diff --git a/crypto.go b/crypto.go
new file mode 100644
index 0000000..6c66e1d
--- /dev/null
+++ b/crypto.go
@@ -0,0 +1,142 @@
+package xyshanghai
+
+import (
+	"crypto/cipher"
+	"encoding/base64"
+	"encoding/hex"
+	"fmt"
+
+	"github.com/tjfoc/gmsm/sm3"
+	"github.com/tjfoc/gmsm/sm4"
+)
+
+// SM4Encrypt 使用SM4 ECB模式加密数据，返回base64编码字符串
+func SM4Encrypt(key, plaintext []byte) (string, error) {
+	block, err := sm4.NewCipher(key)
+	if err != nil {
+		return "", fmt.Errorf("sm4 new cipher: %w", err)
+	}
+
+	// PKCS7填充
+	plaintext = pkcs7Padding(plaintext, block.BlockSize())
+
+	// ECB模式
+	mode := newECBEncrypter(block)
+	ciphertext := make([]byte, len(plaintext))
+	mode.CryptBlocks(ciphertext, plaintext)
+
+	return base64.StdEncoding.EncodeToString(ciphertext), nil
+}
+
+// SM4Decrypt 解密base64编码的SM4 ECB密文，返回明文
+func SM4Decrypt(key []byte, ciphertextBase64 string) ([]byte, error) {
+	ciphertext, err := base64.StdEncoding.DecodeString(ciphertextBase64)
+	if err != nil {
+		return nil, fmt.Errorf("base64 decode: %w", err)
+	}
+
+	block, err := sm4.NewCipher(key)
+	if err != nil {
+		return nil, fmt.Errorf("sm4 new cipher: %w", err)
+	}
+
+	mode := newECBDecrypter(block)
+	plaintext := make([]byte, len(ciphertext))
+	mode.CryptBlocks(plaintext, ciphertext)
+
+	// 去除PKCS7填充
+	plaintext, err = pkcs7Unpadding(plaintext, block.BlockSize())
+	if err != nil {
+		return nil, fmt.Errorf("pkcs7 unpadding: %w", err)
+	}
+
+	return plaintext, nil
+}
+
+// SM3Sign 使用SM3加盐签名，返回十六进制字符串
+func SM3Sign(salt []byte, data string) string {
+	h := sm3.Sm3WithSalt(salt)
+	h.Write([]byte(data))
+	return hex.EncodeToString(h.Sum(nil))
+}
+
+// pkcs7Padding PKCS7填充
+func pkcs7Padding(src []byte, blockSize int) []byte {
+	padding := blockSize - len(src)%blockSize
+	padtext := make([]byte, padding)
+	for i := range padtext {
+		padtext[i] = byte(padding)
+	}
+	return append(src, padtext...)
+}
+
+// pkcs7Unpadding 去除PKCS7填充
+func pkcs7Unpadding(src []byte, blockSize int) ([]byte, error) {
+	length := len(src)
+	if length == 0 {
+		return nil, fmt.Errorf("empty data")
+	}
+	unpadding := int(src[length-1])
+	if unpadding > blockSize || unpadding == 0 {
+		return nil, fmt.Errorf("invalid padding")
+	}
+	for i := length - unpadding; i < length; i++ {
+		if src[i] != byte(unpadding) {
+			return nil, fmt.Errorf("invalid padding")
+		}
+	}
+	return src[:length-unpadding], nil
+}
+
+// ecb 实现ECB模式（标准库未提供）
+type ecb struct {
+	b         cipher.Block
+	blockSize int
+}
+
+func newECB(b cipher.Block) *ecb {
+	return &ecb{
+		b:         b,
+		blockSize: b.BlockSize(),
+	}
+}
+
+type ecbEncrypter ecb
+
+func newECBEncrypter(b cipher.Block) cipher.BlockMode {
+	return (*ecbEncrypter)(newECB(b))
+}
+
+func (x *ecbEncrypter) BlockSize() int { return x.blockSize }
+
+func (x *ecbEncrypter) CryptBlocks(dst, src []byte) {
+	if len(src)%x.blockSize != 0 {
+		panic("crypto/cipher: input not full blocks")
+	}
+	if len(dst) < len(src) {
+		panic("crypto/cipher: output smaller than input")
+	}
+	for i := 0; i < len(src); i += x.blockSize {
+		x.b.Encrypt(dst[i:i+x.blockSize], src[i:i+x.blockSize])
+	}
+}
+
+type ecbDecrypter ecb
+
+func newECBDecrypter(b cipher.Block) cipher.BlockMode {
+	return (*ecbDecrypter)(newECB(b))
+}
+
+func (x *ecbDecrypter) BlockSize() int { return x.blockSize }
+
+func (x *ecbDecrypter) CryptBlocks(dst, src []byte) {
+	if len(src)%x.blockSize != 0 {
+		panic("crypto/cipher: input not full blocks")
+	}
+	if len(dst) < len(src) {
+		panic("crypto/cipher: output smaller than input")
+	}
+	for i := 0; i < len(src); i += x.blockSize {
+		x.b.Decrypt(dst[i:i+x.blockSize], src[i:i+x.blockSize])
+	}
+}
\ No newline at end of file