diff options
| -rw-r--r-- | challenge/c21.go | 16 | ||||
| -rw-r--r-- | cryptopals.go | 2 | ||||
| -rw-r--r-- | lib/rng.go | 69 |
3 files changed, 87 insertions, 0 deletions
diff --git a/challenge/c21.go b/challenge/c21.go new file mode 100644 index 0000000..3cc3dd3 --- /dev/null +++ b/challenge/c21.go @@ -0,0 +1,16 @@ +// Copyright © 2021 rsiddharth <s@ricketyspace.net> +// SPDX-License-Identifier: ISC + +package challenge + +import ( + "fmt" + + "ricketyspace.net/cryptopals/lib" +) + +func C21() { + for { + fmt.Printf("%v\n", lib.MTExtract()) + } +} diff --git a/cryptopals.go b/cryptopals.go index 103bfbb..98b6759 100644 --- a/cryptopals.go +++ b/cryptopals.go @@ -59,5 +59,7 @@ func main() { challenge.C19() case 20: challenge.C20() + case 21: + challenge.C21() } } diff --git a/lib/rng.go b/lib/rng.go new file mode 100644 index 0000000..7e7611e --- /dev/null +++ b/lib/rng.go @@ -0,0 +1,69 @@ +// Copyright © 2021 rsiddharth <s@ricketyspace.net> +// SPDX-License-Identifier: ISC + +package lib + +// MT19937 coefficients. +var mtCoefW uint32 = 32 +var mtCoefN uint32 = 624 +var mtCoefM uint32 = 397 +var mtCoefR uint32 = 31 +var mtCoefA uint32 = 0x9908B0DF +var mtCoefU uint32 = 11 +var mtCoefD uint32 = 0xFFFFFFFF +var mtCoefS uint32 = 7 +var mtCoefB uint32 = 0x9D2C5680 +var mtCoefT uint32 = 15 +var mtCoefC uint32 = 0xEFC60000 +var mtCoefL uint32 = 18 + +var mtF uint32 = 1812433253 + +// Stores state of MT19937 generator. +var mtGenSt []uint32 = make([]uint32, mtCoefN) +var mtIndex uint32 = mtCoefN + 1 + +var mtLowerMask uint32 = (1 << mtCoefR) - 1 +var mtUpperMask uint32 = 0xFFFFFFFF & (^mtLowerMask) + +func MTSeed(seed uint32) { + mtIndex = mtCoefN + mtGenSt[0] = seed + for i := uint32(1); i < mtCoefN; i++ { + mtGenSt[i] = (0xFFFFFFFF & + (mtF*(mtGenSt[i-1]^(mtGenSt[i-1]>>(mtCoefW-2))) + i)) + } +} + +func MTExtract() uint32 { + if mtIndex >= mtCoefN { + if mtIndex > mtCoefN { + MTSeed(5489) + } + mtTwist() + } + + y := mtGenSt[mtIndex] + y = y ^ ((y >> mtCoefU) & mtCoefD) + y = y ^ ((y << mtCoefS) & mtCoefB) + y = y ^ ((y << mtCoefT) & mtCoefC) + y = y ^ (y >> mtCoefL) + + mtIndex = mtIndex + 1 + + r := 0xFFFFFFFF & y + return r +} + +func mtTwist() { + for i := uint32(0); i < mtCoefN-1; i++ { + x := (mtGenSt[i] & mtUpperMask) + + (mtGenSt[(i+1)%mtCoefN] & mtLowerMask) + xA := x >> 1 + if x%2 != 0 { // lowest bit of x is 1 + xA = xA ^ mtCoefA + } + mtGenSt[i] = mtGenSt[(i+mtCoefM)%mtCoefN] ^ xA + } + mtIndex = 0 +} |