I was reading about Encrypt-then-MAC and everywhere I go it seems people include the IV with the ciphertext generated for each message then MAC that and send all the information concatenated.
Why do I need to send the IV more than once?
I was reading about Encrypt-then-MAC and everywhere I go it seems people include the IV with the ciphertext generated for each message then MAC that and send all the information concatenated.
Why do I need to send the IV more than once?
I assume your protocol is message oriented. You needn't repeat the IV, but need to supply a new one for every message.
This can be either:
For CBC mode, the IVs should be sufficiently random, e.g. output from (2) may be hashed.