Patent ID: 9515818
Filing Date: 2016-12-06
CPC Classification: H04L

Claim Text:
1. A method for performing a block cryptographic operation comprising a plurality of rounds, the method comprising: receiving a message comprising a plurality of blocks; identifying a set of round-specific keys for use in a cryptographic operation to apply to the message; selecting a set of the blocks, the set having a particular number of blocks of the message; and in order to increase protection against whitebox attackers attempting to access the message, applying the cryptographic operation, using the identified set of keys, to the selected set of blocks, wherein a first particular round of the cryptographic operation for a first block of the message in the set is performed using a first round-specific key after a later round than the first particular round is performed using the first round-specific key for a second block of the message in the set, and a second particular round for the first block is performed using a second round-specific key before an earlier round than the second particular round for the second block is performed using the second round-specific key.