Does setting Aes KeySize generate a new key?

Question

According to Microsoft's documentation on System.Security.Cryptography.Aes, the key size can simply be changed by setting the KeySize property.

Does changing the key size automatically generate a new random key of the new key size? The documentation is not clear.

Answer 1

Yes, or no, depending.

Setting KeySize makes the object forget the key. If a new one is provided by setting Key no new key was technically generated. But when the object has no key, but needs one, a new key (of size KeySize) is created and remembered.

In general, you should either set KeySize (to make a random one) or Key (which adjusts KeySizeValue), not both.