CAST6Engine (Bouncy Castle Library 1.85 API Specification)
Date: 2026-07-12

org.bouncycastle.crypto.engines

## Class CAST6Engine

- java.lang.Object
- - org.bouncycastle.crypto.engines.CAST5Engine
  - - org.bouncycastle.crypto.engines.CAST6Engine

- All Implemented Interfaces:
    BlockCipher

      public final class CAST6Engine
      extends CAST5Engine

  A class that provides CAST6 key encryption operations, such as encoding data and generating keys. All the algorithms herein are from the Internet RFC RFC2612 - CAST6 (128bit block, 128-256bit key) and implement a simplified cryptography interface.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected int[]` | `_Km`
    `protected int[]` | `_Kr`
    `protected int[]` | `_Tm`
    `protected int[]` | `_Tr`
    `protected static int` | `BLOCK_SIZE`
    `protected static int` | `ROUNDS`

    - ### Fields inherited from class org.bouncycastle.crypto.engines.CAST5Engine

      `MAX_ROUNDS, RED_ROUNDS`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `CAST6Engine()`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `CAST_Decipher(int A, int B, int C, int D, int[] result)` Does the 12 quad rounds rounds to decrypt the block.
    `protected void` | `CAST_Encipher(int A, int B, int C, int D, int[] result)` Does the 12 quad rounds rounds to encrypt the block.
    `protected int` | `decryptBlock(byte[] src, int srcIndex, byte[] dst, int dstIndex)` Decrypt the given input starting at the given offset and place the result in the provided buffer starting at the given offset.
    `protected int` | `encryptBlock(byte[] src, int srcIndex, byte[] dst, int dstIndex)` Encrypt the given input starting at the given offset and place the result in the provided buffer starting at the given offset.
    `java.lang.String` | `getAlgorithmName()` Return the name of the algorithm the cipher implements.
    `int` | `getBlockSize()` Return the block size for this cipher (in bytes).
    `void` | `reset()` Reset the cipher.
    `protected void` | `setKey(byte[] key)`

    - ### Methods inherited from class org.bouncycastle.crypto.engines.CAST5Engine

      `Bits32ToBytes, Bits32ToInts, BytesTo32bits, CAST_Decipher, CAST_Encipher, F1, F2, F3, init, IntsTo32bits, processBlock`

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

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

- - ### Field Detail

    - #### ROUNDS

          protected static final int ROUNDS

      See Also:
        Constant Field Values

    - #### BLOCK_SIZE

          protected static final int BLOCK_SIZE

      See Also:
        Constant Field Values

    - #### _Kr

          protected int[] _Kr

    - #### _Km

          protected int[] _Km

    - #### _Tr

          protected int[] _Tr

    - #### _Tm

          protected int[] _Tm

  - ### Constructor Detail

    - #### CAST6Engine

          public CAST6Engine()

  - ### Method Detail

    - #### getAlgorithmName

          public java.lang.String getAlgorithmName()

      Description copied from interface: `BlockCipher`
      Return the name of the algorithm the cipher implements.
      Specified by:
        `getAlgorithmName` in interface `BlockCipher`
      Overrides:
        `getAlgorithmName` in class `CAST5Engine`
      Returns:
        the name of the algorithm the cipher implements.

    - #### reset

          public void reset()

      Description copied from interface: `BlockCipher`
      Reset the cipher. After resetting the cipher is in the same state as it was after the last init (if there was one).
      Specified by:
        `reset` in interface `BlockCipher`
      Overrides:
        `reset` in class `CAST5Engine`

    - #### getBlockSize

          public int getBlockSize()

      Description copied from interface: `BlockCipher`
      Return the block size for this cipher (in bytes).
      Specified by:
        `getBlockSize` in interface `BlockCipher`
      Overrides:
        `getBlockSize` in class `CAST5Engine`
      Returns:
        the block size for this cipher in bytes.

    - #### setKey

          protected void setKey(byte[] key)

      Overrides:
        `setKey` in class `CAST5Engine`

    - #### encryptBlock

          protected int encryptBlock(byte[] src,
                                     int srcIndex,
                                     byte[] dst,
                                     int dstIndex)

      Encrypt the given input starting at the given offset and place the result in the provided buffer starting at the given offset.
      Overrides:
        `encryptBlock` in class `CAST5Engine`
      Parameters:
        `src` - The plaintext buffer
        `srcIndex` - An offset into src
        `dst` - The ciphertext buffer
        `dstIndex` - An offset into dst

    - #### decryptBlock

          protected int decryptBlock(byte[] src,
                                     int srcIndex,
                                     byte[] dst,
                                     int dstIndex)

      Decrypt the given input starting at the given offset and place the result in the provided buffer starting at the given offset.
      Overrides:
        `decryptBlock` in class `CAST5Engine`
      Parameters:
        `src` - The plaintext buffer
        `srcIndex` - An offset into src
        `dst` - The ciphertext buffer
        `dstIndex` - An offset into dst

    - #### CAST_Encipher

          protected final void CAST_Encipher(int A,
                                             int B,
                                             int C,
                                             int D,
                                             int[] result)

      Does the 12 quad rounds rounds to encrypt the block.
      Parameters:
        `A` - the 00-31 bits of the plaintext block
        `B` - the 32-63 bits of the plaintext block
        `C` - the 64-95 bits of the plaintext block
        `D` - the 96-127 bits of the plaintext block
        `result` - the resulting ciphertext

    - #### CAST_Decipher

          protected final void CAST_Decipher(int A,
                                             int B,
                                             int C,
                                             int D,
                                             int[] result)

      Does the 12 quad rounds rounds to decrypt the block.
      Parameters:
        `A` - the 00-31 bits of the ciphertext block
        `B` - the 32-63 bits of the ciphertext block
        `C` - the 64-95 bits of the ciphertext block
        `D` - the 96-127 bits of the ciphertext block
        `result` - the resulting plaintext