de.schlichtherle.crypto.io
Class CipherOutputStream

java.lang.Object
  java.io.OutputStream
      java.io.FilterOutputStream
          de.schlichtherle.crypto.io.CipherOutputStream

All Implemented Interfaces:

Closeable, Flushable

Direct Known Subclasses:

RaesOutputStream

public class CipherOutputStream
extends FilterOutputStream

Similar to javax.crypto.CipherOutputStream, with some exceptions:

• This implementation uses Bouncy Castle's lightweight API. In particular, a BufferedBlockCipher is used for ciphering.
• The cipher used for encryption or decryption is accessible to subclasses.
• The flush() method just flushes the underlying output stream and has no effect on the cipher.
• A finish() method has been added to allow finishing the output (probably producing padding bytes) without closing the output. This could be used in a subclass to produce a trailer with additional information about the ciphered data (e.g. a MAC).

Author:

Christian Schlichtherle

Field Summary

protected BufferedBlockCipher

cipher The buffered block cipher used for preprocessing the output.

Fields inherited from class java.io.FilterOutputStream

out

Constructor Summary

CipherOutputStream(OutputStream out, BufferedBlockCipher cipher)
Creates a new instance of CipherOutputStream.

Method Summary

void	close() Closes this output stream and releases any resources associated with it.
void	finish() Finishes this stream and resets it to it's initial state.
void	write(byte[] buf, int off, int len) Ciphers and writes the contents of the given byte array to the underlying output stream.
void	write(int b) Ciphers and writes the given byte to the underlying output stream.

Methods inherited from class java.io.FilterOutputStream

flush, write

Methods inherited from class java.lang.Object

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

Field Detail

cipher

protected BufferedBlockCipher cipher

The buffered block cipher used for preprocessing the output.

Constructor Detail

CipherOutputStream

public CipherOutputStream(OutputStream out,
                          BufferedBlockCipher cipher)

Creates a new instance of CipherOutputStream. Please note that unlike javax.crypto.CipherOutputStream, the cipher does not need to be initialized before calling this constructor. However, the cipher must be initialized before anything is actually written to this stream or before this stream is closed.

Parameters:

out - The output stream to write the encrypted or decrypted data to. Maybe null if initialized by the subclass constructor.

cipher - The cipher to use for encryption or decryption. Maybe null for subsequent initialization by a subclass.

Method Detail

write

public void write(int b)
           throws IOException

Ciphers and writes the given byte to the underlying output stream.

Overrides:

write in class FilterOutputStream

Parameters:

b - The byte to cipher and write.

Throws:

IOException - If out or cipher aren't properly initialized, the stream has been closed or an I/O error occured.

write

public void write(byte[] buf,
                  int off,
                  int len)
           throws IOException

Ciphers and writes the contents of the given byte array to the underlying output stream.

Overrides:

write in class FilterOutputStream

Parameters:

buf - The buffer holding the data to cipher and write.

off - The start offset in the data buffer.

len - The number of bytes to cipher and write.

Throws:

IOException - If out or cipher aren't properly initialized, the stream has been closed or an I/O error occured.

finish

public void finish()
            throws IOException

Finishes this stream and resets it to it's initial state. Calling this method causes all remaining buffered bytes to be written, padding to be added if necessary and the underlying output stream to get flushed.

Please note that subsequent calls to any write operations after this method may cause an error in the output data if padding is used!

Throws:

IOException - If out or cipher aren't properly initialized, the stream has been closed, an I/O error occured the cipher text is invalid, i.e. required padding information is missing.

close

public void close()
           throws IOException

Closes this output stream and releases any resources associated with it. This method calls finish() and then closes and nullifies the underlying output stream FilterOutputStream.out and the cipher cipher.

Specified by:

close in interface Closeable

Overrides:

close in class FilterOutputStream

Throws:

IOException - If an I/O error occurs.