Patent ID: 9735956
Date: 2017-08-15
CPC Classifications: G06F,G09C,H04L

Claim:
1. A method comprising: receiving a first input comprising a first decryption key and a second input comprising an encrypted second decryption key at a cryptographic decryption apparatus, wherein the encrypted second decryption key is to be decrypted by the cryptographic decryption apparatus according to the first decryption key, wherein the second input comprises the key ladder length as a part of the encrypted second decryption key decrypted by the cryptographic decryption apparatus; storing a value of the key ladder length in a first register by a cryptographic processor; and using the stored value as a loop index by the cryptographic processor for a number of iterations of the cryptographic decryption apparatus executed as a loop, wherein at one stage in execution of the loop of the cryptographic decryption apparatus, the second input comprises the key ladder length, wherein the execution of the loop of the cryptographic decryption apparatus operates for the number of iterations equal to an initial value of the loop index, wherein an output from a previous iteration of the loop comprises the first input to the cryptographic decryption apparatus for a following iteration of the loop.