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Diffstat (limited to 'challenge/c19.go')
| -rw-r--r-- | challenge/c19.go | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/challenge/c19.go b/challenge/c19.go new file mode 100644 index 0000000..84ff57b --- /dev/null +++ b/challenge/c19.go @@ -0,0 +1,216 @@ +// Copyright © 2021 rsiddharth <s@ricketyspace.net> +// SPDX-License-Identifier: ISC + +package challenge + +import ( + "fmt" + + "ricketyspace.net/cryptopals/lib" +) + +func C19() { + texts := []string{ + "SSBoYXZlIG1ldCB0aGVtIGF0IGNsb3NlIG9mIGRheQ==", + "Q29taW5nIHdpdGggdml2aWQgZmFjZXM=", + "RnJvbSBjb3VudGVyIG9yIGRlc2sgYW1vbmcgZ3JleQ==", + "RWlnaHRlZW50aC1jZW50dXJ5IGhvdXNlcy4=", + "SSBoYXZlIHBhc3NlZCB3aXRoIGEgbm9kIG9mIHRoZSBoZWFk", + "T3IgcG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==", + "T3IgaGF2ZSBsaW5nZXJlZCBhd2hpbGUgYW5kIHNhaWQ=", + "UG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==", + "QW5kIHRob3VnaHQgYmVmb3JlIEkgaGFkIGRvbmU=", + "T2YgYSBtb2NraW5nIHRhbGUgb3IgYSBnaWJl", + "VG8gcGxlYXNlIGEgY29tcGFuaW9u", + "QXJvdW5kIHRoZSBmaXJlIGF0IHRoZSBjbHViLA==", + "QmVpbmcgY2VydGFpbiB0aGF0IHRoZXkgYW5kIEk=", + "QnV0IGxpdmVkIHdoZXJlIG1vdGxleSBpcyB3b3JuOg==", + "QWxsIGNoYW5nZWQsIGNoYW5nZWQgdXR0ZXJseTo=", + "QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=", + "VGhhdCB3b21hbidzIGRheXMgd2VyZSBzcGVudA==", + "SW4gaWdub3JhbnQgZ29vZCB3aWxsLA==", + "SGVyIG5pZ2h0cyBpbiBhcmd1bWVudA==", + "VW50aWwgaGVyIHZvaWNlIGdyZXcgc2hyaWxsLg==", + "V2hhdCB2b2ljZSBtb3JlIHN3ZWV0IHRoYW4gaGVycw==", + "V2hlbiB5b3VuZyBhbmQgYmVhdXRpZnVsLA==", + "U2hlIHJvZGUgdG8gaGFycmllcnM/", + "VGhpcyBtYW4gaGFkIGtlcHQgYSBzY2hvb2w=", + "QW5kIHJvZGUgb3VyIHdpbmdlZCBob3JzZS4=", + "VGhpcyBvdGhlciBoaXMgaGVscGVyIGFuZCBmcmllbmQ=", + "V2FzIGNvbWluZyBpbnRvIGhpcyBmb3JjZTs=", + "SGUgbWlnaHQgaGF2ZSB3b24gZmFtZSBpbiB0aGUgZW5kLA==", + "U28gc2Vuc2l0aXZlIGhpcyBuYXR1cmUgc2VlbWVkLA==", + "U28gZGFyaW5nIGFuZCBzd2VldCBoaXMgdGhvdWdodC4=", + "VGhpcyBvdGhlciBtYW4gSSBoYWQgZHJlYW1lZA==", + "QSBkcnVua2VuLCB2YWluLWdsb3Jpb3VzIGxvdXQu", + "SGUgaGFkIGRvbmUgbW9zdCBiaXR0ZXIgd3Jvbmc=", + "VG8gc29tZSB3aG8gYXJlIG5lYXIgbXkgaGVhcnQs", + "WWV0IEkgbnVtYmVyIGhpbSBpbiB0aGUgc29uZzs=", + "SGUsIHRvbywgaGFzIHJlc2lnbmVkIGhpcyBwYXJ0", + "SW4gdGhlIGNhc3VhbCBjb21lZHk7", + "SGUsIHRvbywgaGFzIGJlZW4gY2hhbmdlZCBpbiBoaXMgdHVybiw=", + "VHJhbnNmb3JtZWQgdXR0ZXJseTo=", + "QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=", + } + // English alphabets ordered by frequency + // (https://mdickens.me/typing/letter_frequency.html) + ascii := []byte{ + ' ', 'e', 't', 'a', 'o', 'i', 'n', 's', 'r', 'h', 'l', 'd', + 'c', 'u', 'm', 'f', 'g', 'p', 'y', 'w', 'b', ',', '.', + 'v', 'k', '-', '"', '_', '\'', 'x', ')', '(', ';', '0', 'j', + '1', 'q', '=', '2', ':', 'z', '/', '*', '!', '?', '$', '3', + '5', '>', '{', '}', '4', '9', '[', ']', '8', '6', '7', '\\', + '+', '|', '&', '<', '%', '@', '#', '^', '`', '~', + } + // Key: ASCII character; Value: score + asciiScores := make(map[byte]int, 0) + for pos, a := range ascii { + asciiScores[a] = 255 - pos + // Also add the uppercase version of ascii + // character if it exists. + au := lib.ByteToUpper(a) + if a != au { + asciiScores[au] = 255 - pos + } + } + + // Utility functions. + cipherStreamByteGroups := func(ciphers [][]byte) map[int][]byte { + kbg := make(map[int][]byte, 0) + for i := 0; i < len(ciphers); i++ { + for j := 0; j < len(ciphers[i]); j++ { + if _, ok := kbg[j]; !ok { + kbg[j] = make([]byte, 0) + } + kbg[j] = append(kbg[j], ciphers[i][j]) + } + } + return kbg + } + crackOutputBlockByteForGroup := func(pos int, g []byte) byte { + po := make([][]byte, len(g)) // Potential Output block bytes + for i, c := range g { + po[i] = make([]byte, 0) + for _, a := range ascii { + o := c ^ a + po[i] = append(po[i], o) + + // Also try the uppercase version of ascii + // character if it exists. + au := lib.ByteToUpper(a) + if a != au { + o := c ^ au + po[i] = append(po[i], o) + } + } + } + co := lib.BytesInCommon(po) // Common Output Block bytes. + if len(co) < 1 { + return 0 // NUL + } + if len(co) == 1 { + return co[0] + } + tob := byte(0) // The Output Block byte. + bscr := 0 // Best score. + for _, o := range co { + scr := 0 + for _, c := range g { + p := c ^ o + if s, ok := asciiScores[p]; ok { + scr += s + } + if pos == 0 && lib.ByteIsUpper(p) { + scr += 1 + } + } + if scr > bscr { + bscr = scr + tob = o + } + } + return tob + } + + // Make ciphers from plain text data. + ciphers := make([][]byte, len(texts)) + key, err := lib.RandomBytes(16) + if err != nil { + fmt.Printf("Error generating key %v", err) + return + } + nonce := uint64(lib.RandomInt(0, 10)) + for i, b64 := range texts { + text := lib.Base64ToBytes(b64) + ciphers[i], err = lib.AESEncryptCTR(text, key, lib.AESGenCTRFunc(nonce)) + if err != nil { + fmt.Printf("Error encrypting text:%d: %v", i, err) + return + } + } + + // Group the cipher streams into groups by position of the cipher + // byte in the stream. + cbg := cipherStreamByteGroups(ciphers) + + // Try get crack and get the output block stream. + obs := make(map[int]byte, 0) // Output Block Stream map. + for pos, cgrp := range cbg { + obs[pos] = crackOutputBlockByteForGroup(pos, cgrp) + } + + // Decipher cipher using the output block stream. + for _, cipher := range ciphers { + for i, c := range cipher { + p := c ^ obs[i] + fmt.Printf("%c", p) + } + fmt.Printf("\n") + } +} + +// Output: +// I have met them at close of day +// Coming with vivid faces +// From counter or desk among grey +// Eighteenth-century houses. +// I have passed with a nod of the heae +// Or polite meaningless words, +// Or have lingered awhile and said +// Polite meaningless words, +// And thought before I had done +// Of a mocking tale or a gibe +// To please a companion +// Around the fire at the club, +// Being certain that they and I +// But lived where motley is worn: +// All changed, changed utterly: +// A terrible beauty is born. +// That woman's days were spent +// In ignorant good will, +// Her nights in argument +// Until her voice grew shrill. +// What voice more sweet than hers +// When young and beautiful, +// She rode to harriers? +// This man had kept a school +// And rode our winged horse. +// This other his helper and friend +// Was coming into his force; +// He might have won fame in the end, +// So sensitive his nature seemed, +// So daring and sweet his thought. +// This other man I had dreamed +// A drunken, vain-glorious lout. +// He had done most bitter wrong +// To some who are near my heart, +// Yet I number him in the song; +// He, too, has resigned his part +// In the casual comedy; +// He, too, has been changed in his tus +// Transformed utterly: +// A terrible beauty is born. + +// Stuff the program did not get correctly: +// 1. On the 5th line, 'heae' -> 'head' +// 2. On the 38th line, 'tus ' -> 'turn' |