# I What resources are there for RSA for the layman?

Tags:
1. Apr 2, 2017

### matqkks

I am looking for any resources which explain the RSA algorithm for the layman. I have found a number of sources but they all tend to end with a morass of technical details. This is for a first year undergraduate course in number theory who have covered some basic work on modular arithmetic.

2. Apr 2, 2017

### aheight

I started with "A Concrete Introduction into Higher Algebra" by Lindsay Childs, Ch. 14. The chapter has a simple example. It' a little tough but try to muscle-through it. Good cooks try again.

3. Apr 2, 2017

### QuantumQuest

The steps of the algorithm in rough lines are

1 Generate two (large) prime numbers $p_1, p_2$ // steps 1, 2, 3, 4, 5 executed from server in advance
2 Take their product $k = p_1p_2$
3 Let function $f$ be such that $m = f(k) = (p_1 - 1)(p_2 - 1)$
4 Choose a prime number $p_3$ that is co-prime to $m$ with $GCD(m, p_3) = 1$ where $1 \lt p_3 \lt m$ // $k , p_3$ is the public key
5 Choose a number $n$ such that $p_3n \pmod m = 1$ //server keeps $n, m$ as its secret key
6 Encrypt message M: $E = M^{p_3} \pmod k$ // Browser encrypts the message using this formula and creates the encrypted E message
7 Decrypt message E: $M = E^n \pmod k$ // Server uses this math to decrypt E and effectively recover M

If you put some (preferably small in order to verify) numbers you can have a more practical sense about the algorithm.

4. Apr 2, 2017

### puzzled fish

I know of no better introduction than this excellent article to be found in an old Quantum magazine: Fermat’s Little Theorem (proving its value to mathematicians), V. Senderov and A. Spivak, May/Jun00, p14 (Feature)
http://static.nsta.org/pdfs/QuantumV10N5.pdf