add new functionality and improve backend server structure

- Enhance server functionality and optimize backend code
- Add multi-database support (PostgreSQL, MySQL, SQLite)

server/core_backend-server/tools/security/encrypt.go

@@ -0,0 +1,62 @@
+package security
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	crand "crypto/rand"
+	"encoding/base64"
+	"io"
+)
+
+// Encrypt encrypts "data" with the specified "key" (must be valid 32 char AES key).
+//
+// This method uses AES-256-GCM block cypher mode.
+func Encrypt(data []byte, key string) (string, error) {
+	block, err := aes.NewCipher([]byte(key))
+	if err != nil {
+		return "", err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+
+	// populates the nonce with a cryptographically secure random sequence
+	if _, err := io.ReadFull(crand.Reader, nonce); err != nil {
+		return "", err
+	}
+
+	cipherByte := gcm.Seal(nonce, nonce, data, nil)
+
+	result := base64.StdEncoding.EncodeToString(cipherByte)
+
+	return result, nil
+}
+
+// Decrypt decrypts encrypted text with key (must be valid 32 chars AES key).
+//
+// This method uses AES-256-GCM block cypher mode.
+func Decrypt(cipherText string, key string) ([]byte, error) {
+	block, err := aes.NewCipher([]byte(key))
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonceSize := gcm.NonceSize()
+
+	cipherByte, err := base64.StdEncoding.DecodeString(cipherText)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce, cipherByteClean := cipherByte[:nonceSize], cipherByte[nonceSize:]
+	return gcm.Open(nil, nonce, cipherByteClean, nil)
+}