2
votes
3answers
204 views

How can we sign a contract digitally between two parties?

I'm trying to sign a contract with another party, without using handwritten signatures. I've just read through Applied Cryptography, but there doesn't seem to be a protocol that can solve this ...
7
votes
3answers
308 views

Can one have an authentic, but repudiable, message without a previously shared secret?

Bob wants to send a message to Alice, such that Alice can be sure that the message came from Bob, but can't prove it to anyone else. If I understand right, this means that the same message could have ...
14
votes
1answer
6k views

What are the differences between a digital signature, a MAC and a hash?

A message may be accompanied with a digital signature, a MAC or a message hash, as a proof of some kind. Which assurances does each primitive provide to the recipient? What kind of keys are needed?