Re: Same query with different response time

  • From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Mon, 28 Jun 2021 00:01:41 -0400

IO has changed because encrypted data is much larger than the original. Encrypted data can be 4 times or more larger than the original. That is what happens when you apply ciphers like RSA RC4. There are many decryption techniques that are being stymied by this: pattern recognition, same character repeat and many others. Since the keys are enormous, you would need 100 years or so to break them. Public key encryption is based on huge numbers that need to be factored into their prime components. The most efficient factorization algorithm is the Sieve of Erathosten, named after mathematician form the ancient Greece. So, unless some mathematical wunderkind comes up with something much faster, your data is safe and secure. That hasn't happened for the last 2500 years or so. The price you pay is much enlarged data size and a lot of CPU cycles to decrypt stuff. Personally, I use ROT13 and, to be safe, I encrypt everything - twice.

On 6/27/21 10:18 PM, Lok P wrote:

No other change happened. It was only tablespace encryption which has been done on top of existing data.

I am also struggling to understand why the increase in IO is noted in SQL monitor.

Mladen Gogala
Database Consultant
Tel: (347) 321-1217


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