| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.pirk.encryption; |
| |
| import java.math.BigInteger; |
| |
| import org.apache.pirk.utils.SystemConfiguration; |
| |
| import com.squareup.jnagmp.Gmp; |
| |
| /** |
| * This class is designed to offer a one-stop-shop for invoking the desired version of modPow |
| */ |
| public final class ModPowAbstraction |
| { |
| private static boolean useGMPForModPow = SystemConfiguration.isSetTrue("paillier.useGMPForModPow"); |
| |
| private static boolean useGMPConstantTimeMethods = SystemConfiguration.isSetTrue("paillier.GMPConstantTimeMode"); |
| |
| /** |
| * Performs modPow: ({@code base}^{@code exponent}) mod {@code modulus} |
| * |
| * This method uses the values of {@code paillier.useGMPForModPow} and {@code paillier.GMPConstantTimeMode} as they were when the class was loaded to decide |
| * which implementation of modPow to invoke. |
| * |
| * These values can be reloaded by invoking static method {@code ModPowAbstraction.reloadConfiguration()} |
| * |
| * @return The result of modPow |
| */ |
| public static BigInteger modPow(BigInteger base, BigInteger exponent, BigInteger modulus) |
| { |
| BigInteger result; |
| |
| if (useGMPForModPow) |
| { |
| if (useGMPConstantTimeMethods) |
| { |
| // Use GMP and use the "timing attack resistant" method |
| // The timing attack resistance slows down performance and is not necessarily proven to block timing attacks. |
| // Before getting concerned, please carefully consider your threat model |
| // and if you really believe that you may need it |
| result = Gmp.modPowSecure(base, exponent, modulus); |
| } |
| else |
| { |
| // The word "insecure" here does not imply any actual, direct insecurity. |
| // It denotes that this function runs as fast as possible without trying to |
| // counteract timing attacks. This is probably what you want unless you have a |
| // compelling reason why you believe that this environment is safe enough to house |
| // your keys but doesn't protect you from another entity on the machine watching |
| // how long the program runs. |
| result = Gmp.modPowInsecure(base, exponent, modulus); |
| } |
| } |
| else |
| { |
| // If GMP isn't used, BigInteger's built-in modPow is used. |
| // This is significantly slower but has the virtue of working everywhere. |
| result = base.modPow(exponent, modulus); |
| } |
| |
| return result; |
| } |
| |
| public static BigInteger modPow(long base, BigInteger exponent, BigInteger modulus) |
| { |
| return modPow(BigInteger.valueOf(base), exponent, modulus); |
| } |
| |
| public static void reloadConfiguration() |
| { |
| useGMPForModPow = SystemConfiguration.isSetTrue("paillier.useGMPForModPow"); |
| useGMPConstantTimeMethods = SystemConfiguration.isSetTrue("paillier.GMPConstantTimeMode"); |
| } |
| } |