Class CipherOutputStream

java.lang.Object
java.io.OutputStream
java.io.FilterOutputStream
javax.crypto.CipherOutputStream
All Implemented Interfaces:
Closeable,Flushable,AutoCloseable
public classCipherOutputStreamextendsFilterOutputStream
ACipherOutputStream is composed of anOutputStream and aCipher object so that write() methods first process the data before writing them out to the underlyingOutputStream. TheCipher object must be fully initialized before being used by aCipherOutputStream.

For example, if theCipher object is initialized for encryption, theCipherOutputStream will attempt to encrypt data before writing out the encrypted data.

This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classesjava.io.OutputStream andjava.io.FilterOutputStream. This class has exactly those methods specified in its ancestor classes, and overrides them all. Moreover, this class catches all exceptions that are not thrown by its ancestor classes. In particular, this class catchesBadPaddingException and other exceptions thrown by failed integrity checks during decryption. These exceptions are not re-thrown, so the client will not be informed that integrity checks failed. Because of this behavior, this class may not be suitable for use with decryption in an authenticated mode of operation (e.g. GCM) if the application requires explicit notification when authentication fails. Such an application can use theCipher API directly as an alternative to using this class.

It is crucial for a programmer using this class not to use methods that are not defined or overridden in this class (such as a new method or constructor that is later added to one of the super classes), because the design and implementation of those methods are unlikely to have considered security impact with regard toCipherOutputStream.

Since:
1.4
See Also:

  • Field Summary

    Fields declared in class java.io.FilterOutputStream

    out

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    Constructs aCipherOutputStream from anOutputStream without specifying aCipher object.
     
    Constructs aCipherOutputStream from anOutputStream and aCipher object.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    Closes this output stream and releases any system resources associated with this stream.
    void
    Flushes this output stream by forcing any buffered output bytes that have already been processed by the encapsulatedCipher object to be written out.
    void
    write(byte[] b)
    Writesb.length bytes from the specified byte array to this output stream.
    void
    write(byte[] b, int off, int len)
    Writeslen bytes from the specified byte array starting at offsetoff to this output stream.
    void
    write(int b)
    Writes the specified byte to this output stream.

    Methods declared in class java.io.OutputStream

    nullOutputStream

  • Constructor Details

    • CipherOutputStream

      public CipherOutputStream(OutputStream os,Cipher c)
      Constructs aCipherOutputStream from anOutputStream and aCipher object.
      Note: if the specified output stream or cipher isnull,a NullPointerException may be thrown later when they are used.
      Parameters:
      os - theOutputStream object
      c - an initializedCipher object

    • CipherOutputStream

      protected CipherOutputStream(OutputStream os)
      Constructs aCipherOutputStream from anOutputStream without specifying aCipher object. This has the effect of constructing aCipherOutputStream using aNullCipher.
      Note: if the specified output stream isnull, aNullPointerException may be thrown later when it is used.
      Parameters:
      os - theOutputStream object

  • Method Details

    • write

      public void write(int b) throwsIOException
      Writes the specified byte to this output stream.
      Overrides:
      write in class FilterOutputStream
      Parameters:
      b - thebyte.
      Throws:
      IOException - if an I/O error occurs.

    • write

      public void write(byte[] b) throwsIOException
      Writesb.length bytes from the specified byte array to this output stream.

      Thewrite method ofCipherOutputStream calls thewrite method of three arguments with the three argumentsb,0, andb.length.

      Overrides:
      write in class FilterOutputStream
      Parameters:
      b - the data.
      Throws:
      NullPointerException - ifb isnull.
      IOException - if an I/O error occurs.
      See Also:

    • write

      public void write(byte[] b, int off, int len) throwsIOException
      Writeslen bytes from the specified byte array starting at offsetoff to this output stream.
      Overrides:
      write in class FilterOutputStream
      Parameters:
      b - the data.
      off - the start offset in the data.
      len - the number of bytes to write.
      Throws:
      IOException - if an I/O error occurs.
      See Also:

    • flush

      public void flush() throwsIOException
      Flushes this output stream by forcing any buffered output bytes that have already been processed by the encapsulatedCipher object to be written out.

      Any bytes buffered by the encapsulatedCipher object and waiting to be processed by it will not be written out. For example, if the encapsulatedCipher object is a block cipher, and the total number of bytes written using one of thewrite methods is less than the cipher's block size, no bytes will be written out.

      Specified by:
      flush in interface Flushable
      Overrides:
      flush in class FilterOutputStream
      Throws:
      IOException - if an I/O error occurs.
      See Also:

    • close

      public void close() throwsIOException
      Closes this output stream and releases any system resources associated with this stream.

      This method invokes thedoFinal method of the encapsulatedCipher object, which causes any bytes buffered by the encapsulatedCipher object to be processed. The result is written out by calling theflush method of this output stream.

      This method resets the encapsulatedCipher object to its initial state and calls theclose method of the underlying output stream.

      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class FilterOutputStream
      Throws:
      IOException - if an I/O error occurs.
      See Also: