Question

I have following code written in Java

Mac mac = Mac.getInstance("HmacSHA1");
String secretKey ="sKey";
String content ="Hello";

byte[] secretKeyBArr = secretKey.getBytes();    
byte[] contentBArr = content.getBytes();

SecretKeySpec secret_key = new SecretKeySpec(secretKeyBArr,"HmacSHA1");
byte[] secretKeySpecArr = secret_key.getEncoded();

mac.init(secret_key);

byte[] final = mac.doFinal(contentBArr);

I want to make same example in C#. So, I wrote following code

HMACSHA1 hmacsha1 = new HMACSHA1();
string secretKey = "sKey";
string content = "Hello";

byte[] secretKeyBArr = Encoding.UTF8.GetBytes(secretKey);
byte[] contentBArr = Encoding.UTF8.GetBytes(content);

hmacsha1.Key = secretKeyBArr;
byte[] final = hmacsha1.ComputeHash(contentBArr);

Final results are not equal. secretKeyBArr and contentBArr are byte array and their values are same in both example. What is unknown is SecretKeySpec passed to mac.init(). So, what is equivalent same class in C#?

Answer 1

The results are identical, but Java uses signed bytes while C# uses unsigned bytes by default.

Furthermore, SecretKeySpec itself normally does not change the underlying data. You need to e.g. put a DES key specification in a SecretKeyFactory to make sure that the parity bits are set correctly (in the resulting SecretKey). So there is no need for an equivalent as the class itself does very little except wrapping the data.