I looked at this link that shows how to encrypt a SQL column via a certificate (RSA??) and AES256.
I created a dummy table (script at GitHub) intentionally using identical plain text (Credit Card = 1) and then tries a few simple commands to actually encrypt the data.
I noticed that the resulting cipher text had an identical prefix of bytes. I usually see this in AES ECB but then ECB also results in every block being identical - not just the first. Here the latter portion turns out different despite the same plain test. It might be possible they are using CBC but instead reusing the IV for the entire table?
Edit: The screenshot turned out tiny: Here is the text dump
CardNumber, CardNumber_Encrypted 1, 0x0062513D35F0404A8C2B72A7C64FCDD1010000002887B22A1A1E238BD5658A42F30E0EE34458A4781C4FF7CFAEA91E704E5B9EAE 1, 0x0062513D35F0404A8C2B72A7C64FCDD101000000DFDD0277220EB5CC23D5820FCF763BBE0970072915946ED2E4CAC05D977F7D67
Question: What AES mode does SQL server 2012 use? Can it be changed?