(** Ciphers
    Built-in integer based ciphers.
*)

open Builtin
open Basic_arithmetics
open Power

(********** Cesar Cipher **********)

(** Cesar's cipher encryption
    @param k is an integer corresponding to key
    @param m word to cipher.
    @param b base ; for ASCII codes should be set to 255.
 *)
let encrypt_cesar k m b = []

(** Cesar's cipher decryption
    @param k is an integer corresponding to key
    @param m encrypted word.
    @param b base ; for ASCII code should be set to 255.
 *)
let decrypt_cesar k m b = []

(********** RSA Cipher **********)

(** Generate an RSA ciphering keys.
    Involved prime numbers need to be distinct. Output is a couple
    of public, private keys.
    @param p prime number
    @param q prime number
*)
let generate_keys_rsa p q = ((0,0), (0,0))


(** Encryption using RSA cryptosystem.
    @param m integer hash of message
    @param pub_key a tuple (n, e) composing public key of RSA cryptosystem.
 *)
let encrypt_rsa m (n, e) = 0

(** Decryption using RSA cryptosystem.
    @param m integer hash of encrypter message.
    @param pub_key a tuple (n, d) composing private key of RSA cryptosystem.
 *)
let decrypt_rsa m (n , d) = 0
;;

(********** ElGamal Cipher **********)

(** Generate ElGamal public data. Generates a couple (g, p)
    where p is prime and g having high enough order modulo p.
    @param p is prime having form 2*q + 1 for prime q.
 *)
let rec public_data_g p = (0, 0)

(** Generate ElGamal public data.
    @param pub_data a tuple (g, p) of public data for ElGamal cryptosystem.
 *)
let generate_keys_g (g, p) = (0, 0)

(** ElGamal encryption process.
    @param msg message to be encrypted.
    @param pub_data a tuple (g, p) of ElGamal public data.
    @param kA ElGamal public key.
 *)
let encrypt_g msg (g, p) kA = (0, 0)

(** ElGamal decryption process.
    @param msg a tuple (msgA, msgB) forming an encrypted ElGamal message.
    @param a private key
    @param pub_data a tuple (g, p) of public data for ElGamal cryptosystem.
 *)
let decrypt_g (msgA, msgB) a (g, p) = 0