HMACSHA256 output bytes / bits

Question

My Friend told me to use "HMACSHA256" algo and i have used the below code :

SecretKey signingKey = new SecretKeySpec("123".getBytes(), "HMACSHA256");  
    Mac mac = Mac.getInstance("HMACSHA256");  
    mac.init(signingKey);  
    byte[] digest = mac.doFinal("ABCDEF".getBytes());     
    System.out.println("HMA : "+digest.length);

Just wanted to know that :

1) is the above implementation looks standard "HMACSHA256" ?

2) Output (digest) is coming as 256 bits or 16 bytes.Is this correct.

If we are using HMACSHA256 algo, how many bytes we need to expect to come as an output.

Perception · Accepted Answer · 2012-02-16 13:00:52Z

11

The number of output bits for HMAC digests is equal to the bits generated by the underlying algorithm.

For MD5 this number of bits is 128.
For SHA-1 this number of bits is 160.
For SHA-256 this number of bits if 256.

Your code looks fine and is generating the correct digest size. You can read more on cryptographic hashes here.

answered Feb 16, 2012 at 13:00

Perception

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1 Comment

AdrianRM Over a year ago

Quick translation to bytes: For MD5 this number of bytes is 16. For SHA-1 this number of bytes is 20. For SHA-256 this number of bytes is 32.

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