first commit

clientsdk/cecdh/ecdh.go

@@ -0,0 +1,81 @@
+package cecdh
+
+import (
+	"crypto"
+	"crypto/elliptic"
+	"io"
+	"math/big"
+)
+
+// ECDH 秘钥交换算法的主接口
+type ECDH interface {
+	GenerateKey(io.Reader) ([]byte, []byte, error)
+	Marshal(crypto.PublicKey) []byte
+	Unmarshal([]byte) (crypto.PublicKey, bool)
+	GenerateSharedSecret([]byte, crypto.PublicKey) ([]byte, error)
+}
+
+type ellipticECDH struct {
+	ECDH
+	curve elliptic.Curve
+}
+
+type ellipticPublicKey struct {
+	elliptic.Curve
+	X, Y *big.Int
+}
+
+// NewEllipticECDH 指定一种椭圆曲线算法用于创建一个ECDH的实例
+// 关于椭圆曲线算法标准库里面实现了4种: 见crypto/elliptic
+func NewEllipticECDH(curve elliptic.Curve) ECDH {
+	return &ellipticECDH{
+		curve: curve,
+	}
+}
+
+// GenerateKey 基于标准库的NIST椭圆曲线算法生成秘钥对
+func (e *ellipticECDH) GenerateKey(rand io.Reader) ([]byte, []byte, error) {
+	var d []byte
+	var x, y *big.Int
+	var pub *ellipticPublicKey
+	var err error
+	d, x, y, err = elliptic.GenerateKey(e.curve, rand)
+	if err != nil {
+		return nil, nil, err
+	}
+	pub = &ellipticPublicKey{
+		Curve: e.curve,
+		X:     x,
+		Y:     y,
+	}
+	return d, e.Marshal(pub), nil
+}
+
+// Marshal用于公钥的序列化
+func (e *ellipticECDH) Marshal(p crypto.PublicKey) []byte {
+	pub := p.(*ellipticPublicKey)
+	return elliptic.Marshal(e.curve, pub.X, pub.Y)
+}
+
+// Unmarshal用于公钥的反序列化
+func (e *ellipticECDH) Unmarshal(data []byte) (crypto.PublicKey, bool) {
+	var key *ellipticPublicKey
+	var x, y *big.Int
+	x, y = elliptic.Unmarshal(e.curve, data)
+	if x == nil || y == nil {
+		return key, false
+	}
+	key = &ellipticPublicKey{
+		Curve: e.curve,
+		X:     x,
+		Y:     y,
+	}
+	return key, true
+}
+
+// GenerateSharedSecret 通过自己的私钥和对方的公钥协商一个共享密码
+func (e *ellipticECDH) GenerateSharedSecret(privKey []byte, pubKey crypto.PublicKey) ([]byte, error) {
+	pub := pubKey.(*ellipticPublicKey)
+	x, _ := e.curve.ScalarMult(pub.X, pub.Y, privKey)
+	return x.Bytes(), nil
+}