CODEWITHSUNDEEP
javajavascriptnode.jsencryptioncryptography
Dmitry Minkovsky
Dmitry Minkovsky

Reputation: 38183

Porting AES Java decipher code to Node.js

I've got the following Java code that I'd like to port to Node.js:

// Java

byte[] rawKey = "deadbeefdeadbeef".getBytes("us-ascii");
SecretKeySpec skeySpec = new SecretKeySpec(rawKey, "AES");
Cipher cip = Cipher.getInstance("AES/ECB/NoPadding");
cip.init(Cipher.DECRYPT_MODE, skeySpec);
byte[] plaintext = cip.doFinal(ciphertext, 0, ciphertext.length);

Here's my attempt with Node.js, using streams

// JS, using the crypto streams API

var decipher = crypto.createDecipher('aes-128-ecb', 'deadbeefdeadbeef');
decipher.setAutoPadding(false);
decipher.pipe(concat(function(plaintext) { console.log(plaintext); });
decipher.end(ciphertext);

And, also a Node.js attempt using the older .update() and .final() API:

// JS, using the `.update()` and `.final()` API

var decipher = crypto.createDecipher('aes-128-ecb', 'deadbeefdeadbeef');
decipher.setAutoPadding(false);
var pieces = [];
pieces.push(new Buffer(decipher.update(ciphertext)));
pieces.push(new Buffer(decipher.final()));
var plaintext = Buffer.concat(pieces);

Both of these versions produce the same output of the correct length (the same length as the input), but this output is not the same plaintext that is produced by the Java version of the decipher operating on the same input buffer. How can I set up a Node.js decipher like the Java decipher configured above?

Thank you.

Upvotes: 4

Views: 1073

Answers (1)

Maarten Bodewes
Maarten Bodewes

Reputation: 94058

createDecipher actually does not use a key as you do in Java. It uses a password, which is fed into a Password Based Key Derivation Function (PBKDF) to derive the key. Hence with a different key and no method of checking the correctness of the key, you will get random plain text.

The Node.js API is not very well named, the functions createDecipher and createDecipheriv suggest that the latter is just the same as the former, with the addition of an IV. Instead, createDecipher adds an entire key derivation function to the mix.

Upvotes: 4

Related Questions