rudal-cipher-toolkit/index.js

A package for encrypting and decrypting messages using a Vigenère cipher variant.

let space = [];
function encode_message({message, secretKey}) {
  if (typeof message !== 'string' || typeof secretKey !== 'string') {
    throw new Error ('Both message and secretKey should be strings.');
  }
  for (let i = 0; i < message.length; i++) {
    if (message[i].match (' ')) {
      space.push (i);
    }
  }

  let msgArray = message.split (' ');

  let msgCodeArray = toCodeArray (msgArray);
  let keyCodeArray = toCodeArray (secretKey);

  let encodedCodeArray = toEncodedMessageArray (msgCodeArray, keyCodeArray);
  let encodedMsgArray = toCharArray (encodedCodeArray, space);

  return encodedMsgArray.join ('');
}

function toCodeArray (arr) {
  let newArray = [];
  let m = arr.toString ();
  for (let i = 0; i < m.length; i++) {
    if (m[i].match (' ') || m[i].match (',')) {
      continue;
    } else {
      let code = toCode (m[i]);
      newArray.push (code);
    }
  }
  return newArray;
}

function toCode (l) {
  return l.charCodeAt (0) - 96;
}

function toEncodedMessageArray (arr, keyCode) {
  let newArray = [];
  let j = 0;
  for (let i = 0; i < arr.length; i++) {
    if (j > keyCode.length - 1) {
      j = 0;
    }
    let tempKeyCode = keyCode[j];
    let tempMessageCode = arr[i];

    let code = tempMessageCode + tempKeyCode;

    if (code > 26) {
      newArray.push (code - 26 + 96);
    } else {
      newArray.push (code + 96);
    }
    j++;
  }
  return newArray;
}

function toCharArray (arr) {
  let newArray = [];
  let counter = 0;
  for (let i = 0; i < arr.length; i++) {
    for (let j = 0; j < space.length - 1; j++) {
      if (i + counter === space[j]) {
        newArray.push (' ');
        counter++;
        break;
      }
    }
    newArray.push (String.fromCharCode (arr[i]));
  }

  return newArray;
}

function decode_message({message, secretKey}) {
  if (typeof message !== 'string' || typeof secretKey !== 'string') {
    throw new Error ('Both message and secretKey should be strings.');
  }

  let msgArray = message.split (' ');

  let msgCodeArray = toCodeArray (msgArray);
  let keyCodeArray = toCodeArray (secretKey);

  let decodedCodeArray = toDecodedMessageArray (msgCodeArray, keyCodeArray);
  let decodedMsgArray = toCharArray (decodedCodeArray);

  return decodedMsgArray.join ('');
}

function toDecodedMessageArray (arr, keyCode) {
  let newArray = [];
  let j = 0;
  for (let i = 0; i < arr.length; i++) {
    if (j > keyCode.length - 1) {
      j = 0;
    }
    let tempKeyCode = keyCode[j];
    let tempMessageCode = arr[i];

    let code = tempMessageCode - tempKeyCode;
    if (code <= 0) {
      newArray.push (code + 26 + 96);
    } else {
      newArray.push (code + 96);
    }
    j++;
  }
  return newArray;
}

module.exports = {
  encode_message,
  decode_message,
};