How do I encrypt a string and get a equal length encrypted string?

Question

My problem is the following:

In an existing database I want to encrypt data in a couple of columns. The columns contains strings of different lengths.

I don\

Answer 1

Ideally, if the existing columns are larger than a single block in a standard block cipher (16 bytes for AES, 8 bytes for TDES), then you could encrypt in CTS (cipher text stealing) mode. Unfortunately, .net does not support CTS in any of its included algorithms. :-(

Normally CTS uses a random IV that would have to be stored along with the ciphertext, but you can just use the row ID or even a constant value if you don't mind identical plaintext values encrypting to identical ciphertext.