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