# Thread: BlumBlumShub

1. ## BlumBlumShub

Description:
[color:#666666]Blum Blum Shub (B.B.S.) is a pseudorandom number generator proposed in 1986 by Lenore Blum, Manuel Blum and Michael Shub (Blum et al., 1986).
More on: Wikipedia

A pseudorandom number generator is an algorithm for generating a sequence of numbers that approximates the properties of random numbers.

prime1 and prime2 are two prime numbers which should be both congruent to 3 modulo 4.

In our case this means that prime1-3 sould be divisible by 4, and (47-3)/4 = 11 so it’s divisible, and prime2-3 should be divisible by 4, and (67-3)/4 = 16 so it’s divisible.

This means The two primes, p and q, should both be congruent to 3 (mod 4) (this guarantees that each quadratic residue has one square root which is also a quadratic residue) and gcd(?(p-1), ?(q-1)) should be small (this makes the cycle length large).

Also, the greatest common divisor of prime1-1 and prime2-1 should be a small number, and that is since the greatest common divisor of 46 and 66 is 2.

xi, also called “seed”, should be an integer different than 1.[/color]

Example:
Show Example

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