chore: vendor

vendor/github.com/cloudflare/circl/math/primes.go

@@ -0,0 +1,34 @@
+package math
+
+import (
+	"crypto/rand"
+	"io"
+	"math/big"
+)
+
+// IsSafePrime reports whether p is (probably) a safe prime.
+// The prime p=2*q+1 is safe prime if both p and q are primes.
+// Note that ProbablyPrime is not suitable for judging primes
+// that an adversary may have crafted to fool the test.
+func IsSafePrime(p *big.Int) bool {
+	pdiv2 := new(big.Int).Rsh(p, 1)
+	return p.ProbablyPrime(20) && pdiv2.ProbablyPrime(20)
+}
+
+// SafePrime returns a number of the given bit length that is a safe prime with high probability.
+// The number returned p=2*q+1 is a safe prime if both p and q are primes.
+// SafePrime will return error for any error returned by rand.Read or if bits < 2.
+func SafePrime(random io.Reader, bits int) (*big.Int, error) {
+	one := big.NewInt(1)
+	p := new(big.Int)
+	for {
+		q, err := rand.Prime(random, bits-1)
+		if err != nil {
+			return nil, err
+		}
+		p.Lsh(q, 1).Add(p, one)
+		if p.ProbablyPrime(20) {
+			return p, nil
+		}
+	}
+}