| 摘要 |
A method and an apparatus for generating encryption stream ciphers are based on a recurrence relation designed to operate over finite fields larger than GF(2). A non-linear output can be obtained by using one or a combination of non-linear processes to form an output function. The recurrence relation and the output function can be selected to have distinct pair distances such that, as the shift register is shifted, no identical pair of elements of the shift register are used twice in either the recurrence relation or the output function. Under these conditions, the recurrence relation and the output function also can be chosen to optimize cryptographic security or computational efficiency. Moreover, it is another object of the present invention to provide a method of assuring that the delay that results for the encryption process does not exceed predetermined bounds. To this end the ciphering delay is measured and if the estimated delay exceeds a predetermined threshold a second ciphering method is employed to limit the accumulated delay of the ciphering operation. |
