Previously an incorrectly sized key was either silently padded
with NUL bytes or truncated. Especially the silent nature of this
behavior makes it extremely easy to use weak encryption. A common
mistake - which has also been extensively made in our tests - is
to use a password instead of a key.
Incorrectly sized keys will now be rejected.
Previously, if the size of the IV did not match the block size
mcrypt would throw a warning and fall back to a NUL IV. This
behavior is both dangerous and makes no practical sense.
mcrypt_encrypt etc. will now return false if the IV has an incorrect
size.
