> with(numtheory):
Warning, the protected name order has been redefined and unprotected
> 
> ## Susthma kruptografhshs ElGamal
> 
> ## Ypologismos parametrwn
> gen_params:=proc(digits)
> local R,g,p:
> R:=rand(10^(digits-1)..10^digits):
> p:=nextprime(R()):
> for g from 2 to p-1 while order(g,p) <> p-1 do 
> end do:
> RETURN([p,g]):
> end proc:
> 
> ## Ypologismos kleidiwn
> gen_keys:=proc(params)
> local R,x,y,g,p:
> p:=params[1]:
> g:=params[2]:
> R:=rand(1..p-1):
> x:=R():
> y:=g&^x mod p:
> RETURN([x,y]):
> end proc:
> 
> ## Kruptografhsh
> encrypt:=proc(m,params,public)
> local R,k,r,c,p,g:
> p:=params[1]:
> g:=params[2]:
> R:=rand(1..p-1):
> k:=R():
> r:=g&^k mod p;
> c:=m*public&^k mod p:
> RETURN([r,c]):
> end proc:
> 
> ## Apokruptografhsh
> decrypt:=proc(cipher,params,private)
> local c,r,m,p,g:
> p:=params[1]:
> g:=params[2]:
> r:=cipher[1]:
> c:=cipher[2]:
> m:=c*r&^(p-1-private) mod p:
> RETURN(m):
> end proc:
> 
> params:=gen_params(5);
                      params := [38011, 2]
> keys:=gen_keys(params);
                     keys := [30737, 19677]
> message:=1234;
                        message := 1234
> ciphertext:=encrypt(message,params,keys[2]);
                  ciphertext := [34108, 36974]
> plaintext:=decrypt(ciphertext,params,keys[1]);
                       plaintext := 1234
> params:=gen_params(30);
         params := [256126444952207781175113606349, 2]
> keys:=gen_keys(params);
keys := [248925881951877375747258092594, 29413043714189720611956139048]
> message:=12345678909876543212345678909;
            message := 12345678909876543212345678909
> ciphertext:=encrypt(message,params,keys[2]);
ciphertext := [237988914700200359164056814779, 129852134936760720564914849826]
> plaintext:=decrypt(ciphertext,params,keys[1]);
           plaintext := 12345678909876543212345678909
>