/*
 encrypt.c - EPOC-1 encryption function

 Copyright NTT MCL, 2000.

 Duncan S Wong
 Security Group, NTT MCL
 July 2000
*/

#include <stdio.h>
#include <gmp.h>
#include "epoc1.h"
#include "hash.h"

/*
 EPOC-1 encryption

 Return: TRUE if succeed; otherwise FALSE
*/
BYTE EPOC1_Encryption (
   BYTE             *message,       /* plaintext */
   EPOC1_PUB_KEY    *publicKey,     /* EPOC1 public key */
   BYTE             *ciphertext     /* returned ciphertext */
)
{
mpz_t R, m, r, m_n_R, comp1, comp2, C;
gmp_randstate_t state;
BYTE *H_in, *tmp_p, *m_raw, *R_raw, *r_raw;
WORD H_in_len;
long i;

	mpz_init(R);
	mpz_init(m);
	mpz_init(r);
	mpz_init(m_n_R);
	mpz_init(comp1);
	mpz_init(comp2);
	mpz_init(C);
	m_raw = (BYTE *) malloc (publicKey->mLen/8);
	r_raw = (BYTE *) malloc (publicKey->hLen/8);
	R_raw = (BYTE *) malloc (publicKey->rLen/8);

	memset(m_raw, 0, publicKey->mLen/8);

	/* prepare (mpz_t) m and (BYTE *) m_raw */
	mpz_set_str(m, message, 0);

	WORD2BYTE(m_raw+(publicKey->mLen/8-ABS(m->_mp_size)*4), m->_mp_d,
	          ABS(m->_mp_size));
	/*
	printf("EPOC1_Encryption: m_raw =\n");
	for(i=0; i< publicKey->mLen/8; i++)
		printf("%02x ", m_raw[i]);
	printf("\n\n");
	*/

	/* generate R */
	gmp_randinit(state, GMP_RAND_ALG_LC, publicKey->rLen);
	mpz_urandomb (R, state, publicKey->rLen);
	printf("R = 0x%s\n", mpz_get_str(NULL, 16, R));

	WORD2BYTE(R_raw, R->_mp_d, ABS(R->_mp_size));

	/*
	printf("EPOC1_Encryption: R_raw =\n");
	for(i=0; i< publicKey->rLen/8; i++)
		printf("%02x ", R_raw[i]);
	printf("\n\n");
	*/

	/* compute m_n_R := (m || R) and r := H(m || R) */
	H_in_len = (publicKey->mLen + publicKey->rLen)/8;
	H_in = (BYTE *) malloc (H_in_len);
	tmp_p = H_in;
	assignBYTE(tmp_p, m_raw, publicKey->mLen/8);
	tmp_p += publicKey->mLen/8;
	assignBYTE(tmp_p, R_raw, publicKey->rLen/8);
	BYTE2WORD( m_n_R, H_in, H_in_len );

	/*
	printf("EPOC1_Encryption: m_n_R=\n");
	printf("%s\n\n", mpz_get_str(NULL, 16, m_n_R));
	printf("EPOC1_Encryption: H_in =\n");
	for(i=0; i< H_in_len; i++)
		printf("%02x ", H_in[i]);
	printf("\n\n");
	*/

	indexedSHA (r_raw, publicKey->hLen/8, H_in, H_in_len);

	BYTE2WORD( r, r_raw, publicKey->hLen/8);
	printf("r = 0x%s\n", mpz_get_str(NULL, 16, r));

	/* compute C */
	mpz_powm(comp1, publicKey->g, m_n_R, publicKey->n);

	mpz_powm(comp2, publicKey->h, r, publicKey->n);

	mpz_mul(C, comp1, comp2);
	mpz_mod(C, C, publicKey->n);
	/*
	printf("EPOC1_Encryption: C =\n");
	printf("%s\n\n", mpz_get_str(NULL, 16, C));
	*/

	sprintf(ciphertext, "0x%s", mpz_get_str(NULL, 16, C));

	/* clean up */
	mpz_clear(R);
	mpz_clear(m);
	mpz_clear(r);
	mpz_clear(m_n_R);
	mpz_clear(comp1);
	mpz_clear(comp2);
	mpz_clear(C);

	memset(m_raw, 0, publicKey->mLen/8);
	memset(r_raw, 0, publicKey->hLen/8);
	memset(R_raw, 0, publicKey->rLen/8);
	memset(H_in,  0, H_in_len);
	free(m_raw);
	free(r_raw);
	free(R_raw);
	free(H_in);

	H_in_len = 0;

	return TRUE;
}