I'm working on a system that requires a database and we
would like to encrypt the data in certain table fields.

Lets say it is name information (which it isn't really
nor is it credit card info so arguments about how credit cards
should really be treated/stored/not-stored aren't useful.)
Names are variable length but up to some maximum so if you
were to store them plaintext you might make field name VARCHAR(32).

I have a few questions:

1) block encryption produces ciphertext that is possibly longer
   than the plaintext. I'm using mcrypt and I don't know which
   encryption algorithm I am going to use yet. Is it possible
   to predict what the maximum length of the ciphertext will be?
   I need to know this so that I can pick a larger VARCHAR(???)
   that is capable of holding the ciphertext that results from
   the block encryption of the plaintext (that is at most 32 characters)
   I would rather be precise and not waste space with something like

2) If it is predictable could somebody elaborate on the function
   used to predict the cipher length given a plaintext length of "n"?
   f(n) == ?
   feel free to insert other useful variables such as key length or

3) If my plaintext is not an even block size in length I assume
   the ciphertext will have appended padding data to fill the blocks it
   needs. When I decrypt such a cipher text do I get back my
   exact plaintext or do I get back plaintext plus the padding that
   was used?

Thank you,

Jeff Wiegley

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