Securing implementation of a cryptographic process having fixed or dynamic keys

摘要

In the field of computer enabled cryptography, such as a keyed block cipher having a plurality of rounds, the cipher is hardened against attack by protecting the round keys by (1) combining several cipher operations using a pair of sub-keys (round keys) into one table look-up, or (2) a key masking process which obscures the round keys by providing a masked version of the key operations for carrying out encryption or decryption using the cipher. This approach is especially advantageous in an insecure “White Box” environment where an attacker has full access to execution of the cipher algorithm, including the algorithm's internal state during its execution.