Fixed some issues, and made things readible from File.

src/main/java/me/zacharias/bank/Utils.java

@@ -0,0 +1,133 @@
+package me.zacharias.bank;
+
+import javax.crypto.Cipher;
+import javax.crypto.SecretKey;
+import javax.crypto.SecretKeyFactory;
+import javax.crypto.spec.GCMParameterSpec;
+import javax.crypto.spec.PBEKeySpec;
+import javax.crypto.spec.SecretKeySpec;
+import java.io.*;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.util.Base64;
+
+public class Utils {
+    public static String SHA256(String input) {
+        MessageDigest sha256 = null;
+        try {
+            sha256 = MessageDigest.getInstance("SHA-256");
+        } catch (NoSuchAlgorithmException e) {
+            throw new RuntimeException(e);
+        }
+        byte[] hash = sha256.digest(input.getBytes(StandardCharsets.UTF_8));
+
+        StringBuilder hexString = new StringBuilder();
+        for (byte b : hash) {
+            String hex = Integer.toHexString(0xff & b);
+            if (hex.length() == 1) hexString.append('0');
+            hexString.append(hex);
+        }
+
+        return hexString.toString();
+    }
+
+    private static final int KEY_SIZE = 256;
+    private static final int ITERATIONS = 65536;
+    private static final int SALT_LENGTH = 16;
+    private static final int IV_LENGTH = 12;
+
+    public static String Encrypt(String data, String username) throws Exception {
+        SecureRandom random = new SecureRandom();
+
+        byte[] salt = new byte[SALT_LENGTH];
+        random.nextBytes(salt);
+
+        byte[] iv = new byte[IV_LENGTH];
+        random.nextBytes(iv);
+
+        SecretKey key = deriveKey(username, salt);
+
+        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
+        GCMParameterSpec gcmSpec = new GCMParameterSpec(128, iv);
+        cipher.init(Cipher.ENCRYPT_MODE, key, gcmSpec);
+        byte[] encryptedData = cipher.doFinal(data.getBytes());
+
+        byte[] combined = new byte[salt.length + iv.length + encryptedData.length];
+        System.arraycopy(salt, 0, combined, 0, salt.length);
+        System.arraycopy(iv, 0, combined, salt.length, iv.length);
+        System.arraycopy(encryptedData, 0, combined, salt.length + iv.length, encryptedData.length);
+
+        return Base64.getEncoder().encodeToString(combined);
+    }
+
+    public static String Decrypt(String data, String username) throws Exception {
+        byte[] combined = Base64.getDecoder().decode(data);
+
+        // Extract salt, IV, and encrypted data
+        byte[] salt = new byte[SALT_LENGTH];
+        byte[] iv = new byte[IV_LENGTH];
+        byte[] cipherText = new byte[combined.length - SALT_LENGTH - IV_LENGTH];
+
+        System.arraycopy(combined, 0, salt, 0, salt.length);
+        System.arraycopy(combined, salt.length, iv, 0, iv.length);
+        System.arraycopy(combined, salt.length + iv.length, cipherText, 0, cipherText.length);
+
+        SecretKey key = deriveKey(username, salt);
+
+        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
+        GCMParameterSpec gcmSpec = new GCMParameterSpec(128, iv);
+        cipher.init(Cipher.DECRYPT_MODE, key, gcmSpec);
+        byte[] decrptedData = cipher.doFinal(cipherText);
+
+        return new String(decrptedData);
+    }
+
+    private static SecretKey deriveKey(String password, byte[] salt) throws Exception {
+        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
+        PBEKeySpec spec = new PBEKeySpec(password.toCharArray(), salt, ITERATIONS, KEY_SIZE);
+        return new SecretKeySpec(factory.generateSecret(spec).getEncoded(), "AES");
+    }
+
+    public static String ReadFile(File file)
+    {
+        if(!file.exists())
+        {
+            throw new RuntimeException(new FileNotFoundException(file.getPath()+" not found"));
+        }
+
+        try {
+            BufferedReader br = new BufferedReader(new FileReader(file));
+            StringBuilder sb = new StringBuilder();
+            String line;
+            while((line = br.readLine()) != null)
+            {
+                sb.append(line);
+            }
+            return sb.toString();
+        }
+        catch (IOException e)
+        {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static void WriteFile(File file, String data) {
+        if(file.exists())
+        {
+            file.delete();
+        }
+
+        try {
+            file.createNewFile();
+
+            BufferedWriter bw = new BufferedWriter(new FileWriter(file));
+            bw.write(data);
+            bw.close();
+        }catch (IOException e)
+        {
+            throw new RuntimeException(e);
+        }
+    }
+}