Cryptography Decoder

[fighterfighter]

I need some help creating a code for my cryptography decoder. The user enters two values (n,e) and the code enters a loop find a value d such that:
e * d = 1 mod n ( n is the Euler totient function or φ(n), e is invertible in Z(phi(n)) and d is its inverse). I have a code to find the phi(n)/φ(n), but I can't figure out a way to find d.

Thanks.

[jmcilhinney]

This is a maths question, not a programming question. You need to work out what to do mathematically first and, only then, you would work out how to implement that maths in code. This site has a Math forum. I have suggested to the mods that this thread should be moved there.

[FunkyDexter]

Moved to Maths forum. As JMc says, you're more likely to get a decent response in there for a question that's this maths heavy.

And welcome to the forum