Patent ID: 8515057

Claim:
A method of executing a cryptographic calculation in an electronic component that executes at least one secret-key operation to be carried out on a data block with a secret cryptographic key comprising m secret cryptographic key blocks of n bits, and executes a nonlinear operation, wherein the method of executing the cryptographic calculation causes the electronic component to leak a signal corresponding to a current consumed by the electronic component or corresponding to an electromagnetic field generated by the electronic component when the electronic component is of executing the cryptographic calculation, the method comprising modifying the leaked signal during executing the cryptographic calculation, so as to reduce correlation between the leaked signal and the secret key operation, wherein modifying the leak is accomplished by modifying the manner in which executing the cryptographic calculation is executed, the method comprising: for a given secret cryptographic key block, using the electronic component to perform the method including: determining 2 n −1 additional and different secondary secret keys on n bits, each additional and different secondary secret key being different from said secret cryptographic key block; carrying out, in addition to said secret-key operation with said secret cryptographic key block, 2 n −1 secret-key operations with said secondary secret keys on a data block, and obtaining respectively an encrypted data block being encrypted with said secret cryptographic key block and additionally 2 n −1 encrypted secondary data blocks encrypted with said respective secondary secret keys; carrying out said nonlinear operation on said encrypted data block and in addition carrying out 2 n −1 nonlinear operations on said secondary encrypted data blocks; discarding the 2 n −1 results of the 2 n −1 additional non-linear operations, and providing a resultant encrypted data block on the basis of the encrypted data block.