Secure Hash : hashCode « Class Definition « Java Tutorial






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 * JBoss DNA (http://www.jboss.org/dna)
 * See the COPYRIGHT.txt file distributed with this work for information
 * regarding copyright ownership.  Some portions may be licensed
 * to Red Hat, Inc. under one or more contributor license agreements.
 * See the AUTHORS.txt file in the distribution for a full listing of 
 * individual contributors. 
 *
 * JBoss DNA is free software. Unless otherwise indicated, all code in JBoss DNA
 * is licensed to you under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * JBoss DNA is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * @author Randall Hauch
 */
public class SecureHash {

    /**
     * Commonly-used hashing algorithms.
     */
    public enum Algorithm {
        MD2("MD2", "The MD2 message digest algorithm as defined in RFC 1319"),
        MD5("MD5", "The MD5 message digest algorithm as defined in RFC 1321"),
        SHA_1("SHA-1", "The Secure Hash Algorithm, as defined in Secure Hash Standard, NIST FIPS 180-1"),
        SHA_256(
                "SHA-256",
                "New hash algorithms for which the draft Federal Information Processing Standard 180-2, "
                + "Secure Hash Standard (SHS) is now available.  SHA-256 is a 256-bit hash function intended to provide 128 bits of "
                + "security against collision attacks."),
        SHA_384(
                "SHA-384",
                "New hash algorithms for which the draft Federal Information Processing Standard 180-2, "
                + "Secure Hash Standard (SHS) is now available.  A 384-bit hash may be obtained by truncating the SHA-512 output."),
        SHA_512(
                "SHA-512",
                "New hash algorithms for which the draft Federal Information Processing Standard 180-2, "
                + "Secure Hash Standard (SHS) is now available.  SHA-512 is a 512-bit hash function intended to provide 256 bits of security.");
        private String name;
        private String description;

        private Algorithm( String name,
                           String description ) {
            this.name = name;
            this.description = description;
        }

        public String digestName() {
            return this.name;
        }

        public String description() {
            return this.description;
        }

        @Override
        public String toString() {
            return digestName();
        }
    }

    /**
     * Get the hash of the supplied content, using the supplied digest algorithm.
     * 
     * @param algorithm the hashing function algorithm that should be used
     * @param content the content to be hashed; may not be null
     * @return the hash of the contents as a byte array
     * @throws NoSuchAlgorithmException if the supplied algorithm could not be found
     * @throws IllegalArgumentException if the algorithm is null
     */
    public static byte[] getHash( Algorithm algorithm,
                                  byte[] content ) throws NoSuchAlgorithmException {

        return getHash(algorithm.digestName(), content);
    }

    /**
     * Get the hash of the supplied content, using the supplied digest algorithm.
     * 
     * @param algorithm the hashing function algorithm that should be used
     * @param file the file containing the content to be hashed; may not be null
     * @return the hash of the contents as a byte array
     * @throws NoSuchAlgorithmException if the supplied algorithm could not be found
     * @throws IllegalArgumentException if the algorithm is null
     * @throws IOException if there is an error reading the file
     */
    public static byte[] getHash( Algorithm algorithm,
                                  File file ) throws NoSuchAlgorithmException, IOException {

        return getHash(algorithm.digestName(), file);
    }

    /**
     * Get the hash of the supplied content, using the supplied digest algorithm.
     * 
     * @param algorithm the hashing function algorithm that should be used
     * @param stream the stream containing the content to be hashed; may not be null
     * @return the hash of the contents as a byte array
     * @throws NoSuchAlgorithmException if the supplied algorithm could not be found
     * @throws IllegalArgumentException if the algorithm is null
     * @throws IOException if there is an error reading the stream
     */
    public static byte[] getHash( Algorithm algorithm,
                                  InputStream stream ) throws NoSuchAlgorithmException, IOException {

        return getHash(algorithm.digestName(), stream);
    }

    /**
     * Get the hash of the supplied content, using the digest identified by the supplied name.
     * 
     * @param digestName the name of the hashing function (or {@link MessageDigest message digest}) that should be used
     * @param content the content to be hashed; may not be null
     * @return the hash of the contents as a byte array
     * @throws NoSuchAlgorithmException if the supplied algorithm could not be found
     */
    public static byte[] getHash( String digestName,
                                  byte[] content ) throws NoSuchAlgorithmException {
        MessageDigest digest = MessageDigest.getInstance(digestName);
        assert digest != null;
        return digest.digest(content);
    }

    /**
     * Get the hash of the supplied content, using the digest identified by the supplied name.
     * 
     * @param digestName the name of the hashing function (or {@link MessageDigest message digest}) that should be used
     * @param file the file whose content is to be hashed; may not be null
     * @return the hash of the contents as a byte array
     * @throws NoSuchAlgorithmException if the supplied algorithm could not be found
     * @throws IOException if there is an error reading the file
     */
    public static byte[] getHash( String digestName,
                                  File file ) throws NoSuchAlgorithmException, IOException {

        MessageDigest digest = MessageDigest.getInstance(digestName);
        assert digest != null;
        InputStream in = new BufferedInputStream(new FileInputStream(file));
        boolean error = false;
        try {
            int bufSize = 1024;
            byte[] buffer = new byte[bufSize];
            int n = in.read(buffer, 0, bufSize);
            int count = 0;
            while (n != -1) {
                count += n;
                digest.update(buffer, 0, n);
                n = in.read(buffer, 0, bufSize);
            }
        } catch (IOException e) {
            error = true;
            throw e;
        } finally {
            try {
                in.close();
            } catch (IOException e) {
                if (!error) throw e;
            }
        }
        return digest.digest();
    }

    /**
     * Get the hash of the supplied content, using the digest identified by the supplied name. Note that this method never closes
     * the supplied stream.
     * 
     * @param digestName the name of the hashing function (or {@link MessageDigest message digest}) that should be used
     * @param stream the stream containing the content to be hashed; may not be null
     * @return the hash of the contents as a byte array
     * @throws NoSuchAlgorithmException if the supplied algorithm could not be found
     * @throws IOException if there is an error reading the stream
     */
    public static byte[] getHash( String digestName,
                                  InputStream stream ) throws NoSuchAlgorithmException, IOException {

        MessageDigest digest = MessageDigest.getInstance(digestName);
        assert digest != null;
        int bufSize = 1024;
        byte[] buffer = new byte[bufSize];
        int n = stream.read(buffer, 0, bufSize);
        int count = 0;
        while (n != -1) {
            count += n;
            digest.update(buffer, 0, n);
            n = stream.read(buffer, 0, bufSize);
        }
        return digest.digest();
    }
}








5.34.hashCode
5.34.1.Implement hashCode using commons-lang
5.34.2.Comparing Object Values Using Hash Codes
5.34.3.Get the identity hash codes
5.34.4.Null Safe Hash Code
5.34.5.Secure Hash
5.34.6.Get hash code for primitive data types
5.34.7.A very efficient java hash algorithm, based on the BuzHash algoritm
5.34.8.Computing hash codes
5.34.9.Returns an integer hash code representing the given double array value.