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crypto/dsa: add support for DSA
R=bradfitzgo, r, bradfitzwork, nsz, rsc CC=golang-dev https://golang.org/cl/3990043
This commit is contained in:
Adam Langley
parent
d0e6c7e134
commit
166008b988
@ -33,6 +33,7 @@ DIRS=\
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crypto/blowfish\
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crypto/cast5\
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crypto/cipher\
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crypto/dsa\
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crypto/elliptic\
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crypto/hmac\
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crypto/md4\
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11
src/pkg/crypto/dsa/Makefile
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11
src/pkg/crypto/dsa/Makefile
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@ -0,0 +1,11 @@
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# Copyright 2011 The Go Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style
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# license that can be found in the LICENSE file.
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include ../../../Make.inc
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TARG=crypto/dsa
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GOFILES=\
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dsa.go\
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include ../../../Make.pkg
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276
src/pkg/crypto/dsa/dsa.go
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276
src/pkg/crypto/dsa/dsa.go
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@ -0,0 +1,276 @@
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// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package dsa implements the Digital Signature Algorithm, as defined in FIPS 186-3
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package dsa
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import (
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"big"
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"io"
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"os"
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)
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// Parameters represents the domain parameters for a key. These parameters can
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// be shared across many keys. The bit length of Q must be a multiple of 8.
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type Parameters struct {
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P, Q, G *big.Int
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}
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// PublicKey represents a DSA public key.
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type PublicKey struct {
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Parameters
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Y *big.Int
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}
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// PrivateKey represents a DSA private key.
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type PrivateKey struct {
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PublicKey
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X *big.Int
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}
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type invalidPublicKeyError int
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func (invalidPublicKeyError) String() string {
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return "crypto/dsa: invalid public key"
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}
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// InvalidPublicKeyError results when a public key is not usable by this code.
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// FIPS is quite strict about the format of DSA keys, but other code may be
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// less so. Thus, when using keys which may have been generated by other code,
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// this error must be handled.
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var InvalidPublicKeyError = invalidPublicKeyError(0)
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// ParameterSizes is a enumeration of the acceptable bit lengths of the primes
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// in a set of DSA parameters. See FIPS 186-3, section 4.2.
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type ParameterSizes int
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const (
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L1024N160 ParameterSizes = iota
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L2048N224
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L2048N256
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L3072N256
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)
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// numMRTests is the number of Miller-Rabin primality tests that we perform. We
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// pick the largest recommended number from table C.1 of FIPS 186-3.
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const numMRTests = 64
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// GenerateParameters puts a random, valid set of DSA parameters into params.
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// This function takes many seconds, even on fast machines.
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func GenerateParameters(params *Parameters, rand io.Reader, sizes ParameterSizes) (err os.Error) {
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// This function doesn't follow FIPS 186-3 exactly in that it doesn't
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// use a verification seed to generate the primes. The verification
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// seed doesn't appear to be exported or used by other code and
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// omitting it makes the code cleaner.
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var L, N int
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switch sizes {
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case L1024N160:
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L = 1024
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N = 160
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case L2048N224:
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L = 2048
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N = 224
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case L2048N256:
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L = 2048
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N = 256
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case L3072N256:
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L = 3072
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N = 256
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default:
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return os.ErrorString("crypto/dsa: invalid ParameterSizes")
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}
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qBytes := make([]byte, N/8)
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pBytes := make([]byte, L/8)
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q := new(big.Int)
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p := new(big.Int)
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rem := new(big.Int)
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one := new(big.Int)
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one.SetInt64(1)
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GeneratePrimes:
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for {
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_, err = io.ReadFull(rand, qBytes)
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if err != nil {
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return
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}
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qBytes[len(qBytes)-1] |= 1
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qBytes[0] |= 0x80
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q.SetBytes(qBytes)
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if !big.ProbablyPrime(q, numMRTests) {
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continue
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}
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for i := 0; i < 4*L; i++ {
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_, err = io.ReadFull(rand, pBytes)
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if err != nil {
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return
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}
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pBytes[len(pBytes)-1] |= 1
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pBytes[0] |= 0x80
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p.SetBytes(pBytes)
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rem.Mod(p, q)
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rem.Sub(rem, one)
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p.Sub(p, rem)
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if p.BitLen() < L {
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continue
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}
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if !big.ProbablyPrime(p, numMRTests) {
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continue
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}
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params.P = p
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params.Q = q
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break GeneratePrimes
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}
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}
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h := new(big.Int)
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h.SetInt64(2)
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g := new(big.Int)
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pm1 := new(big.Int).Sub(p, one)
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e := new(big.Int).Div(pm1, q)
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for {
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g.Exp(h, e, p)
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if g.Cmp(one) == 0 {
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h.Add(h, one)
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continue
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}
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params.G = g
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return
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}
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panic("unreachable")
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}
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// GenerateKey generates a public&private key pair. The Parameters of the
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// PrivateKey must already be valid (see GenerateParameters).
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func GenerateKey(priv *PrivateKey, rand io.Reader) os.Error {
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if priv.P == nil || priv.Q == nil || priv.G == nil {
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return os.ErrorString("crypto/dsa: parameters not set up before generating key")
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}
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x := new(big.Int)
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xBytes := make([]byte, priv.Q.BitLen()/8)
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for {
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_, err := io.ReadFull(rand, xBytes)
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if err != nil {
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return err
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}
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x.SetBytes(xBytes)
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if x.Sign() != 0 && x.Cmp(priv.Q) < 0 {
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break
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}
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}
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priv.X = x
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priv.Y = new(big.Int)
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priv.Y.Exp(priv.G, x, priv.P)
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return nil
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}
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// Sign signs an arbitrary length hash (which should be the result of hashing a
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// larger message) using the private key, priv. It returns the signature as a
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// pair of integers. The security of the private key depends on the entropy of
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// rand.
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func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err os.Error) {
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// FIPS 186-3, section 4.6
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n := priv.Q.BitLen()
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if n&7 != 0 {
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err = InvalidPublicKeyError
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return
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}
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n >>= 3
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for {
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k := new(big.Int)
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buf := make([]byte, n)
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for {
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_, err = io.ReadFull(rand, buf)
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if err != nil {
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return
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}
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k.SetBytes(buf)
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if k.Sign() > 0 && k.Cmp(priv.Q) < 0 {
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break
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}
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}
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kInv := new(big.Int).ModInverse(k, priv.Q)
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r = new(big.Int).Exp(priv.G, k, priv.P)
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r.Mod(r, priv.Q)
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if r.Sign() == 0 {
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continue
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}
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if n > len(hash) {
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n = len(hash)
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}
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z := k.SetBytes(hash[:n])
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s = new(big.Int).Mul(priv.X, r)
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s.Add(s, z)
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s.Mod(s, priv.Q)
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s.Mul(s, kInv)
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s.Mod(s, priv.Q)
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if s.Sign() != 0 {
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break
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}
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}
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return
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}
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// Verify verifies the signature in r, s of hash using the public key, pub. It
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// returns true iff the signature is valid.
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func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool {
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// FIPS 186-3, section 4.7
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if r.Sign() < 1 || r.Cmp(pub.Q) >= 0 {
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return false
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}
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if s.Sign() < 1 || s.Cmp(pub.Q) >= 0 {
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return false
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}
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w := new(big.Int).ModInverse(s, pub.Q)
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n := pub.Q.BitLen()
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if n&7 != 0 {
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return false
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}
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n >>= 3
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if n > len(hash) {
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n = len(hash)
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}
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z := new(big.Int).SetBytes(hash[:n])
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u1 := new(big.Int).Mul(z, w)
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u1.Mod(u1, pub.Q)
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u2 := w.Mul(r, w)
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u2.Mod(u2, pub.Q)
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v := u1.Exp(pub.G, u1, pub.P)
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u2.Exp(pub.Y, u2, pub.P)
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v.Mul(v, u2)
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v.Mod(v, pub.P)
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v.Mod(v, pub.Q)
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return v.Cmp(r) == 0
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}
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84
src/pkg/crypto/dsa/dsa_test.go
Normal file
84
src/pkg/crypto/dsa/dsa_test.go
Normal file
@ -0,0 +1,84 @@
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// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package dsa
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import (
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"big"
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"crypto/rand"
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"testing"
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)
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func testSignAndVerify(t *testing.T, i int, priv *PrivateKey) {
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hashed := []byte("testing")
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r, s, err := Sign(rand.Reader, priv, hashed)
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if err != nil {
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t.Errorf("%d: error signing: %s", i, err)
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return
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}
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if !Verify(&priv.PublicKey, hashed, r, s) {
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t.Errorf("%d: Verify failed", i)
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}
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}
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func testParameterGeneration(t *testing.T, sizes ParameterSizes, L, N int) {
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var priv PrivateKey
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params := &priv.Parameters
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err := GenerateParameters(params, rand.Reader, sizes)
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if err != nil {
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t.Errorf("%d: %s", int(sizes), err)
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return
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}
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if params.P.BitLen() != L {
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t.Errorf("%d: params.BitLen got:%d want:%d", int(sizes), params.P.BitLen(), L)
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}
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if params.Q.BitLen() != N {
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t.Errorf("%d: q.BitLen got:%d want:%d", int(sizes), params.Q.BitLen(), L)
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}
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one := new(big.Int)
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one.SetInt64(1)
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pm1 := new(big.Int).Sub(params.P, one)
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quo, rem := new(big.Int).DivMod(pm1, params.Q, new(big.Int))
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if rem.Sign() != 0 {
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t.Errorf("%d: p-1 mod q != 0", int(sizes))
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}
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x := new(big.Int).Exp(params.G, quo, params.P)
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if x.Cmp(one) == 0 {
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t.Errorf("%d: invalid generator", int(sizes))
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}
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err = GenerateKey(&priv, rand.Reader)
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if err != nil {
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t.Errorf("error generating key: %s", err)
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return
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}
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testSignAndVerify(t, int(sizes), &priv)
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}
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func TestParameterGeneration(t *testing.T) {
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// This test is too slow to run all the time.
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return
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testParameterGeneration(t, L1024N160, 1024, 160)
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testParameterGeneration(t, L2048N224, 2048, 224)
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testParameterGeneration(t, L2048N256, 2048, 256)
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testParameterGeneration(t, L3072N256, 3072, 256)
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}
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func TestSignAndVerify(t *testing.T) {
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var priv PrivateKey
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priv.P, _ = new(big.Int).SetString("A9B5B793FB4785793D246BAE77E8FF63CA52F442DA763C440259919FE1BC1D6065A9350637A04F75A2F039401D49F08E066C4D275A5A65DA5684BC563C14289D7AB8A67163BFBF79D85972619AD2CFF55AB0EE77A9002B0EF96293BDD0F42685EBB2C66C327079F6C98000FBCB79AACDE1BC6F9D5C7B1A97E3D9D54ED7951FEF", 16)
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priv.Q, _ = new(big.Int).SetString("E1D3391245933D68A0714ED34BBCB7A1F422B9C1", 16)
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priv.G, _ = new(big.Int).SetString("634364FC25248933D01D1993ECABD0657CC0CB2CEED7ED2E3E8AECDFCDC4A25C3B15E9E3B163ACA2984B5539181F3EFF1A5E8903D71D5B95DA4F27202B77D2C44B430BB53741A8D59A8F86887525C9F2A6A5980A195EAA7F2FF910064301DEF89D3AA213E1FAC7768D89365318E370AF54A112EFBA9246D9158386BA1B4EEFDA", 16)
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priv.Y, _ = new(big.Int).SetString("32969E5780CFE1C849A1C276D7AEB4F38A23B591739AA2FE197349AEEBD31366AEE5EB7E6C6DDB7C57D02432B30DB5AA66D9884299FAA72568944E4EEDC92EA3FBC6F39F53412FBCC563208F7C15B737AC8910DBC2D9C9B8C001E72FDC40EB694AB1F06A5A2DBD18D9E36C66F31F566742F11EC0A52E9F7B89355C02FB5D32D2", 16)
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priv.X, _ = new(big.Int).SetString("5078D4D29795CBE76D3AACFE48C9AF0BCDBEE91A", 16)
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testSignAndVerify(t, 0, &priv)
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}
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