I have looked through the whole set of "Oracle Database 11g Release 2 (11.2) Documentation" searching for the details of the master encryption key used for transparent data encryption (TDE) with HSM. There was only a single insignificant line out of the whole set of documentation that says it makes use of AES.
What surprised me was that no word was mentioned of the AES mode (CBC, ECB, etc) and the key length for the master key that was generated using the following command when it could have been important information for most. Did I miss something? Does anybody has any ideas?
SQL> ALTER SYSTEM SET ENCRYPTION KEY IDENTIFIED BY "user_Id:password"
The following answer is as quoted from Oracle Forum.
"Oracle TDE asks the HSM via PKCS#11 specifically to generate an AES256 key."