Package com.babelqueue.gdpr

Class AesGcmCipher

java.lang.Object
com.babelqueue.gdpr.AesGcmCipher
All Implemented Interfaces:
Cipher
public final class AesGcmCipher extends Object implements Cipher
A reference Cipher built ONLY on the JDK's javax.crypto (AES/GCM/NoPadding): AES-GCM authenticated encryption with a fresh random 12-byte IV per call, the IV prepended to the ciphertext, the whole thing Base64-encoded so it drops straight into a JSON string. The key is the CALLER's — this type performs no key management, rotation or derivation; bind a KMS-backed Cipher for that.

A 32-byte key selects AES-256-GCM (recommended); 24- and 16-byte keys select AES-192/128-GCM. GCM authenticates the ciphertext, so decrypt(java.lang.String) rejects any tampered or wrong-key input by throwing (it never returns corrupt plaintext). It pulls no third-party crypto dependency (GR-7) and is safe for concurrent use — javax.crypto.Cipher instances are created per call, and the stored key material is only read.

  • Constructor Summary

    Constructors
    Constructor
    Description
    AesGcmCipher(byte[] keyBytes)
    Build an AES-GCM reference cipher from a raw symmetric key.

  • Method Summary

    Modifier and Type
    Method
    Description
    byte[]
    decrypt(String ciphertext)
    Reverses encrypt(byte[]): Base64-decodes, splits off the prepended IV, and opens the GCM ciphertext.
    String
    encrypt(byte[] plaintext)
    Seals plaintext with a fresh random IV, prepends the IV, and Base64-encodes the result (Base64(iv || ciphertext || tag)).

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • AesGcmCipher

      public AesGcmCipher(byte[] keyBytes)
      Build an AES-GCM reference cipher from a raw symmetric key. The key length selects the AES variant: 32 bytes → AES-256-GCM (recommended), 24 → AES-192, 16 → AES-128.
      Parameters:
      keyBytes - the raw symmetric key (16, 24, or 32 bytes)
      Throws:
      InvalidKeySizeException - if the key is not 16, 24, or 32 bytes

  • Method Details

    • encrypt

      public String encrypt(byte[] plaintext) throws GeneralSecurityException
      Seals plaintext with a fresh random IV, prepends the IV, and Base64-encodes the result (Base64(iv || ciphertext || tag)).
      Specified by:
      encrypt in interface Cipher
      Parameters:
      plaintext - the canonical JSON bytes of one field value
      Returns:
      the ciphertext, encoded so it is safe to place inside a JSON string
      Throws:
      GeneralSecurityException

    • decrypt

      public byte[] decrypt(String ciphertext) throws GeneralSecurityException
      Reverses encrypt(byte[]): Base64-decodes, splits off the prepended IV, and opens the GCM ciphertext. A wrong key or tampered input fails GCM authentication and throws (never corrupt plaintext).
      Specified by:
      decrypt in interface Cipher
      Parameters:
      ciphertext - a string produced by Cipher.encrypt(byte[])
      Returns:
      the original field-value JSON bytes
      Throws:
      MalformedCiphertextException - if the input is not valid Base64 or is too short to hold an IV (i.e. not something this cipher produced)
      GeneralSecurityException - if GCM authentication fails (wrong key or tampering)