Package org.bouncycastle.crypto.engines

## Class ChaChaEngine

- java.lang.Object
- - org.bouncycastle.crypto.engines.Salsa20Engine
  - - org.bouncycastle.crypto.engines.ChaChaEngine

- All Implemented Interfaces:
    `SkippingCipher`, `SkippingStreamCipher`, `StreamCipher`

      public class ChaChaEngine
      extends Salsa20Engine

  Implementation of Daniel J. Bernstein's ChaCha stream cipher.

- - ### Field Summary

    - ### Fields inherited from class org.bouncycastle.crypto.engines.Salsa20Engine

      `DEFAULT_ROUNDS, engineState, rounds, sigma, tau, x`

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `ChaChaEngine()` | Creates a 20 rounds ChaCha engine.
    `ChaChaEngine​(int rounds)` | Creates a ChaCha engine with a specific number of rounds.

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `protected void` | `advanceCounter()` |
    `protected void` | `advanceCounter​(long diff)` |
    `static void` | `chachaCore​(int rounds, int[] input, int[] x)` | ChaCha function
    `protected void` | `generateKeyStream​(byte[] output)` |
    `java.lang.String` | `getAlgorithmName()` | Return the name of the algorithm the cipher implements.
    `protected long` | `getCounter()` |
    `protected void` | `resetCounter()` |
    `protected void` | `retreatCounter()` |
    `protected void` | `retreatCounter​(long diff)` |
    `protected void` | `setKey​(byte[] keyBytes, byte[] ivBytes)` |

    - ### Methods inherited from class org.bouncycastle.crypto.engines.Salsa20Engine

      `getNonceSize, getPosition, init, packTauOrSigma, processBytes, reset, returnByte, salsaCore, seekTo, skip`

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

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

- - ### Constructor Detail

    - #### ChaChaEngine

          public ChaChaEngine()

      Creates a 20 rounds ChaCha engine.

    - #### ChaChaEngine

          public ChaChaEngine​(int rounds)

      Creates a ChaCha engine with a specific number of rounds.
      Parameters:
        `rounds` - the number of rounds (must be an even number).

  - ### Method Detail

    - #### getAlgorithmName

          public java.lang.String getAlgorithmName()

      Description copied from interface: `StreamCipher`
      Return the name of the algorithm the cipher implements.
      Specified by:
        `getAlgorithmName` in interface `StreamCipher`
      Overrides:
        `getAlgorithmName` in class `Salsa20Engine`
      Returns:
        the name of the algorithm the cipher implements.

    - #### advanceCounter

          protected void advanceCounter​(long diff)

      Overrides:
        `advanceCounter` in class `Salsa20Engine`

    - #### advanceCounter

          protected void advanceCounter()

      Overrides:
        `advanceCounter` in class `Salsa20Engine`

    - #### retreatCounter

          protected void retreatCounter​(long diff)

      Overrides:
        `retreatCounter` in class `Salsa20Engine`

    - #### retreatCounter

          protected void retreatCounter()

      Overrides:
        `retreatCounter` in class `Salsa20Engine`

    - #### getCounter

          protected long getCounter()

      Overrides:
        `getCounter` in class `Salsa20Engine`

    - #### resetCounter

          protected void resetCounter()

      Overrides:
        `resetCounter` in class `Salsa20Engine`

    - #### setKey

          protected void setKey​(byte[] keyBytes,
                                byte[] ivBytes)

      Overrides:
        `setKey` in class `Salsa20Engine`

    - #### generateKeyStream

          protected void generateKeyStream​(byte[] output)

      Overrides:
        `generateKeyStream` in class `Salsa20Engine`

    - #### chachaCore

          public static void chachaCore​(int rounds,
                                        int[] input,
                                        int[] x)

      ChaCha function
      Parameters:
        `input` - input data