http://github.com/google/tink: Tink is a small cryptographic library that provides a safe, simple, agile and fast way to accomplish some common cryptographic tasks. 
// Copyright 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
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////////////////////////////////////////////////////////////////////////////////

package com.google.crypto.tink.subtle;

import java.nio.ByteBuffer;
import java.security.GeneralSecurityException;


StreamSegmentEncrypter is a helper class that encrypts individual segments of a stream.

Instances of this interfaces are passed to ...EncryptingChannel. Each instance of a segment
encrypter is used to encrypt one stream. Typically, constructing a new StreamSegmentEncrypter
results in the generation of a new symmetric key. This new symmetric key is used to encrypt the
segments of the stream. The key itself wrapped with or derived from the key from StreamingAead
instance. The wrapped key or the salt used to derive the symmetric key is part of the header.

A StreamSegmentEncrypter has a state: it keeps the number of segments encrypted so far. This
state is used to encrypt each segment with different parameters, so that segments in the
ciphertext cannot be switched.

Since:1.1.0
/**
 * StreamSegmentEncrypter is a helper class that encrypts individual segments of a stream.
 *
 * <p>Instances of this interfaces are passed to ...EncryptingChannel. Each instance of a segment
 * encrypter is used to encrypt one stream. Typically, constructing a new StreamSegmentEncrypter
 * results in the generation of a new symmetric key. This new symmetric key is used to encrypt the
 * segments of the stream. The key itself wrapped with or derived from the key from StreamingAead
 * instance. The wrapped key or the salt used to derive the symmetric key is part of the header.
 *
 * <p>A StreamSegmentEncrypter has a state: it keeps the number of segments encrypted so far. This
 * state is used to encrypt each segment with different parameters, so that segments in the
 * ciphertext cannot be switched.
 *
 * @since 1.1.0
 */
public interface StreamSegmentEncrypter {

  
Returns the header of the ciphertext stream.

/**
   * Returns the header of the ciphertext stream.
   */
  ByteBuffer getHeader();

  
Encrypts the next plaintext segment.
This uses encryptedSegments as the segment number for the encryption.

/**
   * Encrypts the next plaintext segment.
   * This uses encryptedSegments as the segment number for the encryption.
   */
  void encryptSegment(
      ByteBuffer plaintext,
      boolean isLastSegment,
      ByteBuffer ciphertext)
      throws GeneralSecurityException;

  
Encrypt a segment consisting of two parts.
This method simplifies the case where one part of the plaintext is buffered and the other part
is passed in by the caller.

/**
   * Encrypt a segment consisting of two parts.
   * This method simplifies the case where one part of the plaintext is buffered and the other part
   * is passed in by the caller.
   */
  void encryptSegment(
        ByteBuffer part1,
        ByteBuffer part2,
        boolean isLastSegment,
        ByteBuffer ciphertext)
        throws GeneralSecurityException;
}