Bad decrypt on NodeJS Triple DES implementation? - node.js

Question

var cardInfo = "<Card><CVV></CVV><CardNumber></CardNumber><ExpMonth></ExpMonth><ExpYear></ExpYear><Member></Member></Card>"
function genKeyPair(passphrase){
var iv = crypto.createHash('md5').update(passphrase).digest('hex').substring(0, 8)
var key = crypto.createHash('md5').update(passphrase).digest('hex').substring(0, 24)
return {
key: key,
iv: iv
}
}
function encrypt3DES(key, vector, data){
var encryptor = crypto.createCipheriv('des3', key, vector)
var raw = new Buffer(data)
encryptor.update(raw)
var encrypted = encryptor.final()
return encrypted
}
function decrypt3DES(key, vector, data){
var decryptor = crypto.createDecipheriv('des3', key, vector)
decryptor.update(data)
var decrypted = decryptor.final()
return decrypted
}
var key = genKeyPair('test')
var data3DES = encrypt3DES(key.key, key.iv, cardInfo)
var decryptedCard = decrypt3DES(key.key, key.iv, data3DES)
So, I get a "bad decrypt" on decryptor.final() and can't figure out why.
Node expects a buffer when encrypting so you see I provide that in the beginning of the encrypt3DES
I put the raw buffer output from encryption straight into the decrypt method
What am I doing wrong here?
DISCLAIMER
No, this is not going to be used in production. I'm just toying around so please hold with the "you don't know what you're doing so you shouldn't do it" talk

Answer 1

The results of update are thrown away in your code:
Returns the enciphered contents, and can be called many times with new data as it is streamed.
The code also uses 3DES ABC keys that do not contain enough entropy (keys should be binary data, not hexadecimals). At least try to use crypto.createCipher(algorithm, password) or try and find an implementation of PBKDF2 in JavaScript.

Answer 2

here is algorithm related key and iv lengths relations, as
DES-ECB Key: 8; IV: 0
DES-CBC Key: 8; IV: 8
DES-CFB Key: 8; IV: 8
DES-CFB1 Key: 8; IV: 8
DES-CFB8 Key: 8; IV: 8
DES-EDE-CBC Key: 16; IV: 8
DES-EDE-CFB Key: 16; IV: 8
DES-EDE-OFB Key: 16; IV: 8
DES-EDE3-CBC Key: 24; IV: 8
DESX-CBC Key: 24; IV: 8
and, this is a runnable example
const crypto = require('crypto');
const iv = '12345678';
const key = '123456'.padEnd(24,'0');
const ivHex = Buffer.from(iv, 'utf8');
const keyHex = Buffer.from(key, 'utf8');
const decrypt = (text)=>{
const cipher = crypto.createDecipheriv('DES-EDE3-CBC', keyHex,ivHex);
let c = cipher.update(text, 'base64','utf8')
c += cipher.final('utf8');
return c;
}
const encrypt = (text)=>{
const cipher = crypto.createCipheriv('DES-EDE3-CBC', keyHex,ivHex);
let c = cipher.update(text, 'utf8' ,'base64');
c+=cipher.final('base64');
return c;
}
const text = '7LBIMxZKDB0=';
const plaintext = decrypt(text);
console.log(plaintext);//123456
const cipherText = encrypt(plaintext);
console.log(cipherText, text === cipherText);//7LBIMxZKDB0= true
hope it helps.