Encrypt string in java, decrypt in node.js, error: bad decrypt

Question

I'm trying to encrypt a string in java, send it to my node.js server, and decrypt it. However, when I try to do this I get keep getting errors when trying to decrypt.

Java encrypt:

String privateKey = "someprivatekey";
String data = "dataToEncrypt";

DESKeySpec keySpec = new DESKeySpec(privateKey.getBytes("UTF-8"));
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
SecretKey key = keyFactory.generateSecret(keySpec);

byte[] dataToBytes = data.getBytes("UTF-8");      

Cipher cipher = Cipher.getInstance("DES"); 
cipher.init(Cipher.ENCRYPT_MODE, key);

// send this string to server 
String encryptedStr = Base64.encodeToString(cipher.doFinal(dataToBytes), 0);

node.js decrypt:

var privateKey = 'someprivatekey';
var decipher = crypto.createDecipher('des', privateKey);
var dec = decipher.update(textToDecipher, 'base64', 'utf8'); 
dec += decipher.final('utf8'); 
console.log('deciphered: ' + dec);

However, I get this error on the node.js side on the decipher.final() line:

TypeError: error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt

I've tried decoding the string and using a buffer on the node side, but it didn't seem to work either, I get the same bad decrypt error.

var buffer = new Buffer(textToDecipher, 'base64');
var decipher = crypto.createDecipher('des', privateKey);
var dec = Buffer.concat([decipher.update(buffer), decipher.final()]);

Any ideas what I could be doing wrong?

Answer 1

When you create the decipher object on the node server, you are passing a password rather than an actual key. In order to specify the actual key, you need to use crypto.createDecipheriv(), but this requires an actual IV (this example uses 8 null bytes, but that's not recommended for real encryption; Initialization Vector on wikipedia)

I was able to get your example working by explicitly specifying padding, block mode, and IV:

String privateKey = "someprivatekey";
String data = "dataToEncrypt";

DESKeySpec keySpec = new DESKeySpec(privateKey.getBytes("UTF-8"));
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
SecretKey key = keyFactory.generateSecret(keySpec);

byte[] dataToBytes = data.getBytes("UTF-8");      

Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding"); 
cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(new byte[8]));

// send this string to server 
String encryptedStr = Base64.encodeToString(cipher.doFinal(dataToBytes), 0);

The decryption version also explicitly specifies the block mode (des-cbc), and correctly truncates the key text to the first 8 bytes:

var privateKey = 'someprivatekey';
var textToDecipher = '9Y8GTNxhQkKSIm5pmH91VA=='; // Text "dataToEncrypt" encrypted using DES using CBC and PKCS5 padding with the key "someprivatekey"

var iv = new Buffer(8);
iv.fill(0);

var decipher = crypto.createDecipheriv('des-cbc', privateKey.substr(0,8), iv);
var dec = decipher.update(textToDecipher, 'base64', 'utf8');
dec += decipher.final('utf8');
console.log('deciphered: ' + dec);

Answer 2

Java crypto's default mode for DES is ECB, which you need to specify in nodejs:

var decipher = crypto.createDecipheriv('des-ecb', key, new Buffer(0))
var txt = decipher.update(encrypt_text, 'hex', 'utf8');
txt += decipher.final('utf8')
return txt