public final class Cipher

Object
Cipher

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.

Recommended transformations

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);

Fields

`public static final` `String AES_GCM = "AES/GCM/NoPadding"`	`AES/GCM/NoPadding` – recommended authenticated mode for AES.
`public static final` `String AES_CBC_PKCS5 = "AES/CBC/PKCS5Padding"`	`AES/CBC/PKCS5Padding` – block-chained AES with PKCS#5 padding.
`public static final` `String AES_CBC = "AES/CBC/NoPadding"`	`AES/CBC/NoPadding` – raw CBC, caller must pre-pad to a 16-byte boundary.
`public static final` `String AES_ECB_PKCS5 = "AES/ECB/PKCS5Padding"`	`AES/ECB/PKCS5Padding` – legacy interop only.
`public static final` `String RSA_OAEP_SHA256 = "RSA/ECB/OAEPWithSHA-256AndMGF1Padding"`	`RSA/ECB/OAEPWithSHA-256AndMGF1Padding` – recommended RSA encryption transformation.
`public static final` `String RSA_PKCS1 = "RSA/ECB/PKCS1Padding"`	`RSA/ECB/PKCS1Padding` – legacy RSA padding, kept for interop.

Methods

`public static byte[] aesEncrypt(String transformation, SecretKey key, byte[] iv, byte[] aad, byte[] plaintext)`	Encrypts with AES.
`public static byte[] aesDecrypt(String transformation, SecretKey key, byte[] iv, byte[] aad, byte[] ciphertext)`	Decrypts AES ciphertext produced by `aesEncrypt`.
`public static byte[] rsaEncrypt(String transformation, PublicKey key, byte[] plaintext)`	Encrypts a small amount of data with RSA.
`public static byte[] rsaDecrypt(String transformation, PrivateKey key, byte[] ciphertext)`	Decrypts an RSA ciphertext.

Inherited methods

From Object

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

Field details

AES_GCM

public static final String AES_GCM = "AES/GCM/NoPadding"

AES/GCM/NoPadding – recommended authenticated mode for AES.

AES_CBC_PKCS5

public static final String AES_CBC_PKCS5 = "AES/CBC/PKCS5Padding"

AES/CBC/PKCS5Padding – block-chained AES with PKCS#5 padding.

AES_CBC

public static final String AES_CBC = "AES/CBC/NoPadding"

AES/CBC/NoPadding – raw CBC, caller must pre-pad to a 16-byte boundary.

AES_ECB_PKCS5

public static final String AES_ECB_PKCS5 = "AES/ECB/PKCS5Padding"

AES/ECB/PKCS5Padding – legacy interop only. ECB leaks structure; avoid for new designs.

RSA_OAEP_SHA256

public static final String RSA_OAEP_SHA256 = "RSA/ECB/OAEPWithSHA-256AndMGF1Padding"

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.

RSA_PKCS1

public static final String RSA_PKCS1 = "RSA/ECB/PKCS1Padding"

RSA/ECB/PKCS1Padding – legacy RSA padding, kept for interop.

Method details

aesEncrypt

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

Encrypts with AES.

Parameters

transformation String: one of AES_GCM, AES_CBC_PKCS5, AES_CBC, AES_ECB_PKCS5
key SecretKey: AES key (16, 24 or 32 bytes for AES-128/192/256)
iv byte[]: initialisation vector for CBC (16 bytes) / nonce for GCM (12 bytes recommended). Pass null for ECB.
aad byte[]: associated authenticated data – GCM only, may be null
plaintext byte[]: data to encrypt

aesDecrypt

public static byte[] aesDecrypt(String transformation, SecretKey key, byte[] iv, byte[] aad, byte[] ciphertext)

Decrypts AES ciphertext produced by aesEncrypt. 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.