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

org.bouncycastle.crypto.digests

## Class ShortenedDigest

- java.lang.Object
- - org.bouncycastle.crypto.digests.ShortenedDigest

- All Implemented Interfaces:
    Digest, ExtendedDigest

      public class ShortenedDigest
      extends java.lang.Object
      implements ExtendedDigest

  Wrapper class that reduces the output length of a particular digest to only the first n bytes of the digest function.

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `ShortenedDigest(ExtendedDigest baseDigest, int length)` Base constructor.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `doFinal(byte[] out, int outOff)` close the digest, producing the final digest value.
    `java.lang.String` | `getAlgorithmName()` return the algorithm name
    `int` | `getByteLength()` Return the size in bytes of the internal buffer the digest applies it's compression function to.
    `int` | `getDigestSize()` return the size, in bytes, of the digest produced by this message digest.
    `void` | `reset()` reset the digest back to it's initial state.
    `void` | `update(byte in)` update the message digest with a single byte.
    `void` | `update(byte[] in, int inOff, int len)` update the message digest with a block of bytes.

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

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

- - ### Constructor Detail

    - #### ShortenedDigest

          public ShortenedDigest(ExtendedDigest baseDigest,
                                 int length)

      Base constructor.
      Parameters:
        `baseDigest` - underlying digest to use.
        `length` - length in bytes of the output of doFinal.
      Throws:
        `java.lang.IllegalArgumentException` - if baseDigest is null, or length is greater than baseDigest.getDigestSize().

  - ### Method Detail

    - #### getAlgorithmName

          public java.lang.String getAlgorithmName()

      Description copied from interface: `Digest`
      return the algorithm name
      Specified by:
        `getAlgorithmName` in interface `Digest`
      Returns:
        the algorithm name

    - #### getDigestSize

          public int getDigestSize()

      Description copied from interface: `Digest`
      return the size, in bytes, of the digest produced by this message digest.
      Specified by:
        `getDigestSize` in interface `Digest`
      Returns:
        the size, in bytes, of the digest produced by this message digest.

    - #### update

          public void update(byte in)

      Description copied from interface: `Digest`
      update the message digest with a single byte.
      Specified by:
        `update` in interface `Digest`
      Parameters:
        `in` - the input byte to be entered.

    - #### update

          public void update(byte[] in,
                             int inOff,
                             int len)

      Description copied from interface: `Digest`
      update the message digest with a block of bytes.
      Specified by:
        `update` in interface `Digest`
      Parameters:
        `in` - the byte array containing the data.
        `inOff` - the offset into the byte array where the data starts.
        `len` - the length of the data.

    - #### doFinal

          public int doFinal(byte[] out,
                             int outOff)

      Description copied from interface: `Digest`
      close the digest, producing the final digest value. The doFinal call leaves the digest reset.
      Specified by:
        `doFinal` in interface `Digest`
      Parameters:
        `out` - the array the digest is to be copied into.
        `outOff` - the offset into the out array the digest is to start at.

    - #### reset

          public void reset()

      Description copied from interface: `Digest`
      reset the digest back to it's initial state.
      Specified by:
        `reset` in interface `Digest`

    - #### getByteLength

          public int getByteLength()

      Description copied from interface: `ExtendedDigest`
      Return the size in bytes of the internal buffer the digest applies it's compression function to.
      Specified by:
        `getByteLength` in interface `ExtendedDigest`
      Returns:
        byte length of the digests internal buffer.