Patent ID: 7227951

Claim:
A forward secure ANSI X9.17 pseudorandom number generator, comprising a processor which executes instructions for implementing a state machine having: an iteration integer i, which takes on integer values that satisfy i>0; a key K; a current state As i−1 for each iteration integer i; an enhanced keyed block cipher F′ K , wherein the enhanced block cipher F′ K is a function obtained by combining a block cipher F K with its input value; an enhanced next state As′ i for each iteration integer I, given by As′ i =F′ K (As i−1 ); and an enhanced pseudorandom number generator output Ay′ i for each iteration integer i, wherein the enhanced pseudorandom number generator output Ay′ i is a function of at least one auxiliary input t i , given by Ay′ i =F′ K (F′ K (t i ) ⊕As i−1 ).