SecureRandom.java revision 3909
2362N/A * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved. 0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 0N/A * This code is free software; you can redistribute it and/or modify it 0N/A * under the terms of the GNU General Public License version 2 only, as 2362N/A * published by the Free Software Foundation. Oracle designates this 0N/A * particular file as subject to the "Classpath" exception as provided 2362N/A * by Oracle in the LICENSE file that accompanied this code. 0N/A * This code is distributed in the hope that it will be useful, but WITHOUT 0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 0N/A * version 2 for more details (a copy is included in the LICENSE file that 0N/A * accompanied this code). 0N/A * You should have received a copy of the GNU General Public License version 0N/A * 2 along with this work; if not, write to the Free Software Foundation, 0N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 2362N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 2362N/A * or visit www.oracle.com if you need additional information or have any 0N/A * This class provides a cryptographically strong random number 0N/A * <p>A cryptographically strong random number 0N/A * minimally complies with the statistical random number generator tests 0N/A * <i>FIPS 140-2, Security Requirements for Cryptographic Modules</i></a>, 0N/A * Additionally, SecureRandom must produce non-deterministic output. 0N/A * Therefore any seed material passed to a SecureRandom object must be 0N/A * unpredictable, and all SecureRandom output sequences must be 0N/A * cryptographically strong, as described in 0N/A * <i>RFC 1750: Randomness Recommendations for Security</i></a>. 0N/A * <p>A caller obtains a SecureRandom instance via the 0N/A * no-argument constructor or one of the <code>getInstance</code> methods: 0N/A * SecureRandom random = new SecureRandom(); 0N/A * <p> Many SecureRandom implementations are in the form of a pseudo-random 0N/A * number generator (PRNG), which means they use a deterministic algorithm 0N/A * to produce a pseudo-random sequence from a true random seed. 0N/A * Other implementations may produce true random numbers, 0N/A * and yet others may use a combination of both techniques. 0N/A * <p> Typical callers of SecureRandom invoke the following methods 0N/A * to retrieve random bytes: 0N/A * SecureRandom random = new SecureRandom(); 0N/A * byte bytes[] = new byte[20]; 0N/A * random.nextBytes(bytes); 0N/A * <p> Callers may also invoke the <code>generateSeed</code> method 0N/A * to generate a given number of seed bytes (to seed other random number 0N/A * generators, for example): 0N/A * byte seed[] = random.generateSeed(20); 0N/A * Note: Depending on the implementation, the <code>generateSeed</code> and 0N/A * <code>nextBytes</code> methods may block as entropy is being gathered, 0N/A * for example, if they need to read from /dev/random on various unix-like 0N/A * operating systems. 0N/A * @see java.security.SecureRandomSpi 0N/A * @see java.util.Random 0N/A * @author Benjamin Renaud 0N/A * @author Josh Bloch 0N/A * The provider implementation. 0N/A * The algorithm name of null if unknown. 0N/A * Constructs a secure random number generator (RNG) implementing the 0N/A * default random number algorithm. 0N/A * <p> This constructor traverses the list of registered security Providers, 0N/A * starting with the most preferred Provider. 0N/A * A new SecureRandom object encapsulating the 0N/A * SecureRandomSpi implementation from the first 0N/A * Provider that supports a SecureRandom (RNG) algorithm is returned. 0N/A * If none of the Providers support a RNG algorithm, 0N/A * then an implementation-specific default is returned. 0N/A * <p> Note that the list of registered providers may be retrieved via 0N/A * the {@link Security#getProviders() Security.getProviders()} method. 0N/A * <p> See the SecureRandom section in the <a href= 0N/A * Java Cryptography Architecture Standard Algorithm Name Documentation</a> 0N/A * for information about standard RNG algorithm names. 0N/A * <p> The returned SecureRandom object has not been seeded. To seed the 0N/A * returned object, call the <code>setSeed</code> method. 0N/A * If <code>setSeed</code> is not called, the first call to 0N/A * <code>nextBytes</code> will force the SecureRandom object to seed itself. 0N/A * This self-seeding will not occur if <code>setSeed</code> was 0N/A * previously called. 0N/A * This call to our superclass constructor will result in a call 0N/A * to our own <code>setSeed</code> method, which will return 0N/A * immediately when it is passed zero. 0N/A * Constructs a secure random number generator (RNG) implementing the 0N/A * default random number algorithm. 0N/A * The SecureRandom instance is seeded with the specified seed bytes. 0N/A * <p> This constructor traverses the list of registered security Providers, 0N/A * starting with the most preferred Provider. 0N/A * A new SecureRandom object encapsulating the 0N/A * SecureRandomSpi implementation from the first 0N/A * Provider that supports a SecureRandom (RNG) algorithm is returned. 0N/A * If none of the Providers support a RNG algorithm, 0N/A * then an implementation-specific default is returned. 0N/A * <p> Note that the list of registered providers may be retrieved via 0N/A * the {@link Security#getProviders() Security.getProviders()} method. 0N/A * <p> See the SecureRandom section in the <a href= 0N/A * Java Cryptography Architecture Standard Algorithm Name Documentation</a> 0N/A * for information about standard RNG algorithm names. 0N/A * @param seed the seed. 0N/A // bummer, get the SUN implementation // never happens, because we made sure the algorithm exists // JDK 1.1 based implementations subclass SecureRandom instead of // SecureRandomSpi. They will also go through this code path because // they must call a SecureRandom constructor as it is their superclass. // If we are dealing with such an implementation, do not set the // algorithm value as it would be inaccurate. * Creates a SecureRandom object. * @param secureRandomSpi the SecureRandom implementation. * @param provider the provider. * Returns a SecureRandom object that implements the specified * Random Number Generator (RNG) algorithm. * <p> This method traverses the list of registered security Providers, * starting with the most preferred Provider. * A new SecureRandom object encapsulating the * SecureRandomSpi implementation from the first * Provider that supports the specified algorithm is returned. * <p> Note that the list of registered providers may be retrieved via * the {@link Security#getProviders() Security.getProviders()} method. * <p> The returned SecureRandom object has not been seeded. To seed the * returned object, call the <code>setSeed</code> method. * If <code>setSeed</code> is not called, the first call to * <code>nextBytes</code> will force the SecureRandom object to seed itself. * This self-seeding will not occur if <code>setSeed</code> was * @param algorithm the name of the RNG algorithm. * See the SecureRandom section in the <a href= * Java Cryptography Architecture Standard Algorithm Name Documentation</a> * for information about standard RNG algorithm names. * @return the new SecureRandom object. * @exception NoSuchAlgorithmException if no Provider supports a * SecureRandomSpi implementation for the * Returns a SecureRandom object that implements the specified * Random Number Generator (RNG) algorithm. * <p> A new SecureRandom object encapsulating the * SecureRandomSpi implementation from the specified provider * is returned. The specified provider must be registered * in the security provider list. * <p> Note that the list of registered providers may be retrieved via * the {@link Security#getProviders() Security.getProviders()} method. * <p> The returned SecureRandom object has not been seeded. To seed the * returned object, call the <code>setSeed</code> method. * If <code>setSeed</code> is not called, the first call to * <code>nextBytes</code> will force the SecureRandom object to seed itself. * This self-seeding will not occur if <code>setSeed</code> was * @param algorithm the name of the RNG algorithm. * See the SecureRandom section in the <a href= * Java Cryptography Architecture Standard Algorithm Name Documentation</a> * for information about standard RNG algorithm names. * @param provider the name of the provider. * @return the new SecureRandom object. * @exception NoSuchAlgorithmException if a SecureRandomSpi * implementation for the specified algorithm is not * available from the specified provider. * @exception NoSuchProviderException if the specified provider is not * registered in the security provider list. * @exception IllegalArgumentException if the provider name is null * Returns a SecureRandom object that implements the specified * Random Number Generator (RNG) algorithm. * <p> A new SecureRandom object encapsulating the * SecureRandomSpi implementation from the specified Provider * object is returned. Note that the specified Provider object * does not have to be registered in the provider list. * <p> The returned SecureRandom object has not been seeded. To seed the * returned object, call the <code>setSeed</code> method. * If <code>setSeed</code> is not called, the first call to * <code>nextBytes</code> will force the SecureRandom object to seed itself. * This self-seeding will not occur if <code>setSeed</code> was * @param algorithm the name of the RNG algorithm. * See the SecureRandom section in the <a href= * Java Cryptography Architecture Standard Algorithm Name Documentation</a> * for information about standard RNG algorithm names. * @param provider the provider. * @return the new SecureRandom object. * @exception NoSuchAlgorithmException if a SecureRandomSpi * implementation for the specified algorithm is not available * from the specified Provider object. * @exception IllegalArgumentException if the specified provider is null. * Returns the SecureRandomSpi of this SecureRandom object. * Returns the provider of this SecureRandom object. * @return the provider of this SecureRandom object. * Returns the name of the algorithm implemented by this SecureRandom * @return the name of the algorithm or <code>unknown</code> * if the algorithm name cannot be determined. * Reseeds this random object. The given seed supplements, rather than * replaces, the existing seed. Thus, repeated calls are guaranteed * never to reduce randomness. * Reseeds this random object, using the eight bytes contained * in the given <code>long seed</code>. The given seed supplements, * rather than replaces, the existing seed. Thus, repeated calls * are guaranteed never to reduce randomness. * <p>This method is defined for compatibility with * <code>java.util.Random</code>. * Ignore call from super constructor (as well as any other calls * unfortunate enough to be passing 0). It's critical that we * ignore call from superclass constructor, as digest has not * yet been initialized at that point. * Generates a user-specified number of random bytes. * <p> If a call to <code>setSeed</code> had not occurred previously, * the first call to this method forces this SecureRandom object * to seed itself. This self-seeding will not occur if * <code>setSeed</code> was previously called. * @param bytes the array to be filled in with random bytes. * Generates an integer containing the user-specified number of * pseudo-random bits (right justified, with leading zeros). This * method overrides a <code>java.util.Random</code> method, and serves * to provide a source of random bits to all of the methods inherited * from that class (for example, <code>nextInt</code>, * <code>nextLong</code>, and <code>nextFloat</code>). * @param numBits number of pseudo-random bits to be generated, where * 0 <= <code>numBits</code> <= 32. * @return an <code>int</code> containing the user-specified number * of pseudo-random bits (right justified, with leading zeros). * Returns the given number of seed bytes, computed using the seed * generation algorithm that this class uses to seed itself. This * call may be used to seed other random number generators. * <p>This method is only included for backwards compatibility. * The caller is encouraged to use one of the alternative * <code>getInstance</code> methods to obtain a SecureRandom object, and * then call the <code>generateSeed</code> method to obtain seed bytes * @param numBytes the number of seed bytes to generate. * @return the seed bytes. * Returns the given number of seed bytes, computed using the seed * generation algorithm that this class uses to seed itself. This * call may be used to seed other random number generators. * @param numBytes the number of seed bytes to generate. * @return the seed bytes. * Helper function to convert a long into a byte array (least significant for (
int i =
0; i <
8; i++) {
* Gets a default PRNG algorithm by looking through all registered * providers. Returns the first PRNG algorithm of the first provider that * has registered a SecureRandom implementation, or null if none of the * registered providers supplies a SecureRandom implementation. // Declare serialVersionUID to be compatible with JDK1.1 // Retain unused values serialized from JDK1.1 * We know that the MessageDigest class does not implement * java.io.Serializable. However, since this field is no longer * used, it will always be NULL and won't affect the serialization * of the SecureRandom class itself.