Systems and methods for protecting data secrecy and integrity

• US 7,940,928 B2
• Filed: 02/29/2008
• Issued: 05/10/2011
• Est. Priority Date: 12/22/1999
• Status: Expired due to Fees

• Current Assignee: Intertrust Technologies Corporation (Fidelio Acquisition Co LLC)
• Original Assignee: Intertrust Technologies Corporation (Fidelio Acquisition Co LLC)
• Inventors: Sibert, W. Olin
• Primary Examiner(s): Lanier; Benjamin E
• Application Number:
  US12/040,738
• Publication Number:
  US 20090010423A1
• Time in Patent Office: 1,166 Days
• Field of Search: 713/161, 713/168, 713/170
• US Class Current: 380/28
• CPC Class Codes: G06F 21/606 by securing the transmission between two devices or processes
• CPC Class Codes: G06F 21/6209 to a single file or object, e.g. in a secure envelope, encrypted and accessed using a key, or with access control rules appended to the object itself
• CPC Class Codes: G06F 21/64 Protecting data integrity, e.g. using checksums, certificates or signatures
• CPC Class Codes: G06F 2221/2107 File encryption
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 63/123 received data contents, e.g. message integrity
• CPC Class Codes: H04L 9/0625 with splitting of the data block into left and right halves, e.g. Feistel based algorithms, DES, FEAL, IDEA or KASUMI
• CPC Class Codes: H04L 9/0637 Modes of operation, e.g. cipher block chaining [CBC], electronic codebook [ECB] or Galois/counter mode [GCM]
• CPC Class Codes: H04L 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC

Abstract

A technique for integrating message authentication with encryption and decryption is disclosed. Intermediate internal states of the decryption operation are used to generate a validation code that can be used to detect manipulation of the encrypted data. The technique is optimized with respect to processing time, execution space for code and runtime data, and buffer usage. The technique is generally applicable to a variety of block ciphers, including TEA, Rijndael, DES, RC5, and RC6.

Claims

1. A method of generating a cryptographic validation value for use in authenticating data, the method performed by a computer system comprising a processor and a memory encoded with program instructions that, when executed by the processor, cause the system to perform the method, the method including:

receiving a piece of encrypted data;

obtaining an input validation value from the encrypted data;

dividing, by the processor, the input validation value into a first segment and a second segment;

using at least a first function to combine the first segment with a first input from a cryptographic cipher function, whereby the first function produces a first result;

using at least a second function to combine the second segment with a second input from the cryptographic cipher function, whereby the second function produces a second result;

generating, by the processor, a first transformed result by performing at least a first transformation on a first value, the first value being derived, at least in part, from the first result;

generating, by the processor, a second transformed result by performing at least a second transformation on a second value, the second value being derived, at least in part, from the second result;

forming, by a processor, an output validation value by combining a third segment and a fourth segment, the third segment being derived, at least in part, from the first transformed result, and the fourth segment being derived, at least in part, from the second transformed result; and

using the output validation value to authenticate the piece of encrypted data.

2. The method of claim 1, in which the third segment is further derived, at least in part, from the second segment, and in which the fourth segment is further derived, at least in part, from the first segment.

3. The method of claim 2, in which the fourth segment is further derived, at least in part, from the first input from the cryptographic cipher function.

4. The method of claim 1, in which the first function comprises a logical exclusive-or, and in which the second function comprises an addition function.

5. The method of claim 1, in which the first and second transformations include at least one bit-wise rotation operation.

6. The method of claim 1, in which the first and second transformations include at least one logical exclusive-or operation.

7. The method of claim 1, in which the first and second transformations include a bit-wise rotation operation, a logical exclusive-or operation, and an addition operation.

8. The method of claim 1, in which the cryptographic cipher function comprises an implementation of the Tiny Encryption Algorithm.

9. The method of claim 1, in which the cryptographic cipher function comprises a Rijndael block cipher.

10. The method of claim 1, wherein the memory is further encoded with executable program instructions that, when executed by the processor cause the processor to perform a method further including the steps of:

dividing, by the processor, the output validation value into a fifth segment and a sixth segment;

using at least a third function to combine the fifth segment with a third input from the cryptographic cipher function, whereby the third function produces a third result;

using at least a fourth function to combine the sixth segment with a fourth input from the cryptographic cipher function, whereby the fourth function produces a fourth result;

generating, by the processor, a third transformed result by performing at least a third transformation on a third value, the third value being derived, at least in part, from the third result;

generating, by the processor, a fourth transformed result by performing at least a fourth transformation on a fourth value, the fourth value being derived, at least in part, from the fourth result;

forming, by the processor, a-second output validation value by combining a seventh segment and an eighth segment, the seventh segment being derived, at least in part, from the third transformed result, and the eighth segment being derived, at least in part, from the fourth transformed result; and

using the second output validation value to authenticate the piece of encrypted data.

11. A system for generating a cryptographic validation value for use in authenticating data, the system including:

a port for obtaining an input validation value;

one or more processing units, the one or more processing units dividing the input validation value into a first segment and a second segment;

a first function for combining the first segment with a first input from a cryptographic cipher function, whereby the first function produces a first result; and

a second function for combining the second segment with a second input from the cryptographic cipher function, whereby the second function produces a second result;

wherein the one or more processing units generates a first transformed result by performing at least a first transformation on a first value, the first value being derived, at least in part, from the first result;

wherein the one or more processing units generates a second transformed result by performing at least a second transformation on a second value, the second value being derived, at least in part, from the second result; and

wherein the one or more processing units forms an output validation value by combining a third segment and a fourth segment, the third segment being derived, at least in part, from the first transformed result, and the fourth segment being derived, at least in part, from the second transformed result.

12. The system of claim 11, wherein the one or more processing units implements one or more of the first function and the second function.

13. The system of claim 11, in which the third segment is further derived, at least in part, from the second segment, and in which the fourth segment is further derived, at least in part, from the first segment.

14. The system of claim 13, in which the fourth segment is further derived, at least in part, from the first input from the cryptographic cipher function.

15. The system of claim 11, wherein at least one of the first function and the second function comprises at least one of a logical exclusive-or function and an addition function.

16. The system of claim 11, wherein at least one of the first transformation and the second transformation comprises at least one of a logical exclusive-or operation, a bit-wise rotation operation, and an addition operation.

17. The system of claim 11, wherein the cryptographic cipher function comprises an implementation of the Tiny Encryption Algorithm.

18. The system of claim 11, wherein the cryptographic cipher function comprises a Rijndael block cipher.

19. The system of claim 11, further including:

the one or more processing units dividing the output validation value into a fifth segment and a sixth segment;

a third function for combining the fifth segment with a third input from the cryptographic cipher function to produce a third result; and

a fourth function for combining the sixth segment with a fourth input from the cryptographic cipher function to produce a fourth result;

wherein the one or more processing units generate a third transformed result by performing at least a third transformation on a third value, the third value being derived, at least in part, from the third result;

wherein the one or more processing units generates a fourth transformed result by performing at least a fourth transformation on a fourth value, the fourth value being derived, at least in part, from the fourth result; and

wherein the one or more processing units forms a second output validation value by combining a seventh segment and an eighth segment, the seventh segment being derived, at least in part, from the third transformed result, and the eighth segment being derived, at least in part, from the fourth transformed result.

20. The system of claim 19, wherein the one or more processing units implements at least one of the third function and the fourth function.