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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *  http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.any23.util;
19  
20  import java.nio.charset.StandardCharsets;
21  import java.security.MessageDigest;
22  import java.security.NoSuchAlgorithmException;
23  
24  /**
25   * Mathematical utility functions.
26   *
27   * @author Michele Mostarda (mostarda@fbk.eu)
28   * @author Davide Palmisano (palmisano@fbk.eu)
29   */
30  public class MathUtils {
31  
32      private MathUtils() {
33      }
34  
35      /**
36       * <p>
37       * Create a MD5 <b>weak hash</b> for a given string.
38       * </p>
39       * <p>
40       * <b>N.B. This method MUST never be used in a sensitive context</b>. Examples of such usage include (i)
41       * User-password storage, (ii) Security token generation (used to confirm e-mail when registering on a website,
42       * reset password, etc...), (iii) To compute some message integrity.
43       * </p>
44       * Current usage is limited to {@link org.apache.any23.rdf.RDFUtils#getBNode(String)} which is fine for the creation
45       * of blank node(s).
46       *
47       * @param s
48       *            input string to create an MD5 hash for.
49       *
50       * @return a string representation of a MD5 {@link java.security.MessageDigest}
51       */
52      public static final String md5(String s) {
53          try {
54              MessageDigest md5 = MessageDigest.getInstance("MD5");
55              md5.reset();
56              md5.update(s.getBytes(StandardCharsets.UTF_8));
57              byte[] digest = md5.digest();
58              StringBuffer result = new StringBuffer();
59              for (byte b : digest) {
60                  result.append(Integer.toHexString(0xFF & b));
61              }
62              return result.toString();
63          } catch (NoSuchAlgorithmException e) {
64              throw new RuntimeException("Should never happen, MD5 is supported", e);
65          }
66      }
67  
68  }