python3, sympy 1.4.
Download all files and run SPN.py. Run it in terminal for best results.
Check out the wiki for documentation and more stuff about this project: https://github.com/deepankar715/Encryption-Decryption-SPN/wiki
This program is rather dirty because of the hurry in which I had to write it. I might need to beautify it eventually. See the improvements section in wiki for more details.
Do NOT to use any non standard cryptographic algorithm for anything serious. 99% of the algorithms out there are unsafe to use.