Cryptographic system

• US 9,710,623 B2
• Filed: 03/02/2009
• Issued: 07/18/2017
• Est. Priority Date: 03/05/2008
• Status: Active Grant

• Current Assignee: Irdeto B.V. (MultiChoice Group Ltd.)
• Original Assignee: Irdeto B.V. (MultiChoice Group Ltd.)
• Inventors: Michiels, Wilhelmus P. A. J., Gorissen, Paulus M. H. M. A.
• Primary Examiner(s): Pearson, David
• Assistant Examiner(s): PLECHA, THADDEUS J
• Application Number:
  US12/921,075
• Publication Number:
  US 20110116625A1
• Time in Patent Office: 3,060 Days
• Field of Search: 380 28
• CPC Class Codes: G06F 21/14 against software analysis or reverse engineering, e.g. by obfuscation
• CPC Class Codes: H04L 2209/16 Obfuscation or hiding, e.g. involving white box
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 9/06 the encryption apparatus using shift registers or memories for block-wise or stream coding, e.g. DES systems or RC4; Hash functions; Pseudorandom sequence generators
• CPC Class Codes: H04L 9/0618 Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation
• CPC Class Codes: H04L 9/0631 Substitution permutation network [SPN], i.e. cipher composed of a number of stages or rounds each involving linear and nonlinear transformations, e.g. AES algorithms

Abstract

A cryptographic system comprises a white-box implementation of a function; an implementation of a cryptographic algorithm; and an implementation of a combining operation for establishing cryptographically processed data in dependence on an outcome of the function and in dependence on an outcome of the cryptographic algorithm. The combining operation comprises combining an outcome of the cryptographic algorithm with an outcome of the function. Alternatively, the combining operation comprises combining an outcome of the function with a received data element to obtain a combination outcome and applying the cryptographic algorithm to the combination outcome.

Claims

1. A method comprising:

selecting a cryptographic algorithm for which a white-box implementation is not known; and

configuring a computer processor to provide a white-box implementation of a cryptographic system that implements the selected cryptographic algorithm, said configuring comprising configuring the computer processor to execute one or more instructions that cause the computer processor to perform;

a white-box implementation of a function, wherein the white-box implementation of the function is configured for accessing data identifying at least one of a device and a user to obtain identification data, and establishing an outcome of the function in dependence on the identification data;

an implementation of the selected cryptographic algorithm;

an implementation of a combining operation for establishing cryptographically processed data in dependence on a single outcome of the function and in dependence on a plurality of outcomes of the cryptographic algorithm, the combining operation comprising combining the plurality of outcomes of the cryptographic algorithm with the single outcome of the function; and

an implementation of a signal generator for generating a signal comprising a representation of an outcome of the combining operation.

2. The method according to claim 1, wherein given a particular value of the single outcome of the function, the combining operation defines a one-to-one correspondence between the plurality of outcomes of the cryptographic algorithm and the outcome of the combining operation.

3. The method according to claim 1, wherein the signal generator is arranged for including in the signal a representation of an input to the function.

4. The method according to claim 1, wherein the signal generated by the signal generator comprises a representation of an input to the function and representations of the plurality of outcomes of the cryptographic algorithm.

5. The method according to claim 1, wherein the white-box implementation of the function comprises a look-up table and an XOR operation.

6. The method according to claim 1, wherein the one or more instructions cause the computer processor to generate a reproducible input, the white-box implementation of the function being implemented using the input.

7. The method according to claim 1, wherein the one or more instructions cause the computer processor to generate a non-random input, the white-box implementation of the function being implemented using the input.

8. The method according to claim 1, wherein the one or more instructions cause the computer processor to combine the plurality of outcomes of the cryptographic algorithm with the single outcome of the function using at least one of XOR and a modulo operation.

9. A method of cryptographic processing, which is implemented by a computer, comprising:

applying a function to a first value by a white-box implementation of the function, wherein the applying the function to the first value by the white-box implementation comprises accessing data identifying at least one of a device and a user to obtain identification data, and establishing an outcome of the function in dependence on the identification data;

applying a cryptographic algorithm to a second value;

applying a combining operation for establishing cryptographically processed data in dependence on a single outcome of the function and in dependence on a plurality of outcomes of the cryptographic algorithm, wherein the applying the combining operation comprises combining the plurality of outcomes of the cryptographic algorithm with the single outcome of the function; and

generating a signal comprising a representation of an outcome of the combining operation.

10. The method according to claim 9, wherein given a particular value of the single outcome of the function, the combining operation defines a one-to-one correspondence between the plurality of outcomes of the cryptographic algorithm and the outcome of the combining operation.

11. The method according to claim 9, wherein the generating the signal comprises including in the signal a representation of an input to the first function.

12. The method according to claim 9, wherein the generating step further comprises including in the signal a representation of an input to the function and the plurality of outcomes of the cryptographic algorithm.

13. The method according to claim 9, wherein the white-box implementation comprises a look-up table and an XOR operation.

14. An non-transitory computer readable recording medium having recorded thereon a computer program comprising instructions for causing a processor to perform a method of cryptographic processing, the method comprising:

applying a function to a first value by a white-box implementation of the function, wherein the applying the function to the first value by the white-box implementation comprises accessing data identifying at least one of a device and a user to obtain identification data, and establishing an outcome of the function in dependence on the identification data;

applying a cryptographic algorithm to a second value;

applying a combining operation for establishing cryptographically processed data in dependence on a single outcome of the function and in dependence on a plurality of outcomes of the cryptographic algorithm, wherein the applying the combining operation comprises combining the plurality of outcomes of the cryptographic algorithm with the single outcome of the function; and

generating a signal comprising a representation of an outcome of the combining operation.

15. A system arranged comprising a hardware processor arranged to perform a method of cryptographic processing, the method comprising:

applying a function to a first value by a white-box implementation of the function, wherein the applying the function to the first value by the white-box implementation comprises accessing data identifying at least one of a device and a user to obtain identification data, and establishing an outcome of the function in dependence on the identification data;

applying a cryptographic algorithm to a second value;

applying a combining operation for establishing cryptographically processed data in dependence on a single Outcome of the function and in dependence on a plurality of outcomes of the cryptographic algorithm, wherein the applying the combining operation comprises combining the plurality of outcomes of the cryptographic algorithm with the single outcome of the functions; and

generating a signal comprising a representation of an outcome of the combining operation.