Good day everyone! Please bear with me as this is my first post on the crypto exchange. An interesting question was raised in a meeting recently about the double-encryption problem (i.e. same algorithm used on same message block twice yields weaker results). However, the team was concerned that database encryption (such as Oracle or SQL Server's TDE) along-side SAN encryption might cause weaknesses.
For example, Wikipedia states (en.wikipedia.org/wiki/Multiple_encryption): "Picking any two ciphers, if the key used is the same for both, the second cipher could possibly undo the first cipher, partly or entirely. This is true of ciphers where the decryption process is exactly the same as the encryption process—the second cipher would completely undo the first."
However, my understanding is that TDE protects against a SAN admin decrypting the disks and walking out with a copy of the database. Not having TDE would be frowned upon by infosec unless it demonstrably causes weaknesses.
So when does double-encryption issues apply, or does it not at all here? I am more hoping to understand the rationale behind when this does/does not apply.