ByteExtensions.java

/**
 * Copyright (c) Microsoft Corporation. All rights reserved.
 * Licensed under the MIT License. See License.txt in the project root for
 * license information.
 */

package com.microsoft.azure.keyvault.cryptography;

import java.util.Arrays;

public final class ByteExtensions {

    public static byte[] or( byte[] self, byte[] other )
    {
        return or( self, other, 0 );
    }

    public static byte[] or( byte[] self, byte[] other, int offset )
    {
        if ( self == null )
            throw new IllegalArgumentException( "self" );

        if ( other == null )
            throw new IllegalArgumentException( "other" );

        if ( self.length > other.length - offset )
            throw new IllegalArgumentException( "self and other lengths do not match" );

        byte[] result = new byte[self.length];

        for ( int i = 0; i < self.length; i++ )
        {
            result[i] = (byte)( self[i] | other[offset + i] );
        }

        return result;
    }
    
    public static byte[] xor( byte[] self, byte[] other ) {
    	return xor( self, other, 0 );
    }

    static byte[] xor( byte[] self, byte[] other, int offset )
    {
        if ( self == null )
            throw new IllegalArgumentException( "self" );

        if ( other == null )
            throw new IllegalArgumentException( "other" );

        if ( self.length > other.length - offset )
            throw new IllegalArgumentException( "self and other lengths do not match" );

        byte[] result = new byte[self.length];

        for ( int i = 0; i < self.length; i++ )
        {
            result[i] = (byte)( self[i] ^ other[offset + i] );
        }

        return result;
    }

    public static void zero( byte[] self )
    {
        if ( self != null ) {
            Arrays.fill(self, (byte)0);
        }
    }
    
    /**
     * Compares two byte arrays in constant time.
     * 
     * @param self
     *      The first byte array to compare 
     * @param other
     *      The second byte array to compare
     * @return
     *      True if the two byte arrays are equal.
     */
    public static boolean sequenceEqualConstantTime( byte[] self, byte[] other )
    {
        if ( self == null )
            throw new IllegalArgumentException( "self" );

        if ( other == null )
            throw new IllegalArgumentException( "other" );

        // Constant time comparison of two byte arrays
        long difference = ( self.length & 0xffffffffl ) ^ ( other.length & 0xffffffffl );

        for ( int i = 0; i < self.length && i < other.length; i++ )
        {
            difference |= ( self[i] ^ other[i] ) & 0xffffffffl;
        }

        return difference == 0;
    }

}