From 43de355db213316608a9c1bd914a23a34c98af5f Mon Sep 17 00:00:00 2001 From: rsiddharth Date: Sun, 6 Sep 2020 22:39:30 -0400 Subject: challenge: do challenge 6 * challenge/c06.go: Implement challenge 6. --- challenge/c06.go | 122 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 122 insertions(+) create mode 100644 challenge/c06.go (limited to 'challenge/c06.go') diff --git a/challenge/c06.go b/challenge/c06.go new file mode 100644 index 0000000..6bd7faf --- /dev/null +++ b/challenge/c06.go @@ -0,0 +1,122 @@ +// Copyright © 2020 rsiddharth +// SPDX-License-Identifier: ISC + +package challenge + +import ( + "fmt" + "ricketyspace.net/cryptopals/lib" +) + +var cipher string = `HUIfTQsPAh9PE048GmllH0kcDk4TAQsHThsBFkU2AB4BSWQgVB0dQzNTTmVS +BgBHVBwNRU0HBAxTEjwMHghJGgkRTxRMIRpHKwAFHUdZEQQJAGQmB1MANxYG +DBoXQR0BUlQwXwAgEwoFR08SSAhFTmU+Fgk4RQYFCBpGB08fWXh+amI2DB0P +QQ1IBlUaGwAdQnQEHgFJGgkRAlJ6f0kASDoAGhNJGk9FSA8dDVMEOgFSGQEL 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fmt.Printf("Key is '%s'\n", key) + fmt.Printf("Decrypted text:\n%s", text) +} + +// 'bs' is the data to decrypt. +// 'ks' is the key size. +func crack(bs []byte, ks int) (string, string) { + blocks := lib.BreakIntoBlocks(bs, ks) + blocks = lib.TransposeBlocks(blocks, ks) + + key = "" + for i := 0; i < len(blocks); i++ { + k := findKey(blocks[i]) + + key += string(k) + } + return key, lib.RepeatingXOR(string(bs), key) +} + +func findKey(block []byte) byte { + var k byte + var s int + + s = 0 + for i := byte(0); i < 255; i++ { + ks := lib.FillBytes(i, len(block)) + xs := lib.FixedXORBytes(block, ks) + + score := lib.AlphaPunchScore(xs) + if score > s { + s = score + k = i + } + } + return k +} -- cgit v1.2.3