Example usage for org.bouncycastle.crypto.generators Poly1305KeyGenerator clamp

Introduction

In this page you can find the example usage for org.bouncycastle.crypto.generators Poly1305KeyGenerator clamp.

Prototype

public static void clamp(byte[] key) 

Source Link

Document

Modifies an existing 32 byte key value to comply with the requirements of the Poly1305 key by clearing required bits in the r (second 16 bytes) portion of the key.
Specifically:

• r[3], r[7], r[11], r[15] have top four bits clear (i.e., are {0, 1, .

  Usage

  From source file:ch.lamacrypt.internal.crypto.CPCipher.java

  License:Open Source License

  /**
   * Initializes Poly1305 with the given instance of ChaCha20Engine
   *
   * @param cipher//from   w  w w.j a  va2s  .  c o m
   */
  private void initMAC(ChaChaEngine cipher) {
      byte[] firstBlock = new byte[64];
      cipher.processBytes(firstBlock, 0, firstBlock.length, firstBlock, 0);
  
      // NOTE: The BC implementation puts 'r' after 'k'
      System.arraycopy(firstBlock, 0, firstBlock, 32, 16);
      KeyParameter macKey = new KeyParameter(firstBlock, 16, 32);
      Poly1305KeyGenerator.clamp(macKey.getKey());
      mac.init(macKey);
  }
  

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