CRYPTOGRAPHIC SYSTEM

• US 20110116625A1
• Filed: 03/02/2009
• Published: 05/19/2011
• 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: Gorissen, Paulus M.H.M.A., Michiels, Wilhelmus P.A.J.
• Granted Patent: US 9,710,623 B2
• Time in Patent Office: Days
• US Class Current: 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 cryptographic system, comprising:

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.

2. The cryptographic system according to claim 1, wherein the combining operation comprises combining an outcome of the cryptographic algorithm with an outcome of the function.

3. The cryptographic system according to claim 1, wherein 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.

4. The cryptographic system according to claim 1, wherein given a particular value of an outcome of the function, the combining operation defines a one-to-one correspondence between the outcome of the cryptographic algorithm and an outcome of the combining operation.

5. The cryptographic system according to claim 1, further comprising a signal generator for generating a signal comprising a representation of an outcome of the combining operation.

6. The cryptographic system according to claim 5, wherein the signal generator is arranged for including in the signal a representation of an input to the first function.

7. The cryptographic system according to claim 6, wherein the implementation of the combining operation is arranged for combining a single outcome of the function with a plurality of outcomes of the cryptographic algorithm.

8. The cryptographic system according to claim 7, further comprising a signal generator for generating a signal comprising a value representing an input to the first function and the plurality of outcomes of the second function.

9. The cryptographic system according to claim 1, wherein the white-box implementation comprises a look-up table and an XOR operation.

10. The cryptographic system according to claim 1, wherein the white-box implementation comprises

means for accessing data identifying a device and/or a user to obtain identification data, and

means for establishing the output of the function in dependence on the identification data.

11. A cryptographic system, comprising an encrypter comprising:

an implementation of a first function;

an implementation of a first cryptographic algorithm; and

an implementation of a first combining operation for establishing encrypted data in dependence on an outcome of the first function and in dependence on an outcome of the first cryptographic algorithm;

an output for providing information representing an outcome of the first combining operation to a decrypter;

the cryptographic system further comprising the decrypter comprising;

an input for obtaining the information representing the outcome of the first combining operation;

an implementation of a second function, arranged for applying the second function to a value corresponding to the input to the first function;

an implementation of a second cryptographic algorithm, arranged for applying the cryptographic algorithm to data based on at least part of the information representing the outcome of the first combining operation; and

an implementation of a second combining operation for establishing decrypted data in dependence on an outcome of the second function and in dependence on an outcome of the second cryptographic algorithm;

wherein at least one of the following implementations comprises a white-box implementation;

the implementation of the first function and the implementation of the second function.

12. A method of cryptographic processing, comprising

applying a function to a first value by means of a white-box implementation thereof;

applying a cryptographic algorithm to a second value; and

applying 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.

13. A computer program product comprising instructions stored on a non-transitory computer readable medium for causing a processor to perform the method according to claim 12.