Class Cipher

java.lang.Object
com.codename1.security.Cipher
public final class Cipher extends Object

Convenience entry points for symmetric (AES) and asymmetric (RSA) encryption. The actual algorithms run on the platform's native crypto provider -- this class is just a thin, friendly facade over the CodenameOneImplementation crypto bridge.

  • AES: AES/GCM/NoPadding for authenticated encryption (uses a 12-byte nonce and produces ciphertext with a 16-byte tag appended). Falls back to AES/CBC/PKCS5Padding if GCM is unavailable on a target platform.
  • RSA: RSA/ECB/OAEPWithSHA-256AndMGF1Padding for new code, RSA/ECB/PKCS1Padding only for interop with old systems.
Example: AES-GCM round-trip
SecretKey key = KeyGenerator.aes(256);
byte[] nonce  = SecureRandom.bytes(12);
byte[] cipher = Cipher.aesEncrypt(Cipher.AES_GCM, key, nonce, null, "secret".getBytes("UTF-8"));
byte[] plain  = Cipher.aesDecrypt(Cipher.AES_GCM, key, nonce, null, cipher);
Example: RSA-OAEP round-trip
KeyPair kp = KeyGenerator.rsa(2048);
byte[] cipher = Cipher.rsaEncrypt(Cipher.RSA_OAEP_SHA256, kp.getPublicKey(), data);
byte[] plain  = Cipher.rsaDecrypt(Cipher.RSA_OAEP_SHA256, kp.getPrivateKey(), cipher);

  • Field Details

    • AES_GCM

      public static final String AES_GCM
      AES/GCM/NoPadding -- recommended authenticated mode for AES.
      See Also:

    • AES_CBC_PKCS5

      public static final String AES_CBC_PKCS5
      AES/CBC/PKCS5Padding -- block-chained AES with PKCS#5 padding.
      See Also:

    • AES_CBC

      public static final String AES_CBC
      AES/CBC/NoPadding -- raw CBC, caller must pre-pad to a 16-byte boundary.
      See Also:

    • AES_ECB_PKCS5

      public static final String AES_ECB_PKCS5
      AES/ECB/PKCS5Padding -- legacy interop only. ECB leaks structure; avoid for new designs.
      See Also:

    • RSA_OAEP_SHA256

      public static final String RSA_OAEP_SHA256

      RSA/ECB/OAEPWithSHA-256AndMGF1Padding -- recommended RSA encryption transformation.

      SHA-256 is used for the label hash and for MGF1. That is worth stating because the JCE reading of this name leaves MGF1 on SHA-1, and this API deliberately does not: Web Crypto's RSA-OAEP takes a single hash and applies it to both, as does Apple's SecKey, so the split pairing is not expressible on the JavaScript or iOS ports at all. SHA-256 for both is the only choice every port can produce, so it is the one that lets ciphertext cross between them. The JavaSE and Android ports pass an explicit OAEPParameterSpec rather than inheriting their provider's default.

      Interoperating with an external system that uses the JCE default (SHA-1 MGF1) therefore needs that system to name SHA-256 for the mask as well.

      See Also:

    • RSA_PKCS1

      public static final String RSA_PKCS1
      RSA/ECB/PKCS1Padding -- legacy RSA padding, kept for interop.
      See Also:

  • Method Details

    • aesEncrypt

      public static byte[] aesEncrypt(String transformation, SecretKey key, byte[] iv, byte[] aad, byte[] plaintext)

      Encrypts with AES.

      Parameters

      • transformation: one of AES_GCM, AES_CBC_PKCS5, AES_CBC, AES_ECB_PKCS5

      • key: AES key (16, 24 or 32 bytes for AES-128/192/256)

      • iv: initialisation vector for CBC (16 bytes) / nonce for GCM (12 bytes recommended). Pass null for ECB.

      • aad: associated authenticated data -- GCM only, may be null

      • plaintext: data to encrypt

    • aesDecrypt

      public static byte[] aesDecrypt(String transformation, SecretKey key, byte[] iv, byte[] aad, byte[] ciphertext)
      Decrypts AES ciphertext produced by aesEncrypt(String, SecretKey, byte[], byte[], byte[]). For GCM mode, the auth tag is part of the ciphertext (last 16 bytes) -- a tag mismatch raises CryptoException.

    • rsaEncrypt

      public static byte[] rsaEncrypt(String transformation, PublicKey key, byte[] plaintext)
      Encrypts a small amount of data with RSA. The plaintext size is bounded by the modulus minus padding overhead (e.g. ~190 bytes max for RSA-2048 + OAEP-SHA-256); use AES with an RSA-wrapped AES key for larger payloads.

    • rsaDecrypt

      public static byte[] rsaDecrypt(String transformation, PrivateKey key, byte[] ciphertext)
      Decrypts an RSA ciphertext.