feat: add card number encryption utility

docker-compose.yml

@@ -12,6 +12,26 @@ services:
       - "5432:5432"
     volumes:
       - postgres_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+
+  app:
+    build: .
+    container_name: bankcards-app
+    depends_on:
+      postgres:
+        condition: service_healthy
+    ports:
+      - "8080:8080"
+    environment:
+      SPRING_DATASOURCE_URL: jdbc:postgresql://postgres:5432/bankcards
+      SPRING_DATASOURCE_USERNAME: postgres
+      SPRING_DATASOURCE_PASSWORD: postgres
+      APP_JWT_SECRET: 404E635266556A586E3272357538782F413F4428472B4B6250645367566B5970
+      APP_JWT_EXPIRATION: 86400000
 
 volumes:
   postgres_data:

src/main/java/com/example/bankcards/util/CardEncryptionUtil.java

@@ -0,0 +1,56 @@
+package com.example.bankcards.util;
+
+import java.util.Base64;
+import javax.crypto.Cipher;
+import javax.crypto.spec.SecretKeySpec;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+
+@Component
+public class CardEncryptionUtil {
+
+    @Value("${app.card.encryption-key}")
+    private String encryptionKey;
+
+    private static final String ALGORITHM = "AES";
+
+    public String encrypt(String cardNumber) {
+        try {
+            SecretKeySpec keySpec = new SecretKeySpec(
+                encryptionKey.getBytes(),
+                ALGORITHM
+            );
+            Cipher cipher = Cipher.getInstance(ALGORITHM);
+            cipher.init(Cipher.ENCRYPT_MODE, keySpec);
+            byte[] encrypted = cipher.doFinal(cardNumber.getBytes());
+            return Base64.getEncoder().encodeToString(encrypted);
+        } catch (Exception e) {
+            throw new RuntimeException("Failed to encrypt card number", e);
+        }
+    }
+
+    public String decrypt(String encryptedCardNumber) {
+        try {
+            SecretKeySpec keySpec = new SecretKeySpec(
+                encryptionKey.getBytes(),
+                ALGORITHM
+            );
+            Cipher cipher = Cipher.getInstance(ALGORITHM);
+            cipher.init(Cipher.DECRYPT_MODE, keySpec);
+            byte[] decoded = Base64.getDecoder().decode(encryptedCardNumber);
+            byte[] decrypted = cipher.doFinal(decoded);
+            return new String(decrypted);
+        } catch (Exception e) {
+            throw new RuntimeException("Failed to decrypt card number", e);
+        }
+    }
+
+    public String mask(String cardNumber) {
+        if (cardNumber == null || cardNumber.length() < 4) {
+            return "****";
+        }
+        return (
+            "**** **** **** " + cardNumber.substring(cardNumber.length() - 4)
+        );
+    }
+}

src/main/resources/application.yml

@@ -17,3 +17,5 @@ app:
   jwt:
     secret: 404E635266556A586E3272357538782F413F4428472B4B6250645367566B5970
     expiration: 86400000
+  card:
+    encryption-key: 1234567890123456