PHP / Javascript / JQuery - base64 sha256 encoding

Question

I'm trying to port a PHP example of an API integration to Javascript / JQuery. In PHP, an encrypted string is created using the following code:

$sig = base64_encode(hash_hmac('sha256', $sign, $this->secretAccessKey, true)

whose functions are documented here:

http://php.net/manual/en/function.hash-hmac.php

http://us.php.net/base64_encode

In Javascript, I'm using JQuery's crypto to do the HMAC piece:

http://code.google.com/p/crypto-js/#HMAC-SHA256

and I'm trying to figure out if I also need to do a base64 encode, as it seems it is already in base64. This is the code I'm currently running:

var sigHash = Crypto.HMAC(Crypto.SHA256, sign, accessKey);

Is this correct? How would I create a javascript / jquery equivalent of the above PHP function?

Dennis · Accepted Answer · 2012-04-23 16:40:38Z

2

HMAC is a standard. So is SHA-256. So their outputs, regardless of which implementation, has to be the same.

There could only be differences in the Base64 encoding. Normally, the non-alphanumeric characters are + and /, but you cannot count on that. I've checked, and both implementations use the same non-alphanumeric characters.

However, you should still "manually" check a few thousand strings. The implementation in PHP is well tested. But I do not know if the same is true for the implementation in jQuery...

The syntax for Base64 encoded output is:

Crypto.util.bytesToBase64(
    Crypto.HMAC(Crypto.SHA256, sign, accessKey, { asBytes: true })
);

edited Apr 23, 2012 at 16:40

answered Oct 26, 2011 at 21:47

Dennis

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2 Comments

mheavers Over a year ago

Thanks - I think what I need to know though, is it enough just to run the crypto function in javascript to get the equivalent to the PHP functions, or do I need to run the crypto function, and an addition base64_encode function

Dennis Over a year ago

The standard output of the function is hexadecimal encoding, not Base64. For Base64 encoding, see updated answer.

Rob W · Accepted Answer · 2011-10-26 21:49:48Z

1

If you ever need inspiration for a JS implementation of a PHP function, have a look at PHPJS.org. The JavaScript equivalent for base64_encode can be found at: base64_encode.

answered Oct 26, 2011 at 21:49

Rob W

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