I have been reading Simons singh's Book 'Code book' and found the section on Public key distributon very interesting. In the appendix he describes the method of encoding and decoding a number. In the decoding section he states the following formula:

e x d = 1(MOD(p-1) x (q-1)), e= 7 p=17 & q=11
7 x d = 1(MOD 160)
d= 23

He says deducing d is not straight forward, but using Euclids algorithm, d can be calculated.

Could you shed some light on probly what is a very trivial problem

Cheers Dan