# What does this protocol mean?

Does this mean that the message is being added onto the hashed(message, tag) ?

m || H(m, "secret")


So the output would be something like:

"RandomMessage"+N8HqKCG01b

Yes, || means concatenation. If H means HMAC and 'secret' is a secret key then this is secure.
If H is a hash instead of a MAC, then this is insecure.
• @NoDirection if message is transmitted in the clear, there is no confidentiality. If H is a cryptographic hash function, then there is no integrity (you need HMAC for that). – Z.T. Nov 15 '16 at 23:10