method of generating a master key from a subkey sequence for cryptographic operations, method of generating a master key from related direct and reverse sequence of subkeys for use in cryptographic operations, method of decrypting a message encrypted with a block cipher, method of processing a block cipher message having a key programming, device for generating a master key from a subkey sequence for cryptographic operations, device for processing a message with a block cipher having a key programming, computer program product, and one or more computer readable media

摘要

methods, system and devices are provided which generate a sequence of subkeys for cryptographic operations of a master key. The primary key is operated only once to generate the sequence subkeys, with a transformation comprising one or more unilateral functions. the respective bit values of the sequence subkeys are set using respective bit values of one or more unilateral functions. Advantageously, deriving subkey bits from their output bits of one or more unilateral functions removes or at least reduces correlations between the master key and subkeys, as well as between subkeys, making it more difficult or It is even impossible to retrieve the master key or other subkeys from a single subkey, for example as found using side channel attack. At the same time, by using the primary key only once (rather than using the primary key each time a subkey is generated), the vulnerability of the primary key to a side channel attack is reduced due to recovery opportunities. physical information that could lead to the discovery of the primary key would be reduced. Specific embodiments use parallel or chain execution of subfunctions to generate their subkeys. other specific realizations generate all subkeys of a single unilateral function at once.