org.whispersystems.libsignal.groups.GroupCipher Maven / Gradle / Ivy

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/**
 * Copyright (C) 2014-2016 Open Whisper Systems
 *
 * Licensed according to the LICENSE file in this repository.
 */
package org.whispersystems.libsignal.groups;

import org.signal.client.internal.Native;
import org.whispersystems.libsignal.DuplicateMessageException;
import org.whispersystems.libsignal.InvalidKeyIdException;
import org.whispersystems.libsignal.InvalidMessageException;
import org.whispersystems.libsignal.LegacyMessageException;
import org.whispersystems.libsignal.NoSessionException;
import org.whispersystems.libsignal.groups.state.SenderKeyStore;

import java.security.InvalidAlgorithmParameterException;
import java.security.NoSuchAlgorithmException;

/**
 * The main entry point for Signal Protocol group encrypt/decrypt operations.
 *
 * Once a session has been established with {@link org.whispersystems.libsignal.groups.GroupSessionBuilder}
 * and a {@link org.whispersystems.libsignal.protocol.SenderKeyDistributionMessage} has been
 * distributed to each member of the group, this class can be used for all subsequent encrypt/decrypt
 * operations within that session (ie: until group membership changes).
 *
 * @author Moxie Marlinspike
 */
public class GroupCipher {

  static final Object LOCK = new Object();

  private final SenderKeyStore senderKeyStore;
  private final SenderKeyName senderKeyId;

  public GroupCipher(SenderKeyStore senderKeyStore, SenderKeyName senderKeyId) {
    this.senderKeyStore = senderKeyStore;
    this.senderKeyId    = senderKeyId;
  }

  /**
   * Encrypt a message.
   *
   * @param paddedPlaintext The plaintext message bytes, optionally padded.
   * @return Ciphertext.
   * @throws NoSessionException
   */
  public byte[] encrypt(byte[] paddedPlaintext) throws NoSessionException {
    synchronized (LOCK) {
    try {
      return Native.GroupCipher_EncryptMessage(this.senderKeyId.nativeHandle(), paddedPlaintext, this.senderKeyStore);
    } catch (IllegalStateException e) {
      throw new NoSessionException(e);
    }
    }
  }

  /**
   * Decrypt a SenderKey group message.
   *
   * @param senderKeyMessageBytes The received ciphertext.
   * @return Plaintext
   * @throws LegacyMessageException
   * @throws InvalidMessageException
   * @throws DuplicateMessageException
   */
  public byte[] decrypt(byte[] senderKeyMessageBytes)
      throws LegacyMessageException, DuplicateMessageException, InvalidMessageException, NoSessionException
  {
    synchronized (LOCK) {
      try {
        return Native.GroupCipher_DecryptMessage(this.senderKeyId.nativeHandle(), senderKeyMessageBytes, this.senderKeyStore);
    } catch (IllegalStateException e) {
      throw new NoSessionException(e);
      }
    }
  }
}