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