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

org.bouncycastle.crypto.hash2curve

## Interface MessageExpansion

- All Known Implementing Classes:
    XmdMessageExpansion

      public interface MessageExpansion

  The MessageExpansion interface defines a contract for expanding a message.

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `byte[]` | `expandMessage(byte[] msg, byte[] dst, int lenInBytes)` Expands the given message to match the specified length in bytes.

- - ### Method Detail

    - #### expandMessage

          byte[] expandMessage(byte[] msg,
                               byte[] dst,
                               int lenInBytes)

      Expands the given message to match the specified length in bytes.
      Parameters:
        `msg` - the original message to be expanded
        `dst` - domain separation tag
        `lenInBytes` - the desired length of the expanded message in bytes
      Returns:
        the expanded message as a byte array