# How many rounds of encryption is ideal?

I am a newbie to the cryptography world. I am working on a custom algorithm that encrypts the data multiple times and results in a cipher text. It uses a different key in each round to encrypt it. I researched a lot but couldn't find any answer to this question. What do you think is the ideal number for the rounds of encryption when the keys are different in each iteration? Could you show me some math?

Alex

• optimal round count depends on the round structure, the key schedule, and the required security from the cipher Commented Oct 9, 2018 at 2:05
• And if your "round" is actually just a standard application of a strong cipher like AES the answer is "1". Commented Oct 9, 2018 at 6:47
• @SEJPM That was already covered in the previous question of Lock Smith / Alex; this is a logical followup to that question. Unfortunately, we cannot really answer because of the reason stated by Richie: AES has 10 rounds (minimum) while Threefish has a simpler structure and 80 rounds.... Commented Oct 9, 2018 at 18:00
• and this question Commented Oct 9, 2018 at 18:53

• @just_learning The big $\mathcal{O}$ notation is basically the order of operations. what an operation is is context specific. Normally you'd use it for a single block encrypt / decrypt of the block cipher (presuming that that's needed to attack the cipher). However, you can define it to be a single round as well; in short, $\mathcal{O}$ is context specific. Commented Aug 22, 2023 at 21:35