# The meaning of formal and semi-formal in cryptography

The question is about "formal" analysis, proofs, etc... What is a correct definition of a formal proof, or a formal analysis? Is there a good way and a bad way to formally prove something. What is the meaning of a a "semi-formal" proof, "semi-formal" argument.

• "Formal" usually means "mathematically correct". – dkaeae Feb 6 '19 at 16:34
• @dkaeae Not really. An informal argument can be perfectly correct, while a completely formal proof can have an error making it incorrect. – Maeher Feb 6 '19 at 19:22
• - A formal proof or derivation is a finite sequence of sentences (called well-formed formulas in the case of a formal language), each of which is an axiom, an assumption, or follows from the preceding sentences in the sequence by a rule of inference (Wiki..) – kelalaka Feb 6 '19 at 21:27