AES 대칭 암호화

대칭 암호화와 비대칭 암호화

AES 모드: CBC와 GCM

AES 키 생성

KeyGenerator kg = KeyGenerator.getInstance("AES");
kg.init(256); // 256-bit key
SecretKey key = kg.generateKey();
// Persist the key:
String b64Key = Base64.getEncoder().encodeToString(key.getEncoded());
// Restore the key:
byte[] decoded = Base64.getDecoder().decode(b64Key);
SecretKey restored = new SecretKeySpec(decoded, "AES");

AES/GCM 암호화

byte[] iv = new byte[12]; // 96-bit IV for GCM
new SecureRandom().nextBytes(iv);
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
GCMParameterSpec spec = new GCMParameterSpec(128, iv); // 128-bit auth tag
cipher.init(Cipher.ENCRYPT_MODE, key, spec);
byte[] ciphertext = cipher.doFinal(plaintext.getBytes(StandardCharsets.UTF_8));
// Transmit/store: IV + ciphertext (IV is not secret)

AES/GCM 복호화

// Assume stored = iv + ciphertext:
byte[] iv         = Arrays.copyOfRange(stored, 0, 12);
byte[] ciphertext = Arrays.copyOfRange(stored, 12, stored.length);
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
cipher.init(Cipher.DECRYPT_MODE, key, new GCMParameterSpec(128, iv));
byte[] plaintext = cipher.doFinal(ciphertext); // throws if tampered

암호문과 함께 IV 저장하기

byte[] encryptedData = new byte[iv.length + ciphertext.length];
System.arraycopy(iv,         0, encryptedData, 0,          iv.length);
System.arraycopy(ciphertext, 0, encryptedData, iv.length, ciphertext.length);
String b64 = Base64.getEncoder().encodeToString(encryptedData);

비밀번호에서 키 파생하기(PBKDF2)

PBEKeySpec spec = new PBEKeySpec(password.toCharArray(), salt, 310_000, 256);
SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
byte[] keyBytes = skf.generateSecret(spec).getEncoded();
SecretKey key = new SecretKeySpec(keyBytes, "AES");

Java 보안 공급자 사용

// With Bouncy Castle:
Security.addProvider(new BouncyCastleProvider());
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");

봉투 암호화 패턴

Spring 애플리케이션에서 AES 사용하기

TextEncryptor encryptor = Encryptors.text(password, salt);
String encrypted = encryptor.encrypt("sensitive data");
String decrypted = encryptor.decrypt(encrypted);

일반적인 주의 사항

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