Cipher-Project

Various ciphers are shown allowing for encryption and decryption of messages.

Ciphers Included

There are currently 4 separate ciphers included in the project. There are 5 separate options, however this is because there is one option for a ceasar cipher. This cipher is just a certain implementation of the shift cipher.

Shift Cipher

This cipher just takes in a message a key and then shifts all of the letters by that key. E_n(x) = (x + n) mod 26 D_n(x) = (x - n) mod 26

Vigenere Cipher

This cipher uses a key word to encrypt the message text. Each letter in the message text is shifted by the letters of the key word. Letters A-Z are equivalent to 0-25. The encryption E using the key of K is described as. E_k(M_i) = (M_i + K_{i mod m}) mod 26 D_k(C_i) = (C_i + K_{i mod m}) mod 26

RC4 (Rivest Cipher 4)

The breaking of this algorithm has lead to multiple vulnerabilities in WEP. The implementation of this algorithm includes the use of a PRG(Pseudo-random generator) and a KSA(Key-scheduling algorithm). Each value in the plaintext is xored with the next value in the PRG creating a encrypted text. The opposite allows for the decoding of the algorithm.

RSA (Rivest-Shamir-Adleman)

This is a public-key cryptosystem. The implementation of this algorithm is fairly straight forward.

1. p and q are generated as two distinct prime numbers to be kept secret
2. n is computed by performing p*q. n is part of the public key.
3. λ(n) = lcm(p-1, q-1)
4. Choose and integer 1 < e < λ(n) where gcd(e, λ(n)) = 1
5. Determin d that is the multiplicative inverse of e mod(λ(n)) Both n and e are distributed as the public key where d is the private key. Encryption: m^e = c(mod n) Decryption: c^d = (m^e)^d = m (mod n)