void Decrypt_BC_KEM_using_indicies(global_broadcast_params_t gbp,
priv_key_t mykey, element_t key,
ct_t myct, int *in_recip, int num_recip)
{
if(!mykey) {
printf("\nyou didn't give me a valid key. I die\n");
return;
}
Gen_decr_prod_from_indicies(gbp, mykey->index,in_recip, num_recip, mykey);
DecryptKEM_using_product(gbp, mykey, key, myct);
}
int BCEDecrypt(byte *global_params_path, byte *priv_key_block, byte *CT_C0, byte *CT_C1, byte *symmetric_key_out)
{
global_broadcast_params_t gbs;
priv_key_t priv_key;
ct_t shared_CT;
element_t symmetric_key;
int suffix = 0, retlen;
if (global_params_path == NULL)
return 1;
if (priv_key_block == NULL)
return 2;
if (CT_C0 == NULL)
return 3;
if (CT_C1 == NULL)
return 4;
if (symmetric_key_out == NULL)
return 5;
LoadGlobalParams((char *) global_params_path, &gbs);
priv_key = (priv_key_t) pbc_malloc(sizeof(struct single_priv_key_s));
// restore index
priv_key->index = bytes_to_int(priv_key_block);
suffix += PRK_INDEX_LENGTH;
// restore g_i_gamma
element_init(priv_key->g_i_gamma, gbs->pairing->G1);
retlen = element_from_bytes(priv_key->g_i_gamma, priv_key_block + suffix);
if (retlen != PRK_G_I_GAMMA_LENGTH)
return 6;
suffix += PRK_G_I_GAMMA_LENGTH;
// restore g_i
element_init(priv_key->g_i, gbs->pairing->G1);
retlen = element_from_bytes(priv_key->g_i, priv_key_block + suffix);
if (retlen != PRK_G_I_LENGTH)
return 7;
suffix += PRK_G_I_LENGTH;
// restore h_i
element_init(priv_key->h_i, gbs->pairing->G2);
retlen = element_from_bytes(priv_key->h_i, priv_key_block + suffix);
if (retlen != PRK_H_I_LENGTH)
return 8;
suffix += PRK_H_I_LENGTH;
// restore decr_prod
element_init(priv_key->decr_prod, gbs->pairing->G1);
retlen = element_from_bytes(priv_key->decr_prod, priv_key_block + suffix);
if (retlen != PRK_DECR_PROD_LENGTH)
return 9;
shared_CT = (ct_t) pbc_malloc(sizeof(struct ciphertext_s));
element_init(shared_CT->C0, gbs->pairing->G2);
element_init(shared_CT->C1, gbs->pairing->G1);
element_from_bytes(shared_CT->C0, CT_C0);
element_from_bytes(shared_CT->C1, CT_C1);
DecryptKEM_using_product(gbs, priv_key, symmetric_key, shared_CT);
retlen = element_to_bytes(symmetric_key_out, symmetric_key);
if (retlen != SYMMETRIC_KEY_LENGTH)
return 10;
element_random(symmetric_key);
element_clear(symmetric_key);
FreeCT(shared_CT);
pbc_free(shared_CT);
FreePK(priv_key);
pbc_free(priv_key);
FreeGBP(gbs);
pbc_free(gbs);
return 0;
}