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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: (302) generating a binary offset number illustrating the offset; (304) generating a counter showing the number of bits in the binary offset number; (306) initializing a temporary state with the unit state; (308) iterating as long as the counter value is higher than zero: (310) multiplying the temporary state by itself by applying a Galois Field multiplication; (312) 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 (314) decrementing the counter value by one; (316) 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.

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First Claim