0
votes
1answer
39 views

What is the exact purpose of length padding in Merkle–Damgård hash functions? [duplicate]

Is a length padding technique in a hash function used to avoid length extension attacks ?
0
votes
0answers
74 views

Why is Merkle-Damgård construction insecure? [duplicate]

I've been reading about SHA-1. I read that SHA-1 is insecure as it uses the Merkle-Damgård construction and the Merkle-Damgård construction is — according to Wikipedia — susceptible to a variety of ...
4
votes
1answer
296 views

Why is H(message||secret_key) not vulnerable to length-extension attack?

Given a Merkle-Damgård hash function $H$, I know that an attacker can forge a message protected by a MAC computed as $H(\textrm{secret_key}||\textrm{message})$. Why can't he perform the same ...