Re: Minimum length of secret key

On Sat, 24 Jul 2004, Roger Moser wrote:
>
> SRS uses HMAC-SHA1 where the key is limited to 64 bits. What was the reason
> to use HMAC-SHA1 instead of  SHA-1 applied to the concatenation of a secret
> key (without length limit) and the string to hash?

The reason for using HMAC rather than simply using a cryptographic hash of
the message and a key to form a MAC is that HMAC is more resistant to
attacks that involve replay of the original data concatenated with data
from the attacker.

Tony.
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