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paillier.c
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paillier.c
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#include "paillier_internal.h"
#include <string.h>
#include <assert.h>
#include <openssl/err.h>
// WARNING: this function doesn't run in constant time!
int is_coprime_fast(const BIGNUM *in_a, const BIGNUM *in_b, BN_CTX *ctx)
{
BIGNUM *a, *b;
int ret = -1;
BN_CTX_start(ctx);
a = BN_CTX_get(ctx);
b = BN_CTX_get(ctx);
if (!a || !BN_copy(a, in_a))
goto cleanup;
if (!b || !BN_copy(b, in_b))
goto cleanup;
if (BN_cmp(a, b) < 0)
{
BIGNUM *t = b;
b = a;
a = t;
}
while (!BN_is_zero(b))
{
BIGNUM *t;
if (!BN_mod(a, a, b, ctx))
goto cleanup;
t = b;
b = a;
a = t;
}
ret = BN_is_one(a);
cleanup:
BN_CTX_end(ctx);
return ret;
}
static uint64_t L(BIGNUM *res, const BIGNUM *x, const BIGNUM *n, BN_CTX *ctx)
{
uint64_t ret = -1;
BIGNUM *x_copy = BN_dup(x);
if (!BN_sub_word(x_copy, 1))
goto cleanup;
if (!BN_div(res, NULL, x_copy, n, ctx))
goto cleanup;
ret = 0;
cleanup:
if (ret)
ret = ERR_get_error();
BN_clear_free(x_copy);
return ret;
}
long paillier_generate_key_pair(uint32_t key_len, paillier_public_key_t **pub, paillier_private_key_t **priv)
{
long ret = -1;
BIGNUM *p, *q, *tmp, *n, *n2, *lamda, *mu, *three, *four;
BN_CTX *ctx = NULL;
paillier_public_key_t *local_pub = NULL;
paillier_private_key_t *local_priv = NULL;
if (!pub || !priv)
return PAILLIER_ERROR_INVALID_PARAM;
if (key_len < MIN_KEY_LEN_IN_BITS)
return PAILLIER_ERROR_KEYLEN_TOO_SHORT;
if ((ctx = BN_CTX_secure_new()) == NULL)
return ERR_get_error() * -1;
*pub = NULL;
*priv = NULL;
BN_CTX_start(ctx);
tmp = BN_CTX_get(ctx);
three = BN_CTX_get(ctx);
four = BN_CTX_get(ctx);
p = BN_new();
q = BN_new();
n = BN_new();
n2 = BN_new();
lamda = BN_new();
mu = BN_new();
if (!p || !q || !tmp || !n || !n2 || !mu || !lamda || !three || !four)
goto cleanup;
BN_set_flags(n, BN_FLG_CONSTTIME);
BN_set_flags(n2, BN_FLG_CONSTTIME);
BN_set_flags(p, BN_FLG_CONSTTIME);
BN_set_flags(q, BN_FLG_CONSTTIME);
BN_set_flags(lamda, BN_FLG_CONSTTIME);
BN_set_flags(mu, BN_FLG_CONSTTIME);
if (!BN_set_word(three, 3))
goto cleanup;
if (!BN_set_word(four, 4))
goto cleanup;
// Choose two large prime p,q numbers having gcd(pq, (p-1)(q-1)) == 1
do
{
// p and q needs to be in the form of p = 4 * k + 3 to allow efficient calculation off fourth roots (needed in paillier blum zkp)
if (!BN_generate_prime_ex(p, key_len / 2, 0, four, three, NULL))
goto cleanup;
if (!BN_generate_prime_ex(q, key_len / 2, 0, four, three, NULL))
goto cleanup;
if (BN_num_bits(p) != BN_num_bits(q))
continue;
// Compute n = pq
if (!BN_mul(n, p, q, ctx))
goto cleanup;
if (!BN_sub(lamda, n, p))
goto cleanup;
if (!BN_sub(lamda, lamda, q))
goto cleanup;
if (!BN_add_word(lamda, 1))
goto cleanup;
}
while (BN_cmp(p, q) == 0 || !BN_gcd(tmp, lamda, n, ctx) || !BN_is_one(tmp));
if (!BN_sqr(n2, n, ctx))
goto cleanup;
// if num_bits(q) == num_bits(p), we can optimize g lambda and mu selection see https://en.wikipedia.org/wiki/Paillier_cryptosystem
if (!BN_mod_inverse(mu, lamda, n, ctx))
goto cleanup;
local_priv = (paillier_private_key_t*)malloc(sizeof(paillier_private_key_t));
if (!local_priv)
{
ret = PAILLIER_ERROR_OUT_OF_MEMORY;
goto cleanup;
}
local_priv->pub.n = n;
local_priv->pub.n2 = n2;
local_priv->p = p;
local_priv->q = q;
local_priv->lamda = lamda;
local_priv->mu = mu;
local_pub = (paillier_public_key_t*)malloc(sizeof(paillier_public_key_t));
if (!local_pub)
{
ret = PAILLIER_ERROR_OUT_OF_MEMORY;
goto cleanup;
}
local_pub->n = BN_dup(n);
local_pub->n2 = BN_dup(n2);
if (!local_pub->n || !local_pub->n2)
{
ret = PAILLIER_ERROR_OUT_OF_MEMORY;
goto cleanup;
}
*priv = local_priv;
*pub = local_pub;
ret = 0;
cleanup:
if (ret == -1)
ret = ERR_get_error() * -1;
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
if (ret)
{
// handle errors
if (local_priv)
free(local_priv);
paillier_free_public_key(local_pub); // as the public key uses duplication of n and n2 it's not sefficent just to free it
BN_free(p);
BN_free(q);
BN_free(n);
BN_free(n2);
BN_free(lamda);
BN_free(mu);
}
return ret;
}
long paillier_public_key_n(const paillier_public_key_t *pub, uint8_t *n, uint32_t n_len, uint32_t *n_real_len)
{
uint32_t len;
if (!pub)
return PAILLIER_ERROR_INVALID_KEY;
if (!n && n_len)
return PAILLIER_ERROR_INVALID_PARAM;
len = BN_num_bytes(pub->n);
if (n_real_len)
*n_real_len = len;
if (n_len < len)
return PAILLIER_ERROR_KEYLEN_TOO_SHORT;
return BN_bn2bin(pub->n, n) > 0 ? PAILLIER_SUCCESS : ERR_get_error() * -1;
}
uint32_t paillier_public_key_size(const paillier_public_key_t *pub)
{
if (pub)
return BN_num_bytes(pub->n) * 8;
return 0;
}
uint8_t *paillier_public_key_serialize(const paillier_public_key_t *pub, uint8_t *buffer, uint32_t buffer_len, uint32_t *real_buffer_len)
{
uint32_t needed_len = 0;
uint32_t n_len = 0;
uint8_t *p = buffer;
if (!pub)
return NULL;
n_len = (uint32_t)BN_num_bytes(pub->n);
needed_len = sizeof(uint32_t) + n_len;
if (real_buffer_len)
*real_buffer_len = needed_len;
if (!buffer || buffer_len < needed_len)
return NULL;
memcpy(p, &n_len, sizeof(uint32_t));
p += sizeof(uint32_t);
BN_bn2bin(pub->n, p);
return buffer;
}
paillier_public_key_t *paillier_public_key_deserialize(const uint8_t *buffer, uint32_t buffer_len)
{
paillier_public_key_t *pub;
uint32_t len = 0;
BN_CTX *ctx = NULL;
if (!buffer || buffer_len < (sizeof(uint32_t) + MIN_KEY_LEN_IN_BITS / 8))
return NULL;
pub = (paillier_public_key_t*)calloc(1, sizeof(paillier_public_key_t));
if (!pub)
return NULL;
memcpy(&len, buffer, sizeof(uint32_t));
assert(len == (buffer_len - sizeof(uint32_t)));
if (len > (buffer_len - sizeof(uint32_t)))
goto cleanup;
buffer_len -= sizeof(uint32_t);
buffer += sizeof(uint32_t);
pub->n = BN_bin2bn(buffer, len, NULL);
pub->n2 = BN_new();
if (!pub->n || !pub->n2)
goto cleanup;
if (BN_num_bits(pub->n) < MIN_KEY_LEN_IN_BITS)
goto cleanup;
ctx = BN_CTX_new();
if (!ctx || !BN_sqr(pub->n2, pub->n, ctx))
goto cleanup;
BN_CTX_free(ctx);
return pub;
cleanup:
BN_CTX_free(ctx);
paillier_free_public_key(pub);
return NULL;
}
void paillier_free_public_key(paillier_public_key_t *pub)
{
if (pub)
{
BN_free(pub->n);
BN_free(pub->n2);
free(pub);
}
}
long paillier_private_key_n(const paillier_private_key_t *priv, uint8_t *n, uint32_t n_len, uint32_t *n_real_len)
{
uint32_t len;
if (!priv)
return PAILLIER_ERROR_INVALID_KEY;
if (!n && n_len)
return PAILLIER_ERROR_INVALID_PARAM;
len = BN_num_bytes(priv->pub.n);
if (n_real_len)
*n_real_len = len;
if (n_len < len)
return PAILLIER_ERROR_KEYLEN_TOO_SHORT;
return BN_bn2bin(priv->pub.n, n) > 0 ? PAILLIER_SUCCESS : ERR_get_error() * -1;
}
const paillier_public_key_t* paillier_private_key_get_public(const paillier_private_key_t *priv)
{
if (priv)
return &priv->pub;
return NULL;
}
uint8_t *paillier_private_key_serialize(const paillier_private_key_t *priv, uint8_t *buffer, uint32_t buffer_len, uint32_t *real_buffer_len)
{
uint32_t needed_len = 0;
uint32_t p_len = 0;
uint8_t *p = buffer;
if (!priv)
return NULL;
p_len = (uint32_t)BN_num_bytes(priv->p);
assert(p_len == (uint32_t)BN_num_bytes(priv->q));
needed_len = sizeof(uint32_t) + 2 * p_len;
if (real_buffer_len)
*real_buffer_len = needed_len;
if (!buffer || buffer_len < needed_len)
return NULL;
memcpy(p, &p_len, sizeof(uint32_t));
p += sizeof(uint32_t);
BN_bn2bin(priv->p, p);
p +=p_len;
BN_bn2bin(priv->q, p);
return buffer;
}
paillier_private_key_t *paillier_private_key_deserialize(const uint8_t *buffer, uint32_t buffer_len)
{
paillier_private_key_t *priv;
uint32_t len = 0;
BN_CTX *ctx = NULL;
if (!buffer || buffer_len < (sizeof(uint32_t) + MIN_KEY_LEN_IN_BITS / 8)) // len(p) + len(q) == len(n)
return NULL;
priv = (paillier_private_key_t*)calloc(1, sizeof(paillier_private_key_t));
if (!priv)
return NULL;
memcpy(&len, buffer, sizeof(uint32_t));
assert(2 * len == (buffer_len - sizeof(uint32_t)));
if (2 * len > (buffer_len - sizeof(uint32_t)))
goto cleanup;
buffer_len -= sizeof(uint32_t);
buffer += sizeof(uint32_t);
priv->p = BN_bin2bn(buffer, len, NULL);
buffer += len;
priv->q = BN_bin2bn(buffer, len, NULL);
priv->pub.n = BN_new();
priv->pub.n2 = BN_new();
priv->lamda = BN_new();
priv->mu = BN_new();
if (!priv->p || !priv->q || !priv->lamda || !priv->mu || !priv->pub.n || !priv->pub.n2)
goto cleanup;
BN_set_flags(priv->p, BN_FLG_CONSTTIME);
BN_set_flags(priv->q, BN_FLG_CONSTTIME);
BN_set_flags(priv->pub.n, BN_FLG_CONSTTIME);
BN_set_flags(priv->pub.n2, BN_FLG_CONSTTIME);
BN_set_flags(priv->lamda, BN_FLG_CONSTTIME);
BN_set_flags(priv->mu, BN_FLG_CONSTTIME);
ctx = BN_CTX_new();
if (!ctx)
goto cleanup;
BN_CTX_start(ctx);
if (!BN_mul(priv->pub.n, priv->p, priv->q, ctx))
goto cleanup;
if (!BN_sqr(priv->pub.n2, priv->pub.n, ctx))
goto cleanup;
if (!BN_sub(priv->lamda, priv->pub.n, priv->p))
goto cleanup;
if (!BN_sub(priv->lamda, priv->lamda, priv->q))
goto cleanup;
if (!BN_add_word(priv->lamda, 1))
goto cleanup;
if (!BN_mod_inverse(priv->mu, priv->lamda, priv->pub.n, ctx))
goto cleanup;
if (BN_num_bits(priv->pub.n) < MIN_KEY_LEN_IN_BITS)
goto cleanup;
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return priv;
cleanup:
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
paillier_free_private_key(priv);
return NULL;
}
void paillier_free_private_key(paillier_private_key_t *priv)
{
if (priv)
{
BN_free(priv->pub.n);
BN_free(priv->pub.n2);
BN_clear_free(priv->p);
BN_clear_free(priv->q);
BN_clear_free(priv->lamda);
BN_clear_free(priv->mu);
free(priv);
}
}
long paillier_encrypt_openssl_internal(const paillier_public_key_t *key, BIGNUM *ciphertext, const BIGNUM *r, const BIGNUM *plaintext, BN_CTX *ctx)
{
int ret = -1;
// Verify that r E Zn*
if (is_coprime_fast(r, key->n, ctx) != 1)
return -PAILLIER_ERROR_INVALID_RANDOMNESS;
BN_CTX_start(ctx);
BIGNUM *tmp1 = BN_CTX_get(ctx);
BIGNUM *tmp2 = BN_CTX_get(ctx);
if (!tmp1 || !tmp2)
goto cleanup;
// Compute ciphertext = g^plaintext*r^n mod n^2
// as will select g=n+1 ciphertext = (1+n*plaintext)*r^n mod n^2, see https://en.wikipedia.org/wiki/Paillier_cryptosystem
if (!BN_mul(tmp1, key->n, plaintext, ctx))
goto cleanup;
if (!BN_add_word(tmp1, 1))
goto cleanup;
if (!BN_mod_exp(tmp2, r, key->n, key->n2, ctx))
goto cleanup;
if (!BN_mod_mul(ciphertext, tmp1, tmp2, key->n2, ctx))
goto cleanup;
ret = 0;
cleanup:
if (ret)
ret = ERR_peek_error();
BN_CTX_end(ctx);
return ret;
}
static inline uint64_t encrypt_openssl(const paillier_public_key_t *key, BIGNUM *ciphertext, const BIGNUM *plaintext, BN_CTX *ctx)
{
int ret = -1;
BN_CTX_start(ctx);
BIGNUM *r = BN_CTX_get(ctx);
if (!r)
ret = ERR_peek_error();
else
{
do
{
if (!BN_rand_range(r, key->n))
break;
ret = paillier_encrypt_openssl_internal(key, ciphertext, r, plaintext, ctx);
}
while (ret == -PAILLIER_ERROR_INVALID_RANDOMNESS);
}
BN_CTX_end(ctx);
return ret;
}
long paillier_decrypt_openssl_internal(const paillier_private_key_t *key, const BIGNUM *ciphertext, BIGNUM *plaintext, BN_CTX *ctx)
{
int ret = -1;
BN_CTX_start(ctx);
BIGNUM *tmp = BN_CTX_get(ctx);
if (!tmp)
goto cleanup;
// verify that ciphertext and n are coprime
if (is_coprime_fast(ciphertext, key->pub.n, ctx) != 1)
{
ret = PAILLIER_ERROR_INVALID_CIPHER_TEXT;
goto cleanup;
}
// Compute the plaintext = L(ciphertext^lamda mod n2)*mu mod n
if (!BN_mod_exp(tmp, ciphertext, key->lamda, key->pub.n2, ctx))
goto cleanup;
if (L(tmp, tmp, key->pub.n, ctx) != 0)
goto cleanup;
if (!BN_mod_mul(plaintext, tmp, key->mu, key->pub.n, ctx))
goto cleanup;
ret = 0;
cleanup:
if (ret)
ret = ERR_peek_error();
BN_CTX_end(ctx);
return ret;
}
long paillier_encrypt(const paillier_public_key_t *key, const uint8_t *plaintext, uint32_t plaintext_len, uint8_t *ciphertext, uint32_t ciphertext_len, uint32_t *ciphertext_real_len)
{
long ret = -1;
int len;
if (!key)
return PAILLIER_ERROR_INVALID_KEY;
if (!plaintext || plaintext_len > (uint32_t)BN_num_bytes(key->n))
return PAILLIER_ERROR_INVALID_PLAIN_TEXT;
if (ciphertext_real_len)
*ciphertext_real_len = (uint32_t)BN_num_bytes(key->n2);
if (!ciphertext || ciphertext_len < (uint32_t)BN_num_bytes(key->n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
BN_CTX *ctx = NULL;
BIGNUM *msg, *c;
if ((ctx = BN_CTX_new()) == NULL)
return ERR_get_error() * -1;
BN_CTX_start(ctx);
msg = BN_CTX_get(ctx);
if (!msg || !BN_bin2bn(plaintext, plaintext_len, msg))
goto cleanup;
if (BN_cmp(msg, key->n) >= 0)
{
// plaintext not in n
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return PAILLIER_ERROR_INVALID_PLAIN_TEXT;
}
c = BN_CTX_get(ctx);
if (!c)
goto cleanup;
ret = encrypt_openssl(key, c, msg, ctx);
if (ret)
goto cleanup;
len = BN_bn2bin(c, ciphertext);
if (len <= 0)
{
ret = PAILLIER_ERROR_UNKNOWN;
goto cleanup;
}
if (ciphertext_real_len)
*ciphertext_real_len = len;
if (len)
ret = PAILLIER_SUCCESS;
cleanup:
if (ret)
ret = ERR_get_error() * -1;
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ret;
}
long paillier_encrypt_to_ciphertext(const paillier_public_key_t *key, const uint8_t *plaintext, uint32_t plaintext_len, paillier_ciphertext_t **ciphertext)
{
long ret = -1;
paillier_ciphertext_t *c = NULL;
BN_CTX *ctx = NULL;
BIGNUM *msg;
if (!key)
return PAILLIER_ERROR_INVALID_KEY;
if (!plaintext || plaintext_len > (uint32_t)BN_num_bytes(key->n))
return PAILLIER_ERROR_INVALID_PLAIN_TEXT;
if (!ciphertext)
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
c = (paillier_ciphertext_t*)calloc(1, sizeof(paillier_ciphertext_t));
if (!c)
return PAILLIER_ERROR_OUT_OF_MEMORY;
if ((c->ciphertext = BN_new()) == NULL)
goto cleanup;
if ((c->r = BN_new()) == NULL)
goto cleanup;
if ((ctx = BN_CTX_new()) == NULL)
goto cleanup;
BN_CTX_start(ctx);
msg = BN_CTX_get(ctx);
if (!msg || !BN_bin2bn(plaintext, plaintext_len, msg))
goto cleanup;
if (BN_cmp(msg, key->n) >= 0)
{
// plaintext not in n
BN_CTX_end(ctx);
BN_CTX_free(ctx);
paillier_free_ciphertext(c);
return PAILLIER_ERROR_INVALID_PLAIN_TEXT;
}
do
{
if (!BN_rand_range(c->r, key->n))
break;
ret = paillier_encrypt_openssl_internal(key, c->ciphertext, c->r, msg, ctx);
}
while (ret == -PAILLIER_ERROR_INVALID_RANDOMNESS);
if (ret)
goto cleanup;
*ciphertext = c;
c = NULL;
ret = PAILLIER_SUCCESS;
cleanup:
if (ret > 0)
ret = ERR_get_error() * -1;
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
paillier_free_ciphertext(c);
return ret;
}
long paillier_encrypt_integer(const paillier_public_key_t *key, uint64_t plaintext, uint8_t *ciphertext, uint32_t ciphertext_len, uint32_t *ciphertext_real_len)
{
long ret = -1;
int len;
if (!key)
return PAILLIER_ERROR_INVALID_KEY;
if (ciphertext_real_len)
*ciphertext_real_len = (uint32_t)BN_num_bytes(key->n2);
if (!ciphertext || ciphertext_len < (uint32_t)BN_num_bytes(key->n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
BN_CTX *ctx = NULL;
BIGNUM *msg, *c;
if ((ctx = BN_CTX_new()) == NULL)
return ERR_get_error() * -1;
BN_CTX_start(ctx);
msg = BN_CTX_get(ctx);
if (!msg || !BN_set_word(msg, plaintext))
goto cleanup;
c = BN_CTX_get(ctx);
if (!c)
goto cleanup;
ret = encrypt_openssl(key, c, msg, ctx);
if (ret)
goto cleanup;
len = BN_bn2bin(c, ciphertext);
if (len <= 0)
{
ret = PAILLIER_ERROR_UNKNOWN;
goto cleanup;
}
if (ciphertext_real_len)
*ciphertext_real_len = len;
if (len)
ret = 0;
cleanup:
if (ret)
ret = ERR_get_error() * -1;
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ret;
}
long paillier_decrypt(const paillier_private_key_t *key, const uint8_t *ciphertext, uint32_t ciphertext_len, uint8_t *plaintext, uint32_t plaintext_len, uint32_t *plaintext_real_len)
{
long ret = PAILLIER_ERROR_OUT_OF_MEMORY;
int len;
if (!key)
return PAILLIER_ERROR_INVALID_KEY;
if (!ciphertext || ciphertext_len > (uint32_t)BN_num_bytes(key->pub.n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
if (plaintext_real_len)
*plaintext_real_len = (uint32_t)BN_num_bytes(key->pub.n);
if (!plaintext || plaintext_len < (uint32_t)BN_num_bytes(key->pub.n))
return PAILLIER_ERROR_INVALID_PLAIN_TEXT;
BN_CTX *ctx = NULL;
BIGNUM *msg, *c;
if ((ctx = BN_CTX_new()) == NULL)
return ERR_get_error() * -1;
BN_CTX_start(ctx);
c = BN_CTX_get(ctx);
if (!c || !BN_bin2bn(ciphertext, ciphertext_len, c))
goto cleanup;
if (BN_cmp(c, key->pub.n2) >= 0)
{
// ciphertext not in n^2
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
}
msg = BN_CTX_get(ctx);
if (!c)
goto cleanup;
ret = paillier_decrypt_openssl_internal(key, c, msg, ctx);
if (ret)
goto cleanup;
len = BN_bn2bin(msg, plaintext);
if (len <= 0)
{
ret = PAILLIER_ERROR_UNKNOWN;
goto cleanup;
}
if (plaintext_real_len)
*plaintext_real_len = len;
if (len)
ret = 0;
cleanup:
if (ret)
ret = ERR_get_error() * -1;
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ret;
}
long paillier_decrypt_integer(const paillier_private_key_t *key, const uint8_t *ciphertext, uint32_t ciphertext_len, uint64_t *plaintext)
{
if (!key)
return PAILLIER_ERROR_INVALID_KEY;
if (ciphertext_len > (uint32_t)BN_num_bytes(key->pub.n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
if (!plaintext)
return PAILLIER_ERROR_INVALID_PLAIN_TEXT;
long ret = -1;
int openssl_error = 1;
BN_CTX *ctx = NULL;
BIGNUM *msg, *c;
if ((ctx = BN_CTX_new()) == NULL)
return ERR_get_error() * -1;
BN_CTX_start(ctx);
c = BN_CTX_get(ctx);
if (!c || !BN_bin2bn(ciphertext, ciphertext_len, c))
goto cleanup;
if (BN_cmp(c, key->pub.n2) >= 0)
{
// ciphertext not in n^2
ret = PAILLIER_ERROR_INVALID_CIPHER_TEXT;
openssl_error = 0;
goto cleanup;
}
msg = BN_CTX_get(ctx);
if (!c)
goto cleanup;
ret = paillier_decrypt_openssl_internal(key, c, msg, ctx);
if (ret)
goto cleanup;
if ((uint32_t)BN_num_bytes(msg) > sizeof(*plaintext))
{
ret = PAILLIER_ERROR_INVALID_PLAIN_TEXT;
openssl_error = 0;
goto cleanup;
}
*plaintext = BN_get_word(msg);
ret = 0;
cleanup:
if (ret && openssl_error)
ret = ERR_get_error() * -1;
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ret;
}
long paillier_add(const paillier_public_key_t *key, const uint8_t *a_ciphertext, uint32_t a_ciphertext_len, const uint8_t *b_ciphertext, uint32_t b_ciphertext_len,
uint8_t *result, uint32_t result_len, uint32_t *result_real_len)
{
BN_CTX *ctx = NULL;
BIGNUM *a = NULL;
BIGNUM *b = NULL;
BIGNUM *res = NULL;
long ret = -1;
int len = 0;
if (!key)
return PAILLIER_ERROR_INVALID_KEY;
if (!a_ciphertext || a_ciphertext_len > (uint32_t)BN_num_bytes(key->n2) ||
!b_ciphertext || b_ciphertext_len > (uint32_t)BN_num_bytes(key->n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
if (result_real_len)
*result_real_len = (uint32_t)BN_num_bytes(key->n2);
if (!result || result_len < (uint32_t)BN_num_bytes(key->n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
if ((ctx = BN_CTX_new()) == NULL)
return ERR_get_error() * -1;
BN_CTX_start(ctx);
a = BN_CTX_get(ctx);
if (!a || !BN_bin2bn(a_ciphertext, a_ciphertext_len, a))
goto cleanup;
b = BN_CTX_get(ctx);
if (!b || !BN_bin2bn(b_ciphertext, b_ciphertext_len, b))
goto cleanup;
res = BN_CTX_get(ctx);
if (!res)
goto cleanup;
// verify that a_ciphertext and b_ciphertext are coprime to n
if (is_coprime_fast(a, key->n, ctx) != 1 ||
is_coprime_fast(b, key->n, ctx) != 1)
{
ret = PAILLIER_ERROR_INVALID_CIPHER_TEXT;
goto cleanup;
}
if (!BN_mod_mul(res, a, b, key->n2, ctx))
goto cleanup;
len = BN_bn2bin(res, result);
if (len <= 0)
{
ret = PAILLIER_ERROR_UNKNOWN;
goto cleanup;
}
if (result_real_len)
*result_real_len = len;
if (len)
ret = 0;
cleanup:
if (ret)
ret = ERR_get_error() * -1;
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ret;
}
long paillier_add_integer(const paillier_public_key_t *key, const uint8_t *a_ciphertext, uint32_t a_ciphertext_len, uint64_t b, uint8_t *result, uint32_t result_len, uint32_t *result_real_len)
{
BN_CTX *ctx = NULL;
BIGNUM *bn_a = NULL;
BIGNUM *bn_b = NULL;
BIGNUM *res = NULL;
long ret = -1;
int len = 0;
if (!key)
return PAILLIER_ERROR_INVALID_KEY;
if (!a_ciphertext || a_ciphertext_len > (uint32_t)BN_num_bytes(key->n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
if (result_real_len)
*result_real_len = (uint32_t)BN_num_bytes(key->n2);
if (!result || result_len < (uint32_t)BN_num_bytes(key->n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
if ((ctx = BN_CTX_new()) == NULL)
return ERR_get_error() * -1;
BN_CTX_start(ctx);
bn_a = BN_CTX_get(ctx);
if (!bn_a || !BN_bin2bn(a_ciphertext, a_ciphertext_len, bn_a))
goto cleanup;
bn_b = BN_CTX_get(ctx);
if (!bn_b || !BN_set_word(bn_b, b))
goto cleanup;
res = BN_CTX_get(ctx);
if (!res)
goto cleanup;
// verify that a_ciphertext and n are coprime
if (is_coprime_fast(bn_a, key->n, ctx) != 1)
{
ret = PAILLIER_ERROR_INVALID_CIPHER_TEXT;
goto cleanup;
}
ret = encrypt_openssl(key, res, bn_b, ctx);
if (ret)
goto cleanup;
if (!BN_mod_mul(res, bn_a, res, key->n2, ctx))
goto cleanup;
len = BN_bn2bin(res, result);
if (len <= 0)
{
ret = PAILLIER_ERROR_UNKNOWN;
goto cleanup;
}
if (result_real_len)
*result_real_len = len;
if (len)
ret = 0;
cleanup:
if (ret)
ret = ERR_get_error() * -1;
if (ctx)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ret;
}
long paillier_sub(const paillier_public_key_t *key, const uint8_t *a_ciphertext, uint32_t a_ciphertext_len, const uint8_t *b_ciphertext, uint32_t b_ciphertext_len,
uint8_t *result, uint32_t result_len, uint32_t *result_real_len)
{
BN_CTX *ctx = NULL;
BIGNUM *a = NULL;
BIGNUM *b = NULL;
BIGNUM *res = NULL;
long ret = -1;
int len = 0;
if (!key)
return PAILLIER_ERROR_INVALID_KEY;
if (!a_ciphertext || a_ciphertext_len > (uint32_t)BN_num_bytes(key->n2) ||
!b_ciphertext || b_ciphertext_len > (uint32_t)BN_num_bytes(key->n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
if (result_real_len)
*result_real_len = (uint32_t)BN_num_bytes(key->n2);
if (!result || result_len < (uint32_t)BN_num_bytes(key->n2))
return PAILLIER_ERROR_INVALID_CIPHER_TEXT;
if ((ctx = BN_CTX_new()) == NULL)
return ERR_get_error() * -1;
BN_CTX_start(ctx);
a = BN_CTX_get(ctx);
if (!a || !BN_bin2bn(a_ciphertext, a_ciphertext_len, a))
goto cleanup;
b = BN_CTX_get(ctx);
if (!b || !BN_bin2bn(b_ciphertext, b_ciphertext_len, b))
goto cleanup;
res = BN_CTX_get(ctx);
if (!res)
goto cleanup;
// verify that a_ciphertext and b_ciphertext are coprime to n