93 lines
2.9 KiB
TypeScript
93 lines
2.9 KiB
TypeScript
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import { range, englishFreqs } from './utils';
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type HexToBuff = (hex: string) => Buffer;
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export const hexToBuff: HexToBuff = (hex) => Buffer.from(hex, 'hex');
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type BuffTo64 = (buff: Buffer) => string;
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export const buffTo64: BuffTo64 = (buff) => buff.toString('base64');
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type XorBuffers = (buff1: Buffer, buff2: Buffer) => Buffer;
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export const xorBuffers: XorBuffers = (buff1, buff2) => {
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const resBuff = Buffer.alloc(buff1.length);
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range(0, buff1.length).forEach(i => {
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resBuff[i] = buff1[i] ^ buff2[i];
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});
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return resBuff;
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};
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type EncryptSingleByte = (msg: Buffer, key: number) => Buffer;
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export const encryptSingleByte: EncryptSingleByte = (msg, key) => {
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const resBuffer = Buffer.alloc(msg.length);
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range(0, msg.length).forEach(i => {
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resBuffer[i] = msg[i] ^ key;
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});
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return resBuffer;
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};
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type DecryptSingleByte = (msg: Buffer, key: number) => Buffer;
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export const decryptSingleByte: DecryptSingleByte = (msg, key) => {
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const resBuffer = Buffer.alloc(msg.length);
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range(0, msg.length).forEach(i => {
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resBuffer[i] = msg[i] ^ key;
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});
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return resBuffer;
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};
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type EnglishByteFreqs = () => { [id: number]: number };
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const englishByteFreqs: EnglishByteFreqs = () => {
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const byteFreqs = {} as { [id: number]: number };
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range(0, 255).forEach(i => byteFreqs[i] = 0);
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Object.keys(englishFreqs).forEach(k => byteFreqs[k] = englishFreqs[k]);
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return byteFreqs;
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};
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type ByteFreqs = (buff: Buffer) => { [id: number]: number };
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const byteFreqs: ByteFreqs = (buff) => {
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const freqs = {} as { [id: number]: number };
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let n = 0;
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range(0, 255).forEach(i => freqs[i] = 0);
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buff.forEach(b => {
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freqs[b]++;
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n++;
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});
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Object.keys(freqs).forEach(b => freqs[b] = freqs[b] / n);
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return freqs;
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};
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type ScoreBuffer = (buff: Buffer) => number;
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export const scoreBuffer: ScoreBuffer = (buff) => {
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const msgLower = Buffer.from(buff.toString('utf-8').toLowerCase(), 'utf-8');
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const engBFreqs = englishByteFreqs();
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const msgFreq = byteFreqs(msgLower);
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let [cosSimilarity, normMsgFreq, normEngFreq] = [0, 0, 0];
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range(0, 255).forEach(i => {
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cosSimilarity += msgFreq[i] * engBFreqs[i];
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normMsgFreq += msgFreq[i] ** 2;
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normEngFreq += engBFreqs[i] ** 2;
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});
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normMsgFreq = Math.sqrt(normMsgFreq);
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normEngFreq = Math.sqrt(normEngFreq);
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cosSimilarity /= normMsgFreq * normEngFreq;
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return cosSimilarity;
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};
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type CrackSingleByteKeyMsg = (msg: string) => string;
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export const crackSingleByteKeyMsg: CrackSingleByteKeyMsg = (msg) => {
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const candidates = [] as [number, string][];
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range(0, 255).forEach(i => {
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const decrypted = decryptSingleByte(Buffer.from(msg, 'hex'), i);
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candidates.push([scoreBuffer(decrypted), decrypted.toString('utf-8')]);
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});
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candidates.sort((a, b) => b[0] - a[0]);
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return candidates[0][1];
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};
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