code: 	PlainText decrypt(SecretKey key, CipherText ciphertext) throws EncryptionException;
  	
  	/**
  	 * Create a digital signature for the provided data and return it in a
  	 * string.
  	 * <p>
  	 * <b>Limitations:</b> A new public/private key pair used for ESAPI 2.0 digital
  	 * signatures with this method and {@link #verifySignature(String, String)}
  	 * are dynamically created when the default reference implementation class,
  	 * {@link org.owasp.esapi.reference.crypto.JavaEncryptor} is first created.
  	 * Because this key pair is not persisted nor is the public key shared,
  	 * this method and the corresponding {@link #verifySignature(String, String)}
  	 * can not be used with expected results across JVM instances. This limitation
  	 * will be addressed in ESAPI 2.1.
  	 * </p>
  	 * 
  	 * @param data
  	 *      the data to sign
  	 * 
  	 * @return 
  	 * 		the digital signature stored as a String
  	 * 
  	 * @throws EncryptionException
  	 * 		if the specified signature algorithm cannot be found
  	 */
  