| 摘要 |
The invention relates to methods for an espionage-protected determination of the modular inverse b of a value a to the modulus n for a cryptographic application. According to said method, an auxiliary value beta and an auxiliary modulus delta are determined at least in accordance with the value a , the modulus n and also at least one masking parameter r , an auxiliary inverse beta ' is determined as the modular inverse of the auxiliary value beta to the auxiliary modulus delta and the modular inverse b is determined at least in accordance with the auxiliary inverse beta ', the masking parameter(s) r and the auxiliary value beta and/or the auxiliary modulus delta . The invention also relates to a corresponding computer program product and a portable data carrier. The invention provides a modular inversion method that is protected against espionage, which is suitable for security-critical applications, e.g. cryptographic calculations in a portable data carrier. |
