Patent ID: 9559844
Date: 2017-01-31
CPC Classifications: H04L

Claim:
1. A non-linear processor that subjects an input value from a feedback shift register to non-linear processing to output a key stream, the feedback shift register maintaining an internal state of a stream cipher initialized based on a secret key and an initial vector or an internal state of the stream cipher updated upon output of a key stream, the non-linear processor comprising program execution circuitry operative to store and execute a computer program to form functional components including: a non-linear substitution unit that subjects the input value to non-linear substitution processing; a plurality of internal registers that store output values from the non-linear substitution unit; a mask processing unit that is provided at an input end of each of the plurality of internal registers and carries out an exclusive-OR operation of a random number generated from part of values stored in the feedback shift register and the output value of the non-linear substitution unit to mask the output value of the non-linear substitution unit; and an unmasking unit that is provided at an output end of each of the plurality of internal registers and carries out an exclusive-OR operation of the random number and the value stored in each of the plurality of internal registers to unmask the value stored in the internal register; wherein the plurality of internal registers are connected via the non-linear substitution unit, and the non-linear substitution unit carries out the non-linear substitution processing while at least using the value stored in the internal register as the input value.