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Protecting modular exponentiation in cryptographic operations

A modular exponentiation and modular protection technology, applied in the field of hiding the intermediate results of modular exponentiation, can solve problems such as poor environment

Inactive Publication Date: 2013-07-24
NAGRAVISION SA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In this case, it is a worse environment than the gray box model since the attacker has full access to the software internals

Method used

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  • Protecting modular exponentiation in cryptographic operations

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Embodiment Construction

[0042] The invention describes a protection method for modular exponentiation using the so-called window method in an open software environment. By opening the software environment, we assume a binary code executed on said PC system and accessible by an attacker.

[0043] like figure 1 As shown, the invention may be implemented in a processing unit dedicated to performing cryptographic operations. This unit includes at least: a processor CPU capable of executing a software core; and a memory MEM1 for storing the code and providing necessary space for storing temporary data MEM2. An interface INT is provided in order to receive messages for encrypted processing encrypted (or decrypted) for storage in the temporary memory MEM2. This interface INT also sends decrypted (or encrypted) messages to other components of the receiving device in the same way.

[0044] According to a preferred embodiment, we consider a PC system or a processing unit performing said modular exponentiati...

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Abstract

The present invention proposes a method for executing a blinded modular exponentiation, based on a window method with a window size of k bits so using 2 k pre-calculated variables (Y i = X i mod N for i = 0 to 2 k -1), on input data X of n bits to obtain output data S of n bits, S = X d mod N, where d is the exponent of size m bits and N is the modulus of n bits, comprising the steps of: —� blinding the pre-calculated variables by a blinding value B 1 being a pseudo-random variable of the size of the modulus (n bits) and lower than the modulus (Y i =Y ¡ × B 1 mod N for i = 0 to 2 k -1) —� executing the modular exponentiation with the blinded pre-calculated variables, to obtain an intermediate result (A), —� unblinding the intermediate result by a unblinding value C 1 =(B 1 g ) -1 mod N where g equals the concatenation of m / k times the value "1" coded on k bits, to obtain the output data S.

Description

technical field [0001] The present invention relates to software and data encryption. In particular, the invention relates to a method for hiding intermediate results of modular exponentiation. Background technique [0002] Until recently, cryptography was only concerned with the protection of message delivery in hostile environments. In the traditional scheme (aka black box model), the attacker only has access to the input of the decryption device. With the advent of pay TV, DRM-protected digital content (smartphones, PCs or movies, music on CD / DVD), the current attacker actually has access to the decryption device and its output, which means that he can not only passively Study the state and intermediate values ​​of encrypted devices, but also actively intervene in their calculations. [0003] Specifically, the concept of failure analysis emerged in 1996: when a decryption device is submitted to an abnormal condition (input error, abnormal temperature, strong electromag...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F7/72
CPCH04L9/0816G06F7/723G06F2207/7238
Inventor R·贝文
Owner NAGRAVISION SA