cryptol/examples/RC4.cry
2015-01-18 11:47:40 -08:00

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swap : [256][8] -> [8] -> [8] -> [256][8]
swap s i j = [ s @ (if n == i then j else
if n == j then i else
n)
| n <- [0..255]
]
ksa_step : [inf][8] -> [8] -> [8] -> [256][8] -> ([8],[256][8])
ksa_step key i j s = (j', swap s i j')
where j' = j + s@i + key@i
ksa : [inf][8] -> [256][8]
ksa key = (go ! 0).1 where
go : [257]([8],[256][8])
go = [(0,[0..255])] # [ ksa_step key i j s
| i <- [0..255]
| (j,s) <- go
]
ks_step : [8] -> [8] -> [256][8] -> ([8],[256][8],[8])
ks_step i j s = (j',s',s@(s@i + s@j'))
where j' = j + s@i
s' = swap s i j'
ks key = [ k | (_,_,k) <- drop`{1} go ] where
go = [(0,ksa key',0)] # [ ks_step i j s
| i <- loop
| (j,s,k) <- go
]
key' = key # key'
loop = [1..255] # [0] # loop
///////
// "Test vectors" from wikipedia
test1 = take (ks "Key") == [0xEB,0x9F,0x77,0x81,0xB7,0x34,0xCA,0x72,0xA7,0x19]
test2 = take (ks "Wiki") == [0x60,0x44,0xDB,0x6D,0x41,0xB7]
test3 = take (ks "Secret") == [0x04,0xD4,0x6B,0x05,0x3C,0xA8,0x7B,0x59]