factor: trim using lists

[factor.git] / extra / random / blum-blum-shub / blum-blum-shub.factor

diff --git a/extra/random/blum-blum-shub/blum-blum-shub.factor b/extra/random/blum-blum-shub/blum-blum-shub.factor
old mode 100755 (executable)
new mode 100644 (file)
index 017ef40..b86acd7
--- a/extra/random/blum-blum-shub/blum-blum-shub.factor
+++ b/extra/random/blum-blum-shub/blum-blum-shub.factor
@@ -1,36 +1,29 @@
-USING: kernel math sequences namespaces
-math.miller-rabin combinators.lib
-math.functions accessors random ;
+USING: accessors kernel math math.functions math.primes random ;
 IN: random.blum-blum-shub
 
-! TODO: take (log log M) bits instead of 1 bit
-! Blum Blum Shub, M = pq
+! 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 ;
 
-C: <blum-blum-shub> blum-blum-shub
+<PRIVATE
+
+: generate-bbs-prime ( numbits -- p )
+    dup random-prime dup 4 mod 3 =
+    [ nip ] [ drop generate-bbs-prime ] if ;
 
 : generate-bbs-primes ( numbits -- p q )
-    #! two primes congruent to 3 (mod 4)
-    [ [ random-prime ] curry [ 4 mod 3 = ] generate ] dup bi ;
+    [ generate-bbs-prime ] [ generate-bbs-prime ] bi ;
+
+: next-bbs-bit ( bbs -- bit )
+    dup [ x>> 2 ] [ n>> ] bi ^mod [ >>x drop ] [ 1 bitand ] bi ;
+
+PRIVATE>
 
-IN: crypto
 : <blum-blum-shub> ( numbits -- blum-blum-shub )
-    #! returns a Blum-Blum-Shub tuple
     generate-bbs-primes *
     [ find-relative-prime ] keep
-    blum-blum-shub construct-boa ;
-
-! 256 make-bbs blum-blum-shub set-global
-
-: next-bbs-bit ( bbs -- bit )
-    #! x = x^2 mod n, return low bit of calculated x
-    [ [ x>> 2 ] [ n>> ] bi ^mod ]
-    [ [ >>x ] keep x>> 1 bitand ] bi ;
-
-IN: crypto
-! : random ( n -- n )
-    ! ! #! Cryptographically secure random number using Blum-Blum-Shub 256
-    ! [ log2 1+ random-bits ] keep dupd >= [ -1 shift ] when ;
+    blum-blum-shub boa ;
 
-M: blum-blum-shub random-32* ( bbs -- r )
-    ;
+M: blum-blum-shub random-32*
+    0 32 rot
+    [ next-bbs-bit swap 1 shift bitor ] curry times ;