59 lines
1.6 KiB
Go
59 lines
1.6 KiB
Go
package paillier
|
|
|
|
import (
|
|
"crypto/rand"
|
|
"io"
|
|
"math/big"
|
|
"time"
|
|
)
|
|
|
|
var ZERO = big.NewInt(0)
|
|
var ONE = big.NewInt(1)
|
|
var TWO = big.NewInt(2)
|
|
var FOUR = big.NewInt(4)
|
|
|
|
// returns n! = n*(n-1)*(n-2)...3*2*1
|
|
func Factorial(n int) *big.Int {
|
|
ret := big.NewInt(1)
|
|
for i := 1; i <= n; i++ {
|
|
ret = new(big.Int).Mul(ret, big.NewInt(int64(i)))
|
|
}
|
|
return ret
|
|
}
|
|
|
|
// Returns 2 primes such that p = 2 * q + 1 and that the length of
|
|
// p is nbits. `p` is called a safe prime
|
|
//
|
|
// Deprecated: This function has been left here just for backward compatibility.
|
|
// Please use `GenerateSafePrime` from the `safe_prime_generator.go` directly.
|
|
func GenerateSafePrimes(nbits int, random io.Reader) (p, q *big.Int, err error) {
|
|
return GenerateSafePrime(nbits, 4, 120*time.Second)
|
|
}
|
|
|
|
// Generate a random element in the group of all the elements in Z/nZ that
|
|
// has a multiplicative inverse.
|
|
func GetRandomNumberInMultiplicativeGroup(n *big.Int, random io.Reader) (*big.Int, error) {
|
|
r, err := rand.Int(random, n)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
zero := big.NewInt(0)
|
|
one := big.NewInt(1)
|
|
if zero.Cmp(r) == 0 || one.Cmp(new(big.Int).GCD(nil, nil, n, r)) != 0 {
|
|
return GetRandomNumberInMultiplicativeGroup(n, random)
|
|
}
|
|
return r, nil
|
|
|
|
}
|
|
|
|
// Return a random generator of RQn with high probability. THIS METHOD
|
|
// ONLY WORKS IF N IS THE PRODUCT OF TWO SAFE PRIMES! This heuristic is used
|
|
// threshold signature paper in the Victor Shoup
|
|
func GetRandomGeneratorOfTheQuadraticResidue(n *big.Int, rand io.Reader) (*big.Int, error) {
|
|
r, err := GetRandomNumberInMultiplicativeGroup(n, rand)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return new(big.Int).Mod(new(big.Int).Mul(r, r), n), nil
|
|
}
|