A METHOD AND DEVICE FOR EXECUTING A DECRYPTING MECHANISM THROUGH CALCULATING A STANDARDIZED MODULAR EXPONENTIATION FOR THWARTING TIMING ATTACKS

• Main Authors: HOLLMANN, HENDRIK, DIRK, LODEWIJK, VAN DIJK, MARTEN, ERIK, LENOIR, PETRUS, JOHANNES
• Format: Patent
• Language: English; French; German
• Published: 01.09.1999
• Edition: 6
• Subjects: ADVERTISING; CALCULATING; CODING OR CIPHERING APPARATUS FOR CRYPTOGRAPHIC OR OTHERPURPOSES INVOLVING THE NEED FOR SECRECY; COMPUTING; COUNTING; CRYPTOGRAPHY; DISPLAY; EDUCATION; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRIC DIGITAL DATA PROCESSING; ELECTRICITY; JAMMING OF COMMUNICATION; PHYSICS; SEALS; SECRET COMMUNICATION; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

An encrypting exponentiation modulo M is effected by a modular multiplication X*YmodM, where M is a temporally steady but instance-wise non-uniform modulus. The method involves an iterative series of steps. Each step executes one or two first multiplications to produce a first result, and a trim-down reduction of the size of the first result by one or more second multiplications to produce a second result. The method furthermore takes a distinctive measure for keeping the final result of each step below a predetermined multiplicity of the modulus. In particular, the method postpones substantially any subtraction of the modulus as pertaining to the measure to a terminal phase of the modular exponentiation. This is possible through choosing in an appropriate manner one or more parameters figuring in the method. This further maintains overall temporal performance.