密码哈希 - 行业标准

Question

我知道可能已经有很多这样的问题了。但是，我真的没有找到我的问题的确切答案。

我知道密码存储在数据库中时带有 随机加盐 后跟散列密码。密码的值实际上是未知的（服务器和服务器管理员）。

什么是标准哈希算法？我知道 cryptography 是一个动态领域，会随着时间而变化。所以我想问一下当前的散列行业标准是什么。

我打算将其用于电子商务网站。所以密码存储安全其实很重要。

Answer 1

使用基于密码的密钥派生函数 (PBKDF) 根据（安全地）随机生成的盐 (PRNG) 和密码派生密钥，这是有关该主题的权威指南

https://www.owasp.org/index.php/Password_Storage_Cheat_Sheet

Answer 2

在问了同样的问题之后，我找到了密码散列和盐生成的解决方案。这是我在各种应用程序中使用的密码哈希方法的复制'n'粘贴。

如何存储生成的散列和盐将取决于您的应用程序和部署。

using System.Security;
using System.Security.Cryptography;        

    /// <summary>
    /// Generates a random salt value.
    /// </summary>
    /// <returns></returns>
    public string GenerateSaltValue()
    {
        //Generate a cryptographic random number.
        RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
        byte[] buff = new byte[64];
        rng.GetBytes(buff);

        // Return a Base64 string representation of the random number.
        return Convert.ToBase64String(buff);
    }

    /// <summary>
    /// Reccomended method to hash user passwords.
    /// <para>This hash is non-reversible and should use the GenerateSaltValue method for creating new salts.</para>
    /// </summary>
    /// <param name="plainText">The supplied password as a byte array</param>
    /// <param name="salt">The salt to use to create the hash.</param>
    /// <returns></returns>
    public byte[] HashPassword(byte[] plainText, byte[] salt)
    {
        HashAlgorithm algorithm = new SHA256Managed();

        byte[] plainTextWithSaltBytes =
          new byte[plainText.Length + salt.Length];

        for (int i = 0; i < plainText.Length; i++)
        {
            plainTextWithSaltBytes[i] = plainText[i];
        }
        for (int i = 0; i < salt.Length; i++)
        {
            plainTextWithSaltBytes[plainText.Length + i] = salt[i];
        }

        return algorithm.ComputeHash(plainTextWithSaltBytes);
    }

Answer 3

关于此主题的一些常用语言的首选参考是 https://crackstation.net/hashing-security.htm。我在下面复制了他们的代码示例的 C# 版本，但提供了其他语言

/* 
 * Password Hashing With PBKDF2 (http://crackstation.net/hashing-security.htm).
 * Copyright (c) 2013, Taylor Hornby
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, 
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation 
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Text;
using System.Security.Cryptography;

namespace PasswordHash
{
    /// <summary>
    /// Salted password hashing with PBKDF2-SHA1.
    /// Author: havoc AT defuse.ca
    /// www: http://crackstation.net/hashing-security.htm
    /// Compatibility: .NET 3.0 and later.
    /// </summary>
    public class PasswordHash
    {
        // The following constants may be changed without breaking existing hashes.
        public const int SALT_BYTE_SIZE = 24;
        public const int HASH_BYTE_SIZE = 24;
        public const int PBKDF2_ITERATIONS = 1000;

        public const int ITERATION_INDEX = 0;
        public const int SALT_INDEX = 1;
        public const int PBKDF2_INDEX = 2;

        /// <summary>
        /// Creates a salted PBKDF2 hash of the password.
        /// </summary>
        /// <param name="password">The password to hash.</param>
        /// <returns>The hash of the password.</returns>
        public static string CreateHash(string password)
        {
            // Generate a random salt
            RNGCryptoServiceProvider csprng = new RNGCryptoServiceProvider();
            byte[] salt = new byte[SALT_BYTE_SIZE];
            csprng.GetBytes(salt);

            // Hash the password and encode the parameters
            byte[] hash = PBKDF2(password, salt, PBKDF2_ITERATIONS, HASH_BYTE_SIZE);
            return PBKDF2_ITERATIONS + ":" +
                Convert.ToBase64String(salt) + ":" +
                Convert.ToBase64String(hash);
        }

        /// <summary>
        /// Validates a password given a hash of the correct one.
        /// </summary>
        /// <param name="password">The password to check.</param>
        /// <param name="correctHash">A hash of the correct password.</param>
        /// <returns>True if the password is correct. False otherwise.</returns>
        public static bool ValidatePassword(string password, string correctHash)
        {
            // Extract the parameters from the hash
            char[] delimiter = { ':' };
            string[] split = correctHash.Split(delimiter);
            int iterations = Int32.Parse(split[ITERATION_INDEX]);
            byte[] salt = Convert.FromBase64String(split[SALT_INDEX]);
            byte[] hash = Convert.FromBase64String(split[PBKDF2_INDEX]);

            byte[] testHash = PBKDF2(password, salt, iterations, hash.Length);
            return SlowEquals(hash, testHash);
        }

        /// <summary>
        /// Compares two byte arrays in length-constant time. This comparison
        /// method is used so that password hashes cannot be extracted from
        /// on-line systems using a timing attack and then attacked off-line.
        /// </summary>
        /// <param name="a">The first byte array.</param>
        /// <param name="b">The second byte array.</param>
        /// <returns>True if both byte arrays are equal. False otherwise.</returns>
        private static bool SlowEquals(byte[] a, byte[] b)
        {
            uint diff = (uint)a.Length ^ (uint)b.Length;
            for (int i = 0; i < a.Length && i < b.Length; i++)
                diff |= (uint)(a[i] ^ b[i]);
            return diff == 0;
        }

        /// <summary>
        /// Computes the PBKDF2-SHA1 hash of a password.
        /// </summary>
        /// <param name="password">The password to hash.</param>
        /// <param name="salt">The salt.</param>
        /// <param name="iterations">The PBKDF2 iteration count.</param>
        /// <param name="outputBytes">The length of the hash to generate, in bytes.</param>
        /// <returns>A hash of the password.</returns>
        private static byte[] PBKDF2(string password, byte[] salt, int iterations, int outputBytes)
        {
            Rfc2898DeriveBytes pbkdf2 = new Rfc2898DeriveBytes(password, salt);
            pbkdf2.IterationCount = iterations;
            return pbkdf2.GetBytes(outputBytes);
        }
    }
}

Answer 4

The value of the password is actually never known by the server

不完全正确。 Web 服务器必须知道密码。它被发布到 Web 服务器，并放入内存中。这没关系。重要的是 数据库服务器 永远不知道密码。在客户端上进行哈希处理无济于事，因为服务器控制 JavaScript 在客户端进行哈希处理！

没有 "standard" 哈希算法。要想选好，就选慢的。现在唯一好的选择是 PBKDF2、scrypt 和 bcrypt。

不是 MD5。不是 SHA。

哈希算法如果不够慢就毫无价值（或价值更低）。在您的生产服务器上散列密码应该需要大约 250 ms，这样它们在使用 GPU 进行离线攻击时仍然相当慢。

如果攻击者可以您的服务器未被发现，它们的价值就会降低。

如果您的用户使用易于猜测的密码（至少对于那些用户而言），它们就毫无价值。

密码哈希 - 行业标准

Password hashing - Industry Standards

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hash

passwords

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