tryte-encrypt

Encrypting tryte strings, such as IOTA seeds.

Installation

npm install tryte-encrypt

Version 2.0

The version 2.0 release is now using the asynchronous scrypt package scrypt-async instead of the former scryptsy.

The tyre-encrypt algorithm has not changed, and it produces the same encryption, and decryption as v1.x.

But the library is now using a callback function, and is not backwards compatibel with synchronous v1.x.

Usage

const crypt = require("./src/tryte-encrypt.js");

let seed = "A9TEST";
let passphrase = "hello"

crypt.encrypt(seed, passphrase, function (encrypted) {
    console.log('Encrypted '+seed+' to '+encrypted);
});

crypt.decrypt(encryptedSeed, passphrase, function (decrypted) {
    console.log('Decrypted '+encryptedSeed+' back to '+decrypted);
});

Example

const crypt = require("./src/tryte-encrypt.js");

let seed = "A9TEST9SEED99RMDKUTQVGFMYPYGAQVOTGJCEFIEELKHRBCZYKAOQQWFRYNGYDAEIKTHQJINZDPYNYOS9";
let passphrase = "Ƥāssφräsę"
console.log('Encrypting:', seed);

crypt.encrypt(seed, passphrase, function (encrypted) {
    console.log('Encrypted:', encrypted, 'using', passphrase);

    console.log('Decrypting...');
    crypt.decrypt(encrypted, passphrase, function (decrypted) {
        if (seed === decrypted) {
            console.log('Decrypted it back to original seed!');
        } else {
            console.log('Decryption failed to get the original seed!');
        }
    });
});

Tuning

By default, the passphrase is hashed using Scrypt with the same arguments as BIP38

const scryptOptionsDefault = 
{
    logN: 14,           // The number of iterations (2^14 = 16384)
    r: 8,               // Memory factor
    p: 8                // Parallelization factor
};

In addition, the option toughness is introduced, where a toughness of 1 is equivalent to {logN: 15, r: 9, p:9}.

crypt.encrypt(seed, passphrase, {logN: 15}, function (encrypted) {...} );
crypt.encrypt(seed, passphrase, {r: 16, p: 2}, function (encrypted) {...} );
crypt.encrypt(seed, passphrase, {p: 2}, function (encrypted) {...} );
crypt.decrypt(encrypted, passphrase, {p: 2}, function (decrypted) {...} );
// Toughness: The two encryptions below will yield the same result
crypt.decrypt(encrypted, passphrase, {toughness: 2}, function (decrypted) {...} );
crypt.decrypt(encrypted, passphrase, {logN: 16, r:10, p:10}, function (decrypted) {...} );

The encrypted seed will by default contain metadata about which scrypt options where used when encrypting. The reasoning is that the security sould lie in the passphrase, and the toughness level, not in remembering wich scrypt parameters you used when encrypting your seed.

The metadata is parsed when decrypting the seed.

Colon is used as a demiliter, since is it not a valid tryte character, but is a valid alphanumeric QR code character. It makes it easy to split the seed from the metadata, both visually and programatically.

Algorithm

The encryption algorithm is based around the BIP38 standard for BitCoin.

Complexity is also a security risk. I've tried to simplify the BIP38 algorithm without losing the security.

This is currently a draft, so feel free to discusse the matter in the issues.

Encryption

The encryption is using AES, SHA256 and Scrypt.

1. The passphrase may be any unicode string, and is encoded to bytes using the UTF-8 encoding.
2. This byte array is double hashed with SHA256
3. Scrypt takes the original passphrase, and the hashed version to create 256 bit encryption key
4. The byte encoded version of the seed, is encrypted with AES, using the CTR mode.

Tryte <-> byte conversion

AES deals only with bytes, not trytes.

Tryte and bytes have different ranges, and one cannot blindly convert from one to the other.

1. The original seed is a text string with tryte3 characters (9 + A-Z).
2. The seed is encoded as bytes using vbakke/trytes.
   (Actually, it is encoded as tryte5 (0-242), which fits inside a byte.)
3. The bytes (tryte5) are encrypted, as above.
4. The encrypted bytes are true bytes using the full range (0-255).
5. The bytes are encoded as tryte6 (0-728), and converted to a tryte string (9 + A-Z).

A seed of 81 tryte3 characters, end up with a string of 100 tryte3 characters.
(Or fifty tryte6 characters, depending of which way you want to look at it.)