/*
 * Alice wishes to sign a message. She generates her public and private keys as follows. Her private key is a random element x of Zr, and her corresponding public key is g^x.
 * To sign a message, Alice hashes the message to some element h of G1, and then outputs the signature h^x.
 * To verify a signature σ, Bob checks that e(h,g^x) = e(σ, g).
 *
 *
 * */
#include <pbc/pbc.h>
#include <pbc/pbc_test.h>

int main(int argc, char **argv)
{
    // declare g and h random elements from G1 and G2 respectively
    element_t g, h;

    // public and private key of alice
    element_t public_key, private_key;
    element_t sig;
    element_t temp1, temp2;

    pairing_t pairing;
    //char param[1024];
    //size_t count = fread(param, 1, 1024, stdin);
    //if (!count) pbc_die("input error");
    //pairing_init_set_buf(pairing, param, count);
    pbc_demo_pairing_init(pairing, argc, argv);

    // initialise all elements and keys
    element_init_G2(g, pairing);
    element_init_G2(public_key, pairing);
    element_init_G1(h, pairing);
    element_init_G1(sig, pairing);
    element_init_GT(temp1, pairing);
    element_init_GT(temp2, pairing);
    element_init_Zr(private_key, pairing);

    // pick system parameter g
    element_random(g);
    element_printf(" g = %B\n", g);

    // Alice generates private key
        element_random(private_key);
        element_printf("Alices random private key = %B\n", private_key);

    // Alice generates public key, which is g^(private_key)
    element_pow_zn(public_key, g, private_key);
        element_printf("Alices random public key = %B\n", public_key);

    //Now Alice will sign a message
    printf("=============Now Alice will hash the message==============\n");
    element_from_hash(h, "Alice wants to kill you", 20);

        element_printf("Alices hash to element h = %B\n", h);

    //Sign the message
    element_pow_zn(sig, h, private_key);

    // Bob verifies the signature
    pairing_apply(temp1, sig, g, pairing);
    pairing_apply(temp2, h, public_key, pairing);
    if (!element_cmp(temp1, temp2)) {
            printf("signature verifies\n");
    } else {
            printf("signature does not verify\n");
    }

    return 0;
}