crypto-keygen-suite/keyGen/ciphers/substitutionciphergenerator.js

Key generation utilities for cryptographic operations. YES I RENAMED IT. SIX STATE PROTOCOL!!! See its folder for all <3

import yargs from 'yargs';
import { hideBin } from 'yargs/helpers';

const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';

function validateKey(key) {
  const upperKey = key.toUpperCase();
  if (upperKey.length !== 26) return false;
  const uniqueLetters = new Set(upperKey);
  return uniqueLetters.size === 26;
}

function encrypt(text, key) {
  const map = {};
  for (let i = 0; i < 26; i++) {
    map[alphabet[i]] = key[i].toUpperCase();
  }

  return [...text].map(char => {
    const upper = char.toUpperCase();
    if (alphabet.includes(upper)) {
      const sub = map[upper];
      return char === upper ? sub : sub.toLowerCase();
    }
    return char;
  }).join('');
}

function decrypt(text, key) {
  const map = {};
  for (let i = 0; i < 26; i++) {
    map[key[i].toUpperCase()] = alphabet[i];
  }

  return [...text].map(char => {
    const upper = char.toUpperCase();
    if (key.includes(upper)) {
      const sub = map[upper];
      return char === upper ? sub : sub.toLowerCase();
    }
    return char;
  }).join('');
}

yargs(hideBin(process.argv))
  .command('encrypt', 'Encrypt text using substitution cipher', y => {
    y.option('key', {
      alias: 'k',
      describe: '26-letter substitution key',
      demandOption: true,
      type: 'string'
    }).option('text', {
      alias: 't',
      describe: 'Plaintext to encrypt',
      demandOption: true,
      type: 'string'
    });
  }, argv => {
    const key = argv.key.toUpperCase();
    if (!validateKey(key)) {
      console.error('Invalid key. Key must be a 26-letter permutation of the alphabet.');
      return;
    }
    console.log('Encrypted:', encrypt(argv.text, key));
  })
  .command('decrypt', 'Decrypt text using substitution cipher', y => {
    y.option('key', {
      alias: 'k',
      describe: '26-letter substitution key',
      demandOption: true,
      type: 'string'
    }).option('text', {
      alias: 't',
      describe: 'Ciphertext to decrypt',
      demandOption: true,
      type: 'string'
    });
  }, argv => {
    const key = argv.key.toUpperCase();
    if (!validateKey(key)) {
      console.error('Invalid key. Key must be a 26-letter permutation of the alphabet.');
      return;
    }
    console.log('Decrypted:', decrypt(argv.text, key));
  })
  .demandCommand()
  .strict()
  .help()
  .argv;