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crypto/rsa: don't use safe primes.

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Previously we would require safe primes for our RSA key generation.
Since this took rather a long time, this removes the requirement that
the primes be safe.

OpenSSL doesn't use safe primes for RSA key generation either
(openssl-0.9.8l/crypto/rsa/rsa_gen.c:122)

Fixes #649.

R=rsc
CC=golang-dev
https://golang.org/cl/253041
This commit is contained in:
Adam Langley 2010-03-08 09:25:24 -05:00
parent 520621d24c
commit df53544f4f
2 changed files with 7 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
src/pkg/crypto/rsa/rsa.go
View File

@ -18,16 +18,15 @@ import (
var bigZero = big.NewInt(0) var bigZero = big.NewInt(0)
var bigOne = big.NewInt(1) var bigOne = big.NewInt(1)
// randomSafePrime returns a number, p, of the given size, such that p and // randomPrime returns a number, p, of the given size, such that p is prime
// (p-1)/2 are both prime with high probability. // with high probability.
func randomSafePrime(rand io.Reader, bits int) (p *big.Int, err os.Error) { func randomPrime(rand io.Reader, bits int) (p *big.Int, err os.Error) {
if bits < 1 { if bits < 1 {
err = os.EINVAL err = os.EINVAL
} }
bytes := make([]byte, (bits+7)/8) bytes := make([]byte, (bits+7)/8)
p = new(big.Int) p = new(big.Int)
p2 := new(big.Int)
for { for {
_, err = io.ReadFull(rand, bytes) _, err = io.ReadFull(rand, bytes)
@ -42,10 +41,7 @@ func randomSafePrime(rand io.Reader, bits int) (p *big.Int, err os.Error) {
p.SetBytes(bytes) p.SetBytes(bytes)
if big.ProbablyPrime(p, 20) { if big.ProbablyPrime(p, 20) {
p2.Rsh(p, 1) // p2 = (p - 1)/2 return
if big.ProbablyPrime(p2, 20) {
return
}
} }
} }
@ -157,12 +153,12 @@ func GenerateKey(rand io.Reader, bits int) (priv *PrivateKey, err os.Error) {
totient := new(big.Int) totient := new(big.Int)
for { for {
p, err := randomSafePrime(rand, bits/2) p, err := randomPrime(rand, bits/2)
if err != nil { if err != nil {
return nil, err return nil, err
} }
q, err := randomSafePrime(rand, bits/2) q, err := randomPrime(rand, bits/2)
if err != nil { if err != nil {
return nil, err return nil, err
} }

2
src/pkg/crypto/rsa/rsa_test.go
View File

@ -18,7 +18,7 @@ func TestKeyGeneration(t *testing.T) {
t.Errorf("failed to open /dev/urandom") t.Errorf("failed to open /dev/urandom")
} }
priv, err := GenerateKey(urandom, 32) priv, err := GenerateKey(urandom, 1024)
if err != nil { if err != nil {
t.Errorf("failed to generate key") t.Errorf("failed to generate key")
} }