factor/extra/random/blum-blum-shub/blum-blum-shub.factor

28 lines
700 B
Factor
Executable File

USING: kernel math sequences namespaces
math.miller-rabin combinators.lib
math.functions accessors random ;
IN: random.blum-blum-shub
! Blum Blum Shub, n = pq, x_i+1 = x_i ^ 2 mod n
! return low bit of x+1
TUPLE: blum-blum-shub x n ;
<PRIVATE
: generate-bbs-primes ( numbits -- p q )
[ [ random-prime ] curry [ 4 mod 3 = ] generate ] dup bi ;
: next-bbs-bit ( bbs -- bit )
dup [ x>> 2 ] [ n>> ] bi ^mod [ >>x drop ] [ 1 bitand ] bi ;
PRIVATE>
: <blum-blum-shub> ( numbits -- blum-blum-shub )
generate-bbs-primes *
[ find-relative-prime ] keep
blum-blum-shub boa ;
M: blum-blum-shub random-32* ( bbs -- r )
0 32 rot
[ next-bbs-bit swap 1 shift bitor ] curry times ;