What is the c# equivalent for progressive HMACSHA256?

Question

In Java we have progressive hmac like so:

Mac mac = Mac.getInstance("HmacSHA256");
mac.init(macKey);
mac.update(part(0));
mac.update(part(1));
...
byte[] fullMac = mac.doFinal(part(n))

Please what is the c# equivalent for progressive HMACSHA256?

[`HMACSHA256` class](http://msdn.microsoft.com/en-us/library/system.security.cryptography.hmacsha256.aspx) maybe? — Soner Gönül, Jan 07 '15 at 09:36
@SonerGönül how do we do a progressive hash like you can do with java? — Charles Okwuagwu, Jan 07 '15 at 09:46

score 5 · Accepted Answer · answered Jan 07 '15 at 10:55

Got it! Microsoft over-cooked the otherwise simple Update operation into TransformBlock & TransformFinalBlock

Mac mac = Mac.getInstance("HmacSHA256");
mac.init(macKey);
mac.update(part(0));
mac.update(part(1));
...
byte[] fullMac = mac.doFinal(part(9))

in .Net this now becomes (vb.net)

dim fullMac as byte()
using mac=New HMACSHA256(macKey)
   mac.TransformBlock(part(0),0,part(0).Length,null,0)
   mac.TransformBlock(part(1),0,part(1).Length,null,0)
   ...
   fullMac=mac.TransformFinalBlock(part(9),0,part(9).Length)
end using

I don't see how this helps developer-productivity in any way :(

What is the c# equivalent for progressive HMACSHA256?

1 Answers1