1 /*
   2  * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package javax.crypto.spec;
  27 
  28 import java.security.spec.AlgorithmParameterSpec;
  29 import java.util.Objects;
  30 
  31 /**
  32  * This class specifies the parameters used with the
  33  * <a href="https://tools.ietf.org/html/rfc7539"><i>ChaCha20</i></a>
  34  * algorithm.
  35  *
  36  * <p> The parameters consist of a 96-bit nonce and an initial
  37  * counter value expressed as a 32-bit integer.
  38  *
  39  * <p> This class can be used to initialize a {@code Cipher} object that
  40  * implements the <i>ChaCha20</i> algorithm.
  41  */
  42 public class ChaCha20ParameterSpec implements AlgorithmParameterSpec {
  43 
  44     // The nonce length is defined by the spec as 96 bits in length.
  45     private static final int NONCE_LENGTH = 12;
  46 
  47     private final byte[] nonce;
  48     private final int counter;
  49 
  50     /**
  51      * Constructs a parameter set for ChaCha20 from the given nonce
  52      * and counter.
  53      *
  54      * @param nonce a 96-bit nonce value
  55      * @param counter the initial counter value
  56      *
  57      * @throws NullPointerException if {@code nonce} is {@code null}
  58      * @throws IllegalArgumentException if {@code nonce} is not 96-bits
  59      *      in length.
  60      */
  61     public ChaCha20ParameterSpec(byte[] nonce, int counter) {
  62         this.counter = counter;
  63 
  64         Objects.requireNonNull(nonce, "Nonce must be non-null");
  65         if (nonce.length == 12) {
  66             this.nonce = nonce.clone();
  67         } else {
  68             throw new IllegalArgumentException(
  69                     "Nonce must be 96-bits in length");
  70         }
  71     }
  72 
  73     /**
  74      * Returns the nonce value.
  75      *
  76      * @return the nonce value.  This method returns a new array each time
  77      * this method is called.
  78      */
  79     public byte[] getNonce() {
  80         return nonce.clone();
  81     }
  82 
  83     /**
  84      * Returns the configured counter value.
  85      *
  86      * @return the counter value.
  87      */
  88     public int getCounter() {
  89         return counter;
  90     }
  91 }