OpenSSL BIGNUM is very slow

[weikengchen]

It appears that the dominating overhead is that regardless of the domain size (which would be a more complicated issue when the domain is large), BIGNUM of OpenSSL is very bad --- and the performance would significantly be better with a more manual approach targeting the specific domain size that one is using.

[0NG]

You're right. For specific domains and native approaches, you can have a look at https://github.com/comForte/Format-Preserving-Encryption. For performance results, you may read Section 3 in their paper.

For this repo, I currently don't have time to implement native methods to improve the performance.

[weikengchen]

Thanks for the pointer!