Enciphering system applicable to various keyless entry systems

Abstract

An enciphering system comprises a transmitter (1) and a receiver (2) communicatable with each other and incorporated in a keyless entry system. The transmitter (1) comprises a memory (11) for memorizing an ID code, a first micro processor (12) for enciphering the ID code outputted from the memory (11), and a transmitting section (13) for transmitting an enciphered ID code produced by the first micro processor (12). The receiver (2) comprises a receiving section (22) for receiving the enciphered ID code transmitted from the transmitter (1) and a second micro processor (21) for decoding the enciphered ID code. The first micro processor (12) divides both the ID code and an associated rolling code into a plurality of blocks, the rolling code varying its content in response to each transmission of the ID code through the transmitting section (13), determines a repetition number for an enciphering arithmetic operation in a process of the arithmetic operation, and repeats the enciphering arithmetic operation in each block according to the repetition number, thereby enciphering the ID code. The second micro processor (21) decodes the enciphered ID code by reversely performing the operation of the first micro processor (12).