[cryptography] HMAC over messages digest vs messages

Leandro Meiners lmeiners at gmail.com
Wed Nov 2 15:25:30 EDT 2011

Hi List!

I was wondering if anybody could give me some pointers as to papers or
books that discuss the advantages/disadvantages of computing an HMAC of
a message versus previously computing a hash of the message and then
calculating the HMAC of the hash.
My initial thoughts are that there isn't any additional security
provided by either method.
What about calculating the HMAC of the message concatenated to the hash?
This seems more secure but I have no idea how to prove either statement.
Any helps is greatly appreciated.


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