perchi

perchi is the implementation of ciphers like Caesar or Vigenère in JavaScript.

Name 'perchi' is anagram: 'perchi' = 'cipher'

Install

$ npm install perchi

Available ciphers

• CaesarCipher
• VigenereCipher
• AtbashCipher
• BaconCipher
• RailFenceCipher
• AffineCipher
• PlayfairCipher
• ColumnarTranspositionCipher

Usage

You can use the perchi byimport-ing the module:

import CaesarCipher from "perchi";

or use require:

const { CaesarCipher } = require("perchi");

It returns collections of utility classes. Each cipher implementation has encrypt and decrypt methods which are synchronous. For large input, use encryptAsync and decryptAsync; they run in a Node.js worker thread and return a Promise. Some of ciphers has implemented breakCipher functions that break the code for example by brute-force atack. By default ciphers implementations use the following alphabet: ABCDEFGHIJKLMNOPQRSTUVWXYZ.

Example of Caesar cipher with left shift of 3:

CaesarCipher.encrypt("perchi is cool", -3);
// mbozef fp zlli

CaesarCipher.decrypt("mbozef fp zlli", -3);
// perchi is cool

Example of Atbash cipher with custom alphabet:

const polishAlphabet = "aąbcćdeęfghijklłmnńoóprsśtuwyzźż";

AtbashCipher.encrypt("Zażółć gęślą jaźń", polishAlphabet);
// Bżaimw rśęnź ożąk

AtbashCipher.decrypt("Bżaimw rśęnź ożąk", polishAlphabet);
// Zażółć gęślą jaźń

Additional ciphers

All ciphers in this package are educational classical ciphers, not secure encryption.

const {
  RailFenceCipher,
  AffineCipher,
  PlayfairCipher,
  ColumnarTranspositionCipher,
} = require("perchi");

RailFenceCipher.encrypt("WEAREDISCOVEREDFLEEATONCE", 3);
// WECRLTEERDSOEEFEAOCAIVDEN

AffineCipher.encrypt("AFFINE CIPHER", 5, 8);
// IHHWVC SWFRCP

PlayfairCipher.encrypt("HIDETHEGOLDINTHETREESTUMP", "PLAYFAIR EXAMPLE");
// BMODZBXDNABEKUDMUIXMMOUVIF

ColumnarTranspositionCipher.encrypt("WEAREDISCOVEREDFLEEATONCE", "ZEBRAS");
// EVLNACDTESEAROFODEECWIREE

RailFenceCipher takes an integer rail count. AffineCipher takes a multiplier that must be coprime with the alphabet length and a shift. ColumnarTranspositionCipher preserves every input character and uses a non-empty key.

PlayfairCipher uses the standard 25-letter alphabet (I and J share a position), converts text to uppercase, ignores unsupported characters, and inserts X filler symbols for repeated or trailing letters. Decryption retains those filler symbols because it cannot reliably distinguish them from real X characters.

Async performance

Run the reproducible benchmark with:

npm run benchmark:async

The asynchronous methods use a Node.js worker thread. This keeps the main event loop available, but a newly created worker has startup and message-transfer overhead. On Node.js v24.16.0, arm64 with 15 logical CPU cores, using a 5 MiB Caesar input and five samples, the median results were:

| Operation | Median time | | --- | ---: | | Synchronous completion | 253.4 ms | | Async dispatch to worker | 0.4 ms | | Async completion | 292.5 ms |

In every sample the event loop completed a setImmediate turn before the asynchronous cipher completed. Use encryptAsync and decryptAsync when main-thread responsiveness matters; use the synchronous methods for small inputs or when lowest completion latency matters.

License

ISC © bypopdev