One-way encryption methods

Question

This is just a theoretical question. I am in the process of programming a huge multi-server / multi-client network view.

Question:
What are the possible methods of irreversible encryption or aka one-way encryption? And what is the most appropriate to implement in my case and in .NET?

Can someone provide me with a list of method names?

Answer 1

byte[] data = new byte[DATA_SIZE]; byte[] result; SHA256 shaM = new SHA256Managed(); result = shaM.ComputeHash(data); 

Here is an overview and here is a namespace with standard features. Just look at the HashAlgorithm and its descendants.

Answer 2

Mostly you want to use MD5 or SHA-256. Oh, and FYI, if so, this is called a hash. The MSDN documentation covers both hashes broadly.

Answer 3

As others have mentioned, md5 and sha are hashing algorithms that can be used for this. One thing to consider before choosing one is how important it is for it to be decrypted (hashes cannot be decrypted in the normal sense of the word). MD5 and SHA are designed to work quickly, which means that creating rainbow tables ( http://en.wikipedia.org/wiki/Rainbow_tables ) with lots of hashes will also be fast. With the speed of modern GPUs, hundreds of millions of hashes can be generated every second, which means you can quickly redirect the efforts of MD5 and SHA.

If you store things like a password, it is best to use a hashing algorithm that should be slow, like bcrypt ( http://bcrypt.codeplex.com/ )

Answer 4

For new visitors to this question, crackstation.net has a full .NET implementation below , as well as a fairly detailed explanation of what you should do and how it all works.

The following code is copied unchanged from crackstation.net

 /* * 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); } } } 

A few notes:

• OWASP source post and recommendations suggest stronger encryption using HMAC
• The iterative score in the above implementation is probably a bit lower. OWASP and this answer offer their own balancing workload
• The salt size in the implementation above is set to 24, but if I read this answer , then it should not exceed 20. This says that I am nothing but an expert in the field of cryptography, so I can’t say whether this statement is true or false.