Re: IKEv2 use of HMAC-SHA-1 for Key Derivation

[Hugo Krawczyk <hugo@ee.technion.ac.il>]

Hilarie, can you  clarify what you mean by your comment below?
In particular, what is wrong if K is large and what 
do you mean by "blocksize" in this context?

Thanks,

Hugo

On Tue, 26 Nov 2002, The Purple Streak, Hilarie Orman wrote:

> The HMAC construction is not necessary for key derivation, but both
> methods are wrong if K is large (in size and entropy) and security
> requirements dictate that a derived key must have more entropy than
> 2^(blocksize).  This is a persistently misunderstood issue.
> 
> Hilarie
> 
>