subject text <i> Blum Blum Shub (BBS) is a pseudorandom number generator proposed in 1986 by Lenore Blum, Manuel Blum and Michael Shub... <p> BBS takes the form: <pre> x <- mod(pow(x, 2), M) </pre> [where M is the product of two large primes and the output is the bit parity of x] <p> The generator is not appropriate for use in simulations, only for cryptography [xoring the pseudo-random sequence of a given seed with the text to encrypt it], because it is not very fast. However, it has an unusually strong security proof, which relates the quality of the generator to the computational difficulty of integer factorization... <p> If integer factorization is difficult (as is suspected) then BBS with large M will have an output free from any nonrandom patterns that can be discovered with any reasonable amount of calculation. This makes it as secure as other encryption technologies tied to the factorization problem, such as RSA encryption. </i> <p> <a href=http://en.wikipedia.org/wiki/Blum_Blum_Shub>Wikipedia entry</a><br> <a href=http://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator>Cryptographically secure pseudorandom number generator</a><br> <a href=http://perltraining.com.au/~jarich/Primes/index.html>Generating Large Primes (with source code)</a> password