local bus  70 . 
     Encryption module  24  may include network interface  72  connected to second processor  44  through second local bus  70 . Network interface  72  connects to network connection  36  through network connector  74 . Network interface  72  and network connector  74  may be adapted to one or more of a wide variety of networks, including local area networks, storage area networks, wide area networks, the Internet, and the like, using a wide variety of interconnection media, such as, for example, twisted pair, coaxial cable, optical fiber, and the like. 
     Encryption module  24  may also include storage controller  76  connected to second processor  44  through second local bus  70 . Storage controller  76  is directly connected to one or more storage devices  52  through storage connector  78 . Storage controller  76  and storage connector  78  may be adapted to handle one or more common storage interconnection schemes, including SCSI, Fiber Channel, high speed parallel, and the like. Directly connected storage devices  52  may include one or more of disks, tapes, drums, optical devices, solid-state memory, and the like. 
     Encryption module  24  may further include key reader interface  80  connected to second processor  44  through second local bus  70 . Key reader interface  80  is connected to key reader  50  through key connector  82 . In a preferred embodiment, key reader  50  reads a public key and a private key from a “smart card” inserted into key reader  50  for each user of client  22 . 
     In a preferred embodiment, first processor  40  and second processor  44  are each implemented using an i80960 RN I/O processor from Intel Corporation. The i80960 RN processor includes a PCI-to-PCI bridge forming an interconnection path between two independent 64-bit PCI busses. The i80960 RN implementing first processor  40  is configured to hide second processor  44  from client  22 . This configuration permits second processor  44  to have an independent and separate memory space. Each i80960 RN processor has an internal memory controller unit permitting devices connected to local bus  66 , 70  to appear in the private processor memory space of respective processor  40 , 44 . First memory  42  and second memory  46  are implemented with 72-bit wide SDRAM modules including error detection and correction capabilities. 
     In an embodiment of the present invention, encryption module  24  is built to an open system standard. Client  22  includes a driver for accessing encryption module  24 . The driver includes a first logical portion in communication with a second logical portion. The first logical portion provides client  22  with an interface to the driver. The second logical portion controls communication with first processor  40 . 
     While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.