BufferedBlockCipher (Bouncy Castle Library 1.85 API Specification)
Date: 2026-07-12

org.bouncycastle.crypto

## Class BufferedBlockCipher

- java.lang.Object
- - org.bouncycastle.crypto.BufferedBlockCipher

- Direct Known Subclasses:
    DefaultBufferedBlockCipher

      public class BufferedBlockCipher
      extends java.lang.Object

  A wrapper class that allows block ciphers to be used to process data in a piecemeal fashion. The BufferedBlockCipher outputs a block only when the buffer is full and more data is being added, or on a doFinal.

  Note: in the case where the underlying cipher is either a CFB cipher or an OFB one the last block may not be a multiple of the block size.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected byte[]` | `buf`
    `protected int` | `bufOff`
    `protected BlockCipher` | `cipher`
    `protected boolean` | `forEncryption`
    `protected MultiBlockCipher` | `mbCipher`
    `protected boolean` | `partialBlockOkay`
    `protected boolean` | `pgpCFB`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `BufferedBlockCipher(BlockCipher cipher)` Deprecated. use the constructor on DefaultBufferedBlockCipher.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `doFinal(byte[] out, int outOff)` Process the last block in the buffer.
    `int` | `getBlockSize()` return the blocksize for the underlying cipher.
    `int` | `getOutputSize(int length)` return the size of the output buffer required for an update plus a doFinal with an input of 'length' bytes.
    `BlockCipher` | `getUnderlyingCipher()` return the cipher this object wraps.
    `int` | `getUpdateOutputSize(int len)` return the size of the output buffer required for an update an input of len bytes.
    `void` | `init(boolean forEncryption, CipherParameters params)` initialise the cipher.
    `int` | `processByte(byte in, byte[] out, int outOff)` process a single byte, producing an output block if necessary.
    `int` | `processBytes(byte[] in, int inOff, int len, byte[] out, int outOff)` process an array of bytes, producing output if necessary.
    `void` | `reset()` Reset the buffer and cipher.

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### buf

          protected byte[] buf

    - #### bufOff

          protected int bufOff

    - #### forEncryption

          protected boolean forEncryption

    - #### cipher

          protected BlockCipher cipher

    - #### mbCipher

          protected MultiBlockCipher mbCipher

    - #### partialBlockOkay

          protected boolean partialBlockOkay

    - #### pgpCFB

          protected boolean pgpCFB

  - ### Constructor Detail

    - #### BufferedBlockCipher

          public BufferedBlockCipher(BlockCipher cipher)

      Deprecated. use the constructor on DefaultBufferedBlockCipher.
      Create a buffered block cipher without padding.
      Parameters:
        `cipher` - the underlying block cipher this buffering object wraps.

  - ### Method Detail

    - #### getUnderlyingCipher

          public BlockCipher getUnderlyingCipher()

      return the cipher this object wraps.
      Returns:
        the cipher this object wraps.

    - #### init

          public void init(boolean forEncryption,
                           CipherParameters params)
                    throws java.lang.IllegalArgumentException

      initialise the cipher.
      Parameters:
        `forEncryption` - if true the cipher is initialised for encryption, if false for decryption.
        `params` - the key and other data required by the cipher.
      Throws:
        `java.lang.IllegalArgumentException` - if the params argument is inappropriate.

    - #### getBlockSize

          public int getBlockSize()

      return the blocksize for the underlying cipher.
      Returns:
        the blocksize for the underlying cipher.

    - #### getUpdateOutputSize

          public int getUpdateOutputSize(int len)

      return the size of the output buffer required for an update an input of len bytes.
      Parameters:
        `len` - the length of the input.
      Returns:
        the space required to accommodate a call to update with len bytes of input.

    - #### getOutputSize

          public int getOutputSize(int length)

      return the size of the output buffer required for an update plus a doFinal with an input of 'length' bytes.
      Parameters:
        `length` - the length of the input.
      Returns:
        the space required to accommodate a call to update and doFinal with 'length' bytes of input.

    - #### processByte

          public int processByte(byte in,
                                 byte[] out,
                                 int outOff)
                          throws DataLengthException,
                                 java.lang.IllegalStateException

      process a single byte, producing an output block if necessary.
      Parameters:
        `in` - the input byte.
        `out` - the space for any output that might be produced.
        `outOff` - the offset from which the output will be copied.
      Returns:
        the number of output bytes copied to out.
      Throws:
        `DataLengthException` - if there isn't enough space in out.
        `java.lang.IllegalStateException` - if the cipher isn't initialised.

    - #### processBytes

          public int processBytes(byte[] in,
                                  int inOff,
                                  int len,
                                  byte[] out,
                                  int outOff)
                           throws DataLengthException,
                                  java.lang.IllegalStateException

      process an array of bytes, producing output if necessary.
      Parameters:
        `in` - the input byte array.
        `inOff` - the offset at which the input data starts.
        `len` - the number of bytes to be copied out of the input array.
        `out` - the space for any output that might be produced.
        `outOff` - the offset from which the output will be copied.
      Returns:
        the number of output bytes copied to out.
      Throws:
        `DataLengthException` - if there isn't enough space in out.
        `java.lang.IllegalStateException` - if the cipher isn't initialised.

    - #### doFinal

          public int doFinal(byte[] out,
                             int outOff)
                      throws DataLengthException,
                             java.lang.IllegalStateException,
                             InvalidCipherTextException

      Process the last block in the buffer.
      Parameters:
        `out` - the array the block currently being held is copied into.
        `outOff` - the offset at which the copying starts.
      Returns:
        the number of output bytes copied to out.
      Throws:
        `DataLengthException` - if there is insufficient space in out for the output, or the input is not block size aligned and should be.
        `java.lang.IllegalStateException` - if the underlying cipher is not initialised.
        `InvalidCipherTextException` - if padding is expected and not found.
        `DataLengthException` - if the input is not block size aligned.

    - #### reset

          public void reset()

      Reset the buffer and cipher. After resetting the object is in the same state as it was after the last init (if there was one).