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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  }