Saving and Retrieving Data Based on Symmetric Key Encryption

• US 20070086588A1
• Filed: 11/08/2006
• Published: 04/19/2007
• Est. Priority Date: 04/17/2002
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: England, Paul, Peinado, Marcus
• Granted Patent: US 7,752,456 B2
• Time in Patent Office: Days
• US Class Current: 380/28
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database

Abstract

In accordance with certain aspects, data is received from a calling program. Ciphertext that includes the data is generated, using a symmetric cipher, in a manner that allows only one or more target programs to be able to obtain the data from the ciphertext. In accordance with other aspects, a bit string is received from a calling program. An identifier of the calling program is checked to determine whether the calling program is allowed to access data encrypted in ciphertext of the bit string. The integrity of the data is also verified, and the data is decrypted using a symmetric key. The data is returned to the calling program only if the calling program is allowed to access the data and if the integrity of the data is successfully verified.

Claims

1. A method, implemented in a computing device, the method comprising:

receiving data from a calling program; and

generating, using a symmetric cipher, ciphertext that includes the data, wherein the ciphertext is generated in a manner that allows only one or more target programs to be able to obtain the data from the ciphertext.

2. A method as recited in claim 1, wherein the one or more target 11 programs are identified by the calling program.

3. A method as recited in claim 1, further comprising returning the ciphertext to the calling program.

4. A method as recited in claim 1, wherein the data comprises a cryptographic key.

5. A method as recited in claim 1, wherein the one or more target programs comprises a plurality of target programs.

6. A method as recited in claim 1, wherein each of the one or more target programs is identified by a digest value generated by applying a cryptographic hash function to the target program.

7. A method as recited in claim 1, wherein the one or more target programs comprises the calling program.

8. A method as recited in claim 1, wherein receiving the data comprises receiving the data as part of a Seal operation.

9. A method as recited in claim 1, wherein generating the ciphertext comprises:

generating an identifier of the calling program;

generating a bit string which is a combination of the data, the identifier of the calling program, and identifiers of the one or more target programs; and

encrypting the bit string to generate ciphertext.

10. A method as recited in claim 1, wherein generating the ciphertext comprises:

generating a bit string which is a combination of the data, the identifier of the calling program, and identifiers of the one or more target programs; and

encrypting the bit string.

11. A method as recited in claim 9, wherein encrypting the bit string comprises using a symmetric key and a symmetric cipher to encrypt the bit string.

12. A method as recited in claim 9, further comprising:

generating a message authentication code (MAC) value for the bit string by applying a message authentication code (MAC) to the bit string; and

returning the ciphertext and the MAC value to the calling program.

13. A method as recited in claim 9, further comprising:

generating a message authentication code (MAC) value for the bit string by applying a message authentication code (MAC) to the bit string; and

wherein encrypting the bit string comprises including the MAC value in the bit string prior to encrypting the bit string.

14. A method as recited in claim 9, further comprising:

generating a message authentication code (MAC) value for the ciphertext by applying a message authentication code (MAC) to the ciphertext; and

returning the ciphertext and the MAC value to the calling program.

15. A method as recited in claim 9, wherein the identifier of the calling program comprises a digest value generated by applying a cryptographic hash function to the calling program.

16. A method as recited in claim 9, wherein the combination of the data, the identifier of the calling program, and identifiers of the one or more target programs comprises a concatenation of the data, the identifier of the calling program, and identifiers of the one or more target programs.

17. A system comprising:

means for receiving data from a calling program; and

means for using a symmetric key to generate ciphertext that includes the data, wherein the ciphertext is generated in a manner that allows only one or more target programs to be able to obtain the data from the ciphertext.

18. A method, implemented in a computing device, the method comprising:

receiving, from a calling program, a request to generate and seal data;

generating a random value to use as the data; and

generating ciphertext that includes the data, wherein the ciphertext is generated in a manner that allows only one or more target programs to be able to obtain the data from the ciphertext.