feat: add Go backend compatibility service scaffold

go-backend/internal/security/aes.go

@@ -0,0 +1,65 @@
+package security
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+)
+
+type AESCrypto struct {
+	key []byte
+}
+
+func NewAESCrypto(secret string) (*AESCrypto, error) {
+	if secret == "" {
+		return nil, fmt.Errorf("secret is empty")
+	}
+	hash := sha256.Sum256([]byte(secret))
+	return &AESCrypto{key: hash[:]}, nil
+}
+
+func (a *AESCrypto) Encrypt(plain []byte) (string, error) {
+	if len(plain) == 0 {
+		return "", fmt.Errorf("empty plaintext")
+	}
+	block, err := aes.NewCipher(a.key)
+	if err != nil {
+		return "", err
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", err
+	}
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := rand.Read(nonce); err != nil {
+		return "", err
+	}
+	sealed := gcm.Seal(nil, nonce, plain, nil)
+	data := append(nonce, sealed...)
+	return base64.StdEncoding.EncodeToString(data), nil
+}
+
+func (a *AESCrypto) Decrypt(cipherText string) ([]byte, error) {
+	raw, err := base64.StdEncoding.DecodeString(cipherText)
+	if err != nil {
+		return nil, err
+	}
+	block, err := aes.NewCipher(a.key)
+	if err != nil {
+		return nil, err
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+	nonceSize := gcm.NonceSize()
+	if len(raw) < nonceSize {
+		return nil, fmt.Errorf("ciphertext too short")
+	}
+	nonce := raw[:nonceSize]
+	data := raw[nonceSize:]
+	return gcm.Open(nil, nonce, data, nil)
+}

go-backend/internal/security/md5.go

@@ -0,0 +1,11 @@
+package security
+
+import (
+	"crypto/md5"
+	"fmt"
+)
+
+func MD5(input string) string {
+	hash := md5.Sum([]byte(input))
+	return fmt.Sprintf("%x", hash)
+}