Most RDBMS support encrypt/decrypt functions a key, and the supported algorithm is AES. the block size is 16 bytes, with TEIID-4643, encrypt/decrypt functions should be pushdown. Below are some links of DB vendor's encrypt/decrypt functions.

[1] https://dev.mysql.com/doc/refman/5.5/en/encryption-functions.html
[2] http://www.h2database.com/html/functions.html#encrypt
[3] https://mariadb.com/kb/en/mariadb/encryption-hashing-and-compression-functions/