lindsaymacvean/assymetricencryption

Asymmetric Cryptographic Example

This is an example of asymmetric cryptography with both an encryption and decryption method.

Requirements to run

Python 3 and above.

Getting Started

git clone url
python main.py

Then enter an option to either encrypt the contents of encrypt.txt file or decrypt the contents of decrypt.txt

Cryptographic explanation

The simplest and the original implementation of the first asymmetric cryptographic protocol uses the multiplicative group of integers modulo p, where p is prime, and g is a primitive root modulo p. These two values are chosen in this way to ensure that the resulting shared secret can take on any value from 1 to p–1. Here is an example of the protocol.

1. Alice and Bob agree to use a modulus p = 23 and base g = 5 (which is a primitive root modulo 23).
2. Alice chooses a secret key a = 4, then sends Bob a public key A = g^a mod p
   A = 5⁴ mod 23 = 4
3. Bob chooses a secret key b = 3, then sends Alice a public key B = g^b mod p
   B = 5³ mod 23 = 10
4. Alice uses Bob's public key and her private key to compute a shared secret s = B^a mod p
   s = 10⁴ mod 23 = 18
5. Bob uses Alice's public key and his private key to compute the same shared secret s = Ab mod p
   s = 4³ mod 23 = 18
6. Alice and Bob now share a secret (the number 18), which can be used as a key to do symmetric encryption on large pieces of content.

References

https://en.wikipedia.org/wiki/Public-key_cryptography https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange