From Should we MAC-then-encrypt or encrypt-then-MAC?, I understand I should do Encrypt-than-MAC, which the MAC included all the information such as IV and cipher text.
After reading Why choose an authenticated encryption mode instead of a separate MAC?, I know reusing key in Encryption and MAC may trigger unwanted weaknesses. So I got a question, if the language I used don't have authenticated encryption supported, how should I insert a MAC? The author of the answer suggest to use KDF to solve the problem, but KDF need a salt otherwise it won't work. If I place the salt like
salt||hmac||IV||ciphertext, since the
salt is not protected form the MAC, will it be meaningless to use EtM and/or trigger another weakness?
Articles I have read also: