Serpent27 / Evanescence

A classical encryption algorithm I made a while back. The original purpose was to encrypt hand-written messages (pseudo)-securely to send by mail - I didn't have access to a computer for a while but I still wanted to encrypt communications

Evanescence

This algorithm is no better than a toy.

After you encrypt a certain amount of data this algorithm is no better than normal Vigenere (which means bad). Please don't use this algorithm if you want any kind of real security, whatsoever. I can and have broken this algorithm myself.

I say this because I've already seen people cloning this repository in the traffic logs. If you want to check out my real encryption work, try looking at PARSEC and Wyndhim. Although they're also not to be trusted (until they get proper review, assuming that ever happens) they're better examples of what proper cryptography looks like.

Or, you could always download GPG (Windows users might find Gpg4Win useful). Gpg4Win is also easier to use than normal GPG; since it provides a nice GUI for all you graphics-loving softies.

Anyway, enough telling you not to use this algorithm... Let's talk about Evanescence!

Evanescence is a cipher-suite based on a combination of the Vigenere cipher and an Autokey cipher. The Evanescence cipher encryption/decryption tool is written in JavaScript, and the cipher itself is designed to be usable purely by hand.

You can use the tool by visiting cipher.serpentsec.com

• The tool has been tested on the following devices:

  • Google Chrome (version 74.0.3729.131 on Windows 10)
  • Firefox (version 66.0.3 on Windows 10)
  • Safari (on iPhone 6s)
  • Google Chrome (version 74.0.3729.136 on Google Pixel 2 XL)
  • Firefox (version 66.0.5 on Google Pixel 2 XL)
  • Firefox 65.0.1 on Linux 4.19.0 (Parrot OS, based on Debian)
  • Chromium 73.0.3683.75 on Linux 4.19.0 (Parrot OS, based on Debian)

• If the tool doesn't work, try switching browsers. Firefox is recommended, but it should work on any modern web browser, including on phones!

How to encrypt messages:

To encrypt messages by hand, you'll need a shared secret[key] and a personal secret, unique to each recipient. It is encouraged to choose both the secret [key], and the personal secret, as randomly as you (reasonably) can. The personal secret functions as an iv. The personal secret is optional (but recommended), and if not specified defaults to a single letter "A", which functions as not modifying the message (In the Vigenere cipher, an "A" combined with any letter is the same letter).

There are a few things to know before encrypting a message:

• The key should be one or more words. The JavaScript code provided only handles messages written primarily in English, or another language with the English alphabet. Any non-English characters are left as-is after encryption.
  • The key can (and should) be more than 1 English word. They should also have varying lengths, since this will increase the effective length of the key.
  • The key should be changed with each message.
• The personal secret should also be more than 1 word. Longer keys = better. The personal secret should be unique to each recipient. For example, Alice would give Bob a different personal secret than she gives to Charlie.

A step-by-step guide to encryption/decryption is available within the app

• Try encrypting and decrypting yourself to see if you're doing it right. You can also use the JavaScript encryption/decryption tool to test your skills with other messages. Once you get the hang of it, it should be fairly easy!
• Make sure to practice both encrypting and decrypting messages.
• If you can read JavaScript, the encryption code can be found in the evanescence_encrypt(...) and evanescence_decrypt(...) functions, when you download the tool.