cs_protocols_seminary

var - prod by someone else
fresh - prod by us
Bob doesnt know Eve is evil
Eve impersonates Alice and Bob
ni#2 = nonce
<fake sender Eve> Eve is intercepting the msg and resends it to a person
Eve has to change the sender(packet header)
-bob(whoever) starts convers with eve => eve will be able to impersonate him
-eve uses bob as a "decryption machine"
-session keys

EX2
-someone can fake the msg and pretend it's from someone else
-based on the content of the msg you don't know from who the packet is from
Good rules of protocol design
-every msg sh be clear, explicit about sender & receiver
-msg sh have different formats in different formats (else we can take a msg and reuse it in another step)

Ex4
-the purpose: key share (kir) -> A key exchange protocol, key btw i & r
-hash fcts: have to be irevertible, 2 msg sh not have same hash, easy to compute; used to encr passw, sign(compute the hash, sign with the hash); hash -> good for authenticity; to prove that you know a secret
-we dont need nr, we can remove all hashes