I'm aware that it's crucial to include the IV when calculating the HMAC of a ciphertext (assuming an IV is used). Can anyone explain, in simple terms, why this is?
Furthermore, assume that there is other metadata associated with the cipher, which needs to be known to correctly decrypt the ciphertext (for example, the type of algorithm used, the mode, options such as configurable block size, etc). Is there any sense in including this information when calculating the HMAC? Or on the contrary, is the any reason not to?