NIST selects the OMAC as new block cipher mode

[tom st denis]

I'm thinking of adding OMAC to LibTomCrypt however I have a question
not resolved in the paper [or at least I didn't see it].   What is the
standard for computing u^-1 [L * x^-1 specifically] for arbitrary block
sizes?  

I would have simply used a shift code .e.g. 

L2 = L1 xor (L1 << 1) 

Or something like that since it can be computed for any size block
cipher relatively easily.

Tom  

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