init: v1.0.0

tpc/sm2/sm2m/dec.go

@@ -0,0 +1,89 @@
+package sm2m
+
+import (
+	"crypto/rand"
+	"fmt"
+	"io"
+	"math/big"
+
+	"xdx.jelly/xgcl/gmath"
+	"xdx.jelly/xgcl/sm/sm2"
+)
+
+var (
+	ErrIndataError = fmt.Errorf("data input error")
+)
+
+type ClientDecContext struct {
+	cipher sm2.Cipher
+}
+
+func NewClientDecContext() *ClientDecContext {
+	return &ClientDecContext{cipher: *sm2.NewCipher()}
+}
+
+// Initial 客户端解密，将密文中的C1发送给服务端
+func (c *ClientDecContext) Initial(cipher *sm2.Cipher) (out []byte, err error) {
+	c.cipher.Set(cipher)
+	out = make([]byte, 0, 2*sm2.ByteSize())
+	out = append(out, gmath.BigIntToNByte(cipher.X, sm2.ByteSize())...)
+	out = append(out, gmath.BigIntToNByte(cipher.Y, sm2.ByteSize())...)
+	return out, nil
+}
+
+// Final 客户端解密得到密文
+func (c *ClientDecContext) Final(clientKey *sm2.PrivateKey, in []byte) ([]byte, error) {
+	if len(in) < 2*sm2.ByteSize() {
+		return []byte{}, ErrIndataError
+	}
+	// d*C1 = dc^(-1)*ds^(-1)*C1 - C1
+	x := new(big.Int)
+	x.SetBytes(in[:sm2.ByteSize()])
+	y := new(big.Int)
+	y.SetBytes(in[sm2.ByteSize() : 2*sm2.ByteSize()])
+	cInv := new(big.Int)
+	cInv.Set(clientKey.D)
+	cInv.ModInverse(cInv, sm2.OrderN())
+
+	x, y = sm2.Curve256.ScalarMult(x, y, cInv.Bytes())
+	gx := new(big.Int)
+	gy := new(big.Int)
+	gx.Set(c.cipher.X)
+	gy.Set(c.cipher.Y)
+	gy.Sub(sm2.Prime(), gy)
+	x, y = sm2.Curve().Add(x, y, gx, gy)
+
+	return sm2.Decrypt_aux(x, y, &c.cipher)
+}
+
+func ServerDec(serverKey *sm2.PrivateKey, in []byte) ([]byte, error) {
+	return ServerImportKey(serverKey, in)
+}
+
+// 将加密密钥拆分为服务端和客户端的密钥分量
+func SplitDecryptKey(de *sm2.PrivateKey, rnd io.Reader) (*sm2.PrivateKey, *sm2.PrivateKey, error) {
+	dc := new(big.Int).Add(de.D, gmath.BigInt1)
+	if dc.Cmp(sm2.OrderN()) == 0 {
+		return &sm2.PrivateKey{D: big.NewInt(0)}, &sm2.PrivateKey{D: big.NewInt(0)}, nil
+	}
+
+	var ds *big.Int
+	var err error
+	for {
+		ds, err = rand.Int(rnd, sm2.OrderN())
+		if err != nil {
+			return nil, nil, err
+		}
+		if ds.Sign() > 0 {
+			break
+		}
+	}
+
+	dc.Mul(dc, ds)
+	dc.Mod(dc, sm2.OrderN())
+	dc.ModInverse(dc, sm2.OrderN())
+
+	skc := &sm2.PrivateKey{D: dc}
+	sks := &sm2.PrivateKey{D: ds}
+	return skc, sks, nil
+}