How to generate an HMAC in Java equivalent to a Python example?

Question

I'm looking at implementing an app getting Twitter authorization via Oauth in Java. The first step is getting a request token. Here is a Python example for app engine. To test my code, I am running Python and checking output with Java. Here is an example of Python generating a Hash-Based Message Authentication Code (HMAC):

#!/usr/bin/python

from hashlib import sha1
from hmac import new as hmac

key = "qnscAdgRlkIhAUPY44oiexBKtQbGY0orf7OV1I50"
message = "foo"

print "%s" % hmac(key, message, sha1).digest().encode('base64')[:-1]

Output:

$ ./foo.py
+3h2gpjf4xcynjCGU5lbdMBwGOc=

How does one replicate this example in Java?

Here is an HMAC Java example. It uses javax.crypto.Mac, all good. However, the SecretKey constructors take bytes and an algorithm. What's the algorithm in the Python example? How can one create a Java secret key without an algorithm?

Answer 1

HmacSHA1 seems to be what the algorithm name you need:

SecretKeySpec keySpec = new SecretKeySpec(
        "qnscAdgRlkIhAUPY44oiexBKtQbGY0orf7OV1I50".getBytes(),
        "HmacSHA1");

Mac mac = Mac.getInstance("HmacSHA1");
mac.init(keySpec);
byte[] result = mac.doFinal("foo".getBytes());

BASE64Encoder encoder = new BASE64Encoder();
System.out.println(encoder.encode(result));

produces:

+3h2gpjf4xcynjCGU5lbdMBwGOc=

Note that I've used sun.misc.BASE64Encoder for a quick implementation here, but you should probably use something that doesn't depend on the Sun JRE. The base64-encoder in Commons Codec would be a better choice, for example.