Dr. Stephen Henson <steve <at> openssl.org> writes:

> 
> On Thu, Jun 14, 2012, Cassie Helms wrote:
> 
> > Hi there!
> > Is there anyone with knowledge about documentation of CMAC functions in 
> > FIPS 
2.0 
> > who can answer this question (CMAC documentation/API similar to HMAC slated 
for 
> > 1.0.1 & FIPS 2.0? 5/23)? Would it be better if I asked the user mailing 
> > list?
> > 
> 
> There isn't any documentation yet, but as you note its usage is almost
> identical to HMAC. The only difference is that you have a symmetric cipher
> instead of a message digest algorithm.
> 
> Steve.
> --
> Dr Stephen N. Henson. OpenSSL project core developer.
> Commercial tech support now available see: http://www.openssl.org
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> 

Dr. Henson, thank you for the quick response. One more brief question for you:

HMAC has a nice wrapper function -- unsigned char *HMAC(lots of args) -- that 
looks like it calls:

HMAC_CTX_init
checks HMAC_Update for error
checks HMAC_Final for error
HMAC_CTX_cleanup

CMAC doesn't have a similar wrapper function at this time.  I am guessing that 
the correct order of CMAC functions (without delving deep into how the 
algorithm 
works) would be to call comparable CMAC functions, like so --

CMAC_Init
check CMAC_Update for error
check CMAC_Final for error
CMAC_CTX_cleanup

Does this look correct? I apologize for the tedious question, but as there is 
no 
documentation or nice wrapper, I would have to investigate the code more to be 
sure...

Thank you.

Cassie



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