Method for updating a linear feedback shift register of code generator

Abstract

The invention relates to three different methods for updating a linear feedback shift register of a code generator, and code generators applying the methods. In the basic method a Galois-type linear feedback shift register of a code generator is updated to a target state which is at a known offset from a unit state. The basic method comprises the following: ( ) generating a binary offset number illustrating the offset; ( ) generating a counter showing the number of bits in the binary offset number; ( ) initializing a temporary state with the unit state; ( ) iterating as long as the counter value is higher than zero: ( ) multiplying the temporary state by itself by applying a Galois Field multiplication; ( ) shifting the temporary state one state forward from the current temporary state if the value of the bit shown by the counter is one; and ( ) decrementing the counter value by one; ( ) in the end, when the counter has reached the value zero, setting the temporary state as the target state. The described basic method is also employed in methods for updating a Galois-type/Fibonacci-type linear feedback shift register of a code generator to a new state which is at a known offset from a current state.