Example #1
0
// randomSafePrime returns a number, p, of the given size, such that p and
// (p-1)/2 are both prime with high probability.
func randomSafePrime(rand io.Reader, bits int) (p *big.Int, err os.Error) {
	if bits < 1 {
		err = os.EINVAL
	}

	bytes := make([]byte, (bits+7)/8)
	p = new(big.Int)
	p2 := new(big.Int)

	for {
		_, err = io.ReadFull(rand, bytes)
		if err != nil {
			return
		}

		// Don't let the value be too small.
		bytes[0] |= 0x80
		// Make the value odd since an even number this large certainly isn't prime.
		bytes[len(bytes)-1] |= 1

		p.SetBytes(bytes)
		if big.ProbablyPrime(p, 20) {
			p2.Rsh(p, 1) // p2 = (p - 1)/2
			if big.ProbablyPrime(p2, 20) {
				return
			}
		}
	}

	return
}
Example #2
0
// Prime returns a number, p, of the given size, such that p is prime
// with high probability.
func Prime(rand io.Reader, bits int) (p *big.Int, err error) {
	if bits < 1 {
		err = os.EINVAL
	}

	b := uint(bits % 8)
	if b == 0 {
		b = 8
	}

	bytes := make([]byte, (bits+7)/8)
	p = new(big.Int)

	for {
		_, err = io.ReadFull(rand, bytes)
		if err != nil {
			return nil, err
		}

		// Clear bits in the first byte to make sure the candidate has a size <= bits.
		bytes[0] &= uint8(int(1<<b) - 1)
		// Don't let the value be too small, i.e, set the most significant bit.
		bytes[0] |= 1 << (b - 1)
		// Make the value odd since an even number this large certainly isn't prime.
		bytes[len(bytes)-1] |= 1

		p.SetBytes(bytes)
		if big.ProbablyPrime(p, 20) {
			return
		}
	}

	return
}
Example #3
0
func Euler35() string {
	num := 0
	sieve := primes.FastSieve()
	circularPrimes := make(map[int]int)
	for a := <-sieve; a < 1000000; a = <-sieve {
		_, tested := circularPrimes[a]
		if tested {
			continue
		} else {
			//Test if it's circular
			circular := true
			primesTested := make(map[int]int)
			digits := []byte(strconv.Itoa(a))
			finishedRotations := false
			for ; ; arithmetics.Rotate(digits) {
				number, _ := strconv.Atoi(string(digits))
				_, finishedRotations = primesTested[number]
				if finishedRotations {
					break
				}
				primesTested[number] = 0
				if circular && !big.ProbablyPrime(big.NewInt(int64(number)), 1) {
					circular = false
				}
			}
			for n := range primesTested {
				if circular {
					num += 1
				}
				circularPrimes[n] = 0
			}
		}
	}
	return fmt.Sprint(num)
}
Example #4
0
File: rsa.go Project: richlowe/gcc
func (priv *PrivateKey) Validate() os.Error {
	// Check that p, q and, maybe, r are prime. Note that this is just a
	// sanity check. Since the random witnesses chosen by ProbablyPrime are
	// deterministic, given the candidate number, it's easy for an attack
	// to generate composites that pass this test.
	if !big.ProbablyPrime(priv.P, 20) {
		return os.ErrorString("P is composite")
	}
	if !big.ProbablyPrime(priv.Q, 20) {
		return os.ErrorString("Q is composite")
	}
	if priv.R != nil && !big.ProbablyPrime(priv.R, 20) {
		return os.ErrorString("R is composite")
	}

	// Check that p*q*r == n.
	modulus := new(big.Int).Mul(priv.P, priv.Q)
	if priv.R != nil {
		modulus.Mul(modulus, priv.R)
	}
	if modulus.Cmp(priv.N) != 0 {
		return os.ErrorString("invalid modulus")
	}
	// Check that e and totient(p, q, r) are coprime.
	pminus1 := new(big.Int).Sub(priv.P, bigOne)
	qminus1 := new(big.Int).Sub(priv.Q, bigOne)
	totient := new(big.Int).Mul(pminus1, qminus1)
	if priv.R != nil {
		rminus1 := new(big.Int).Sub(priv.R, bigOne)
		totient.Mul(totient, rminus1)
	}
	e := big.NewInt(int64(priv.E))
	gcd := new(big.Int)
	x := new(big.Int)
	y := new(big.Int)
	big.GcdInt(gcd, x, y, totient, e)
	if gcd.Cmp(bigOne) != 0 {
		return os.ErrorString("invalid public exponent E")
	}
	// Check that de ≡ 1 (mod totient(p, q, r))
	de := new(big.Int).Mul(priv.D, e)
	de.Mod(de, totient)
	if de.Cmp(bigOne) != 0 {
		return os.ErrorString("invalid private exponent D")
	}
	return nil
}
Example #5
0
// Create random numbers until it finds a prime
func create_random_prime(bits int) (prime *big.Int) {
	for true {
		prime = create_random_bignum(bits) // Create a random number
		if big.ProbablyPrime(prime, 20) {  // Do 20 rabin-miller tests to check if it's prime
			return
		}
	}
	return // This is just here to keep the compiler happy
}
Example #6
0
func Euler41() string {
	maxPandigital := "123456789"
	max := 0
	for i := len(maxPandigital); i > 3; i-- {
		pandigital := []byte(maxPandigital[0:i])
		for arithmetics.Permute(pandigital) {
			number, _ := strconv.Atoi(string(pandigital))
			if big.ProbablyPrime(big.NewInt(int64(number)), 1) {
				if number > max {
					max = number
				}
			}
		}
		if max != 0 {
			return fmt.Sprint(max)
		}
	}
	return "Error not prime found"
}
Example #7
0
func (priv *PrivateKey) Validate() os.Error {
	// Check that the prime factors are actually prime. Note that this is
	// just a sanity check. Since the random witnesses chosen by
	// ProbablyPrime are deterministic, given the candidate number, it's
	// easy for an attack to generate composites that pass this test.
	for _, prime := range priv.Primes {
		if !big.ProbablyPrime(prime, 20) {
			return os.ErrorString("Prime factor is composite")
		}
	}

	// Check that Πprimes == n.
	modulus := new(big.Int).Set(bigOne)
	for _, prime := range priv.Primes {
		modulus.Mul(modulus, prime)
	}
	if modulus.Cmp(priv.N) != 0 {
		return os.ErrorString("invalid modulus")
	}
	// Check that e and totient(Πprimes) are coprime.
	totient := new(big.Int).Set(bigOne)
	for _, prime := range priv.Primes {
		pminus1 := new(big.Int).Sub(prime, bigOne)
		totient.Mul(totient, pminus1)
	}
	e := big.NewInt(int64(priv.E))
	gcd := new(big.Int)
	x := new(big.Int)
	y := new(big.Int)
	big.GcdInt(gcd, x, y, totient, e)
	if gcd.Cmp(bigOne) != 0 {
		return os.ErrorString("invalid public exponent E")
	}
	// Check that de ≡ 1 (mod totient(Πprimes))
	de := new(big.Int).Mul(priv.D, e)
	de.Mod(de, totient)
	if de.Cmp(bigOne) != 0 {
		return os.ErrorString("invalid private exponent D")
	}
	return nil
}
Example #8
0
// GenerateParameters puts a random, valid set of DSA parameters into params.
// This function takes many seconds, even on fast machines.
func GenerateParameters(params *Parameters, rand io.Reader, sizes ParameterSizes) (err os.Error) {
	// This function doesn't follow FIPS 186-3 exactly in that it doesn't
	// use a verification seed to generate the primes. The verification
	// seed doesn't appear to be exported or used by other code and
	// omitting it makes the code cleaner.

	var L, N int
	switch sizes {
	case L1024N160:
		L = 1024
		N = 160
	case L2048N224:
		L = 2048
		N = 224
	case L2048N256:
		L = 2048
		N = 256
	case L3072N256:
		L = 3072
		N = 256
	default:
		return os.ErrorString("crypto/dsa: invalid ParameterSizes")
	}

	qBytes := make([]byte, N/8)
	pBytes := make([]byte, L/8)

	q := new(big.Int)
	p := new(big.Int)
	rem := new(big.Int)
	one := new(big.Int)
	one.SetInt64(1)

GeneratePrimes:
	for {
		_, err = io.ReadFull(rand, qBytes)
		if err != nil {
			return
		}

		qBytes[len(qBytes)-1] |= 1
		qBytes[0] |= 0x80
		q.SetBytes(qBytes)

		if !big.ProbablyPrime(q, numMRTests) {
			continue
		}

		for i := 0; i < 4*L; i++ {
			_, err = io.ReadFull(rand, pBytes)
			if err != nil {
				return
			}

			pBytes[len(pBytes)-1] |= 1
			pBytes[0] |= 0x80

			p.SetBytes(pBytes)
			rem.Mod(p, q)
			rem.Sub(rem, one)
			p.Sub(p, rem)
			if p.BitLen() < L {
				continue
			}

			if !big.ProbablyPrime(p, numMRTests) {
				continue
			}

			params.P = p
			params.Q = q
			break GeneratePrimes
		}
	}

	h := new(big.Int)
	h.SetInt64(2)
	g := new(big.Int)

	pm1 := new(big.Int).Sub(p, one)
	e := new(big.Int).Div(pm1, q)

	for {
		g.Exp(h, e, p)
		if g.Cmp(one) == 0 {
			h.Add(h, one)
			continue
		}

		params.G = g
		return
	}

	panic("unreachable")
}