Protect/Encrypt Initialization Vector

Is it necessary to protect the initiali开发者_StackOverflow中文版zation vector of AES encrypted data or does it increase the security of the encrypted data if it is protected?

With "protected" I mean, that it is treated equaly as the encryption key, e.g. being encrypted with an asymmectric encryption or being only accessible for authorized persons. An example for the opposite would be, that the initialization vector will be saved unencryoted in a database-field besides the encrypted data.

If it is not desired or meaningfull, may it be that it will be necessary with when using other symmetric encryption algorithms?

Sorry if this is a stupid question, I'm new to cryptography. As far as I understand the ressources I have read, IV has not to be protected, it only has to be unique for each message encrypted with the same key. But maybe I have understood something wrong?

IV's must be unique for the key and unpredictable.

So from the IV up until now the attacker must not be able to guess the next IV. An IV must therefore not be secret.

Generaly an encryption system is considered to be "good" if it is very hard to defeat even if everything but the key is known to the attacker.

More secrecy wont harm though, if the system is still usable with it.