Maximum security strength in bits of ISAAC cipher?
ISAAC's internal state is a 256-element array of 32-bit words, so the maximum key size is 8192 bits. In theory, this means ISAAC has a maximum keyspace of 28192. It's important to remember, though, that attacks are known that can result from weak states, meaning not all keys are created equal. While this may not be an issue in practice, there are two primary reasons why you shouldn't use it:

It's not particularly well-researched, so more serious attacks may be lurking.

The entire 8192-bit keyspace is utterly unnecessary. 256 is more than enough.


Just stick with 256-bit AES if you need a block cipher, and ChaCha20 if you need a stream cipher.