Node.js Crypto input/output types

Question

I am trying to figure out the Node.js Crypto library and how to use it properly for my situation.

My Goal is:

key in hex string 3132333435363738313233343536373831323334353637383132333435363738

text in hex string 46303030303030303030303030303030

ciphered text in hex string 70ab7387a6a94098510bf0a6d972aabe

I am testing this through ac implementation of AES 256 and through a website at http://www.hanewin.net/encrypt/aes/aes-test.htm

This is what I have to far, it's not working the way I would expect it to work. My best guess is that the input and output types are incorrect for the cipher function. The only one that works is utf8 if I use hex it fails with a v8 error. Any ideas on what I should convert or change to get it to work.

var keytext = "3132333435363738313233343536373831323334353637383132333435363738";
var key = new Buffer(keytext, 'hex');
var crypto = require("crypto")
var cipher = crypto.createCipher('aes-256-cbc',key,'hex');
var decipher = crypto.createDecipher('aes-256-cbc',key,'hex');

var text = "46303030303030303030303030303030";
var buff = new Buffer(text, 'hex');
console.log(buff)
var crypted = cipher.update(buff,'hex','hex')

The output in crypted in this example is 8cfdcda0a4ea07795945541e4d8c7e35 which is not what I would expect.

Answer 1

Your code is using aes-256-cbc when the website you are deriving test vectors from is using ecb mode. Also, you are calling createCipher , but with ECB you should use createCipheriv with no IV (see nodeJS: can't get crypto module to give me the right AES cipher outcome ),

Here is some code that demonstrates this:

var crypto = require("crypto");

var testVector = { plaintext : "46303030303030303030303030303030",
    iv : "",
    key : "3132333435363738313233343536373831323334353637383132333435363738",
    ciphertext : "70ab7387a6a94098510bf0a6d972aabe"};

var key = new Buffer(testVector.key, "hex");
var text = new Buffer(testVector.plaintext, "hex");
var cipher = crypto.createCipheriv("aes-256-ecb", key, testVector.iv);
var crypted = cipher.update(text,'hex','hex');
crypted += cipher.final("hex");
console.log("> " + crypted);
console.log("? " + testVector.ciphertext);

The output of running that code is not exactly what I expect, but the first block of the encrypted output matches your expectation. Probably another parameter that needs to be tweaked.:

$ node test-aes-ecb.js 
> 70ab7387a6a94098510bf0a6d972aabeeebbdaed7324ec4bc70d1c0343337233
? 70ab7387a6a94098510bf0a6d972aabe