AES Encryption - Encrypted value lengths

Question

HI all -
I am attempting to use CF 8's AES encryption feature, and
have not found a critical piece of info in the docs to enable me to
progress.
I am using the function to encrypt a password that can be
from 6 to 16 characters long, which will be stored in a database. I
am using generateSecretKey("AES"), and that gives me a 24 character
key that I'm storing for future decryption use. I find that when I
use the key to encrypt a 6 character password the resulting
encrypted string is 32 characters long, but when I encrypt a 16
character password I get a 64 character encrypted string. This is
the case whether I specify "HEX" or "UU" as the encoding.
Without knowing how the length of the resulting encoded
string is determined, I cannot know how large to make my database
column. (MySQL's AES encryption gives the formula 16 ×
(trunc(string_length / 16) + 1) to arrive at the resulting string's
length, but that formula doesn't yield the results I'm seeing in
CFMX). Can anyone point me to a doc, or explain to me how to
determine the column length for storing the resulting encrypted
value?

Answer 1

No. Only things like key, encoding and string size should
matter. If the encoding is "hex", 1-15 characters should produce
size 32, 16-31 characters should produce 64, etcetera. Unless space
is at a premium, you could always increase the field size if that
makes you feel more comfortable.
Well, the results are dictated by the AES standard and basic
string encoding rules, not CF. I highly doubt either one is going
to change any time soon ;-) I agree documentation is good. However,
unlike aes_encrypt, the encrypt function supports many different
algorithms. Most of which have a distinct set of rules. So it would
probably be difficult to provide accurate information about all of
them. Especially as the specifications for each one alone probably
spans volumes ;-)