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-rw-r--r--src/lib/math/mp/mp_core.cpp4
-rw-r--r--src/lib/math/numbertheory/make_prm.cpp90
-rw-r--r--src/lib/math/numbertheory/numthry.h16
3 files changed, 73 insertions, 37 deletions
diff --git a/src/lib/math/mp/mp_core.cpp b/src/lib/math/mp/mp_core.cpp
index 4ed61ac38..ffa5b31a8 100644
--- a/src/lib/math/mp/mp_core.cpp
+++ b/src/lib/math/mp/mp_core.cpp
@@ -436,10 +436,14 @@ word bigint_divop(word n1, word n0, word d)
*/
word bigint_modop(word n1, word n0, word d)
{
+#if defined(BOTAN_HAS_MP_DWORD)
+ return ((static_cast<dword>(n1) << MP_WORD_BITS) | n0) % d;
+#else
word z = bigint_divop(n1, n0, d);
word dummy = 0;
z = word_madd2(z, d, &dummy);
return (n0-z);
+#endif
}
}
diff --git a/src/lib/math/numbertheory/make_prm.cpp b/src/lib/math/numbertheory/make_prm.cpp
index f06f1978e..419252ed6 100644
--- a/src/lib/math/numbertheory/make_prm.cpp
+++ b/src/lib/math/numbertheory/make_prm.cpp
@@ -16,20 +16,22 @@ namespace Botan {
*/
BigInt random_prime(RandomNumberGenerator& rng,
size_t bits, const BigInt& coprime,
- size_t equiv, size_t modulo)
+ size_t equiv, size_t modulo,
+ size_t prob)
{
- if(coprime <= 0)
+ if(coprime.is_negative())
{
- throw Invalid_Argument("random_prime: coprime must be > 0");
+ throw Invalid_Argument("random_prime: coprime must be >= 0");
}
- if(modulo % 2 == 1 || modulo == 0)
+ if(modulo == 0)
{
throw Invalid_Argument("random_prime: Invalid modulo value");
}
- if(equiv >= modulo || equiv % 2 == 0)
- {
- throw Invalid_Argument("random_prime: equiv must be < modulo, and odd");
- }
+
+ equiv %= modulo;
+
+ if(equiv == 0)
+ throw Invalid_Argument("random_prime Invalid value for equiv/modulo");
// Handle small values:
if(bits <= 1)
@@ -50,6 +52,9 @@ BigInt random_prime(RandomNumberGenerator& rng,
return ((rng.next_byte() % 2) ? 11 : 13);
}
+ secure_vector<uint16_t> sieve(PRIME_TABLE_SIZE);
+ const size_t MAX_ATTEMPTS = 32*1024;
+
while(true)
{
BigInt p(rng, bits);
@@ -59,21 +64,18 @@ BigInt random_prime(RandomNumberGenerator& rng,
p.set_bit(bits - 2);
p.set_bit(0);
- if(p % modulo != equiv)
- p += (modulo - p % modulo) + equiv;
+ // Force p to be equal to equiv mod modulo
+ p += (modulo - (p % modulo)) + equiv;
- const size_t sieve_size = std::min(bits / 2, PRIME_TABLE_SIZE);
- secure_vector<uint16_t> sieve(sieve_size);
-
- for(size_t j = 0; j != sieve.size(); ++j)
- sieve[j] = static_cast<uint16_t>(p % PRIMES[j]);
+ for(size_t i = 0; i != sieve.size(); ++i)
+ sieve[i] = static_cast<uint16_t>(p % PRIMES[i]);
size_t counter = 0;
while(true)
{
++counter;
- if(counter >= 4096)
+ if(counter > MAX_ATTEMPTS)
{
break; // don't try forever, choose a new starting point
}
@@ -84,26 +86,39 @@ BigInt random_prime(RandomNumberGenerator& rng,
break;
bool passes_sieve = true;
- for(size_t j = 0; j != sieve.size(); ++j)
+ for(size_t i = 0; i != sieve.size(); ++i)
{
- sieve[j] = (sieve[j] + modulo) % PRIMES[j];
- if(sieve[j] == 0)
- {
+ sieve[i] = (sieve[i] + modulo) % PRIMES[i];
+
+ /*
+ In this case, p is a multiple of PRIMES[i]
+ */
+ if(sieve[i] == 0)
+ passes_sieve = false;
+
+ /*
+ In this case, 2*p+1 will be a multiple of PRIMES[i]
+
+ So if generating a safe prime, we want to avoid this value
+ because 2*p+1 will not be useful. Since the check is cheap to
+ do and doesn't seem to affect the overall distribution of the
+ generated primes overmuch it's used in all cases.
+
+ See "Safe Prime Generation with a Combined Sieve" M. Wiener
+ https://eprint.iacr.org/2003/186.pdf
+ */
+ if(sieve[i] == PRIMES[i] / 2)
passes_sieve = false;
- break;
- }
}
if(!passes_sieve)
continue;
- if(gcd(p - 1, coprime) != 1)
+ if(coprime > 0 && gcd(p - 1, coprime) != 1)
continue;
- if(is_prime(p, rng, 128, true))
- {
+ if(is_prime(p, rng, prob, true))
return p;
- }
}
}
}
@@ -117,12 +132,25 @@ BigInt random_safe_prime(RandomNumberGenerator& rng, size_t bits)
throw Invalid_Argument("random_safe_prime: Can't make a prime of " +
std::to_string(bits) + " bits");
- BigInt p;
- do
- p = (random_prime(rng, bits - 1) << 1) + 1;
- while(!is_prime(p, rng, 128, true));
+ BigInt q, p;
+ for(;;)
+ {
+ /*
+ Generate q == 2 (mod 3)
+
+ Otherwise [q == 1 (mod 3) case], 2*q+1 == 3 (mod 3) and not prime.
+ */
+ q = random_prime(rng, bits - 1, 1, 2, 3, 8);
+ p = (q << 1) + 1;
- return p;
+ if(is_prime(p, rng, 128, true))
+ {
+ // We did only a weak check before, go back and verify q before returning
+ if(is_prime(q, rng, 128, true))
+ return p;
+ }
+
+ }
}
}
diff --git a/src/lib/math/numbertheory/numthry.h b/src/lib/math/numbertheory/numthry.h
index 7d37ea1b7..b002ace91 100644
--- a/src/lib/math/numbertheory/numthry.h
+++ b/src/lib/math/numbertheory/numthry.h
@@ -164,9 +164,9 @@ size_t BOTAN_PUBLIC_API(2,0) low_zero_bits(const BigInt& x);
* @return true if all primality tests passed, otherwise false
*/
bool BOTAN_PUBLIC_API(2,0) is_prime(const BigInt& n,
- RandomNumberGenerator& rng,
- size_t prob = 56,
- bool is_random = false);
+ RandomNumberGenerator& rng,
+ size_t prob = 56,
+ bool is_random = false);
inline bool quick_check_prime(const BigInt& n, RandomNumberGenerator& rng)
{ return is_prime(n, rng, 32); }
@@ -186,11 +186,15 @@ inline bool verify_prime(const BigInt& n, RandomNumberGenerator& rng)
* @param equiv a non-negative number that the result should be
equivalent to modulo equiv_mod
* @param equiv_mod the modulus equiv should be checked against
+* @param prob use test so false positive is bounded by 1/2**prob
* @return random prime with the specified criteria
*/
BigInt BOTAN_PUBLIC_API(2,0) random_prime(RandomNumberGenerator& rng,
- size_t bits, const BigInt& coprime = 1,
- size_t equiv = 1, size_t equiv_mod = 2);
+ size_t bits,
+ const BigInt& coprime = 0,
+ size_t equiv = 1,
+ size_t equiv_mod = 2,
+ size_t prob = 128);
/**
* Return a 'safe' prime, of the form p=2*q+1 with q prime
@@ -199,7 +203,7 @@ BigInt BOTAN_PUBLIC_API(2,0) random_prime(RandomNumberGenerator& rng,
* @return prime randomly chosen from safe primes of length bits
*/
BigInt BOTAN_PUBLIC_API(2,0) random_safe_prime(RandomNumberGenerator& rng,
- size_t bits);
+ size_t bits);
/**
* Generate DSA parameters using the FIPS 186 kosherizer
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-20 03:49:57 +0000