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August 4, 2017 11:34
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/////////////////////////////////////////////////////////////////////////////// | |
// SAMPLE: Hashing data with salt using MD5 and several SHA algorithms. | |
// | |
// To run this sample, create a new Visual C# project using the Console | |
// Application template and replace the contents of the Class1.cs file with | |
// the code below. | |
// | |
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, | |
// EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED | |
// WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE. | |
// | |
// Copyright (C) 2002 Obviex(TM). All rights reserved. | |
// | |
using System; | |
using System.Text; | |
using System.Security.Cryptography; | |
/// <summary> | |
/// This class generates and compares hashes using MD5, SHA1, SHA256, SHA384, | |
/// and SHA512 hashing algorithms. Before computing a hash, it appends a | |
/// randomly generated salt to the plain text, and stores this salt appended | |
/// to the result. To verify another plain text value against the given hash, | |
/// this class will retrieve the salt value from the hash string and use it | |
/// when computing a new hash of the plain text. Appending a salt value to | |
/// the hash may not be the most efficient approach, so when using hashes in | |
/// a real-life application, you may choose to store them separately. You may | |
/// also opt to keep results as byte arrays instead of converting them into | |
/// base64-encoded strings. | |
/// </summary> | |
public class SimpleHash | |
{ | |
/// <summary> | |
/// Generates a hash for the given plain text value and returns a | |
/// base64-encoded result. Before the hash is computed, a random salt | |
/// is generated and appended to the plain text. This salt is stored at | |
/// the end of the hash value, so it can be used later for hash | |
/// verification. | |
/// </summary> | |
/// <param name="plainText"> | |
/// Plaintext value to be hashed. The function does not check whether | |
/// this parameter is null. | |
/// </param> | |
/// <param name="hashAlgorithm"> | |
/// Name of the hash algorithm. Allowed values are: "MD5", "SHA1", | |
/// "SHA256", "SHA384", and "SHA512" (if any other value is specified | |
/// MD5 hashing algorithm will be used). This value is case-insensitive. | |
/// </param> | |
/// <param name="saltBytes"> | |
/// Salt bytes. This parameter can be null, in which case a random salt | |
/// value will be generated. | |
/// </param> | |
/// <returns> | |
/// Hash value formatted as a base64-encoded string. | |
/// </returns> | |
public static string ComputeHash(string plainText, | |
string hashAlgorithm, | |
byte[] saltBytes) | |
{ | |
// If salt is not specified, generate it on the fly. | |
if (saltBytes == null) | |
{ | |
// Define min and max salt sizes. | |
int minSaltSize = 4; | |
int maxSaltSize = 8; | |
// Generate a random number for the size of the salt. | |
Random random = new Random(); | |
int saltSize = random.Next(minSaltSize, maxSaltSize); | |
// Allocate a byte array, which will hold the salt. | |
saltBytes = new byte[saltSize]; | |
// Initialize a random number generator. | |
RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider(); | |
// Fill the salt with cryptographically strong byte values. | |
rng.GetNonZeroBytes(saltBytes); | |
} | |
// Convert plain text into a byte array. | |
byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText); | |
// Allocate array, which will hold plain text and salt. | |
byte[] plainTextWithSaltBytes = | |
new byte[plainTextBytes.Length + saltBytes.Length]; | |
// Copy plain text bytes into resulting array. | |
for (int i=0; i < plainTextBytes.Length; i++) | |
plainTextWithSaltBytes[i] = plainTextBytes[i]; | |
// Append salt bytes to the resulting array. | |
for (int i=0; i < saltBytes.Length; i++) | |
plainTextWithSaltBytes[plainTextBytes.Length + i] = saltBytes[i]; | |
// Because we support multiple hashing algorithms, we must define | |
// hash object as a common (abstract) base class. We will specify the | |
// actual hashing algorithm class later during object creation. | |
HashAlgorithm hash; | |
// Make sure hashing algorithm name is specified. | |
if (hashAlgorithm == null) | |
hashAlgorithm = ""; | |
// Initialize appropriate hashing algorithm class. | |
switch (hashAlgorithm.ToUpper()) | |
{ | |
case "SHA1": | |
hash = new SHA1Managed(); | |
break; | |
case "SHA256": | |
hash = new SHA256Managed(); | |
break; | |
case "SHA384": | |
hash = new SHA384Managed(); | |
break; | |
case "SHA512": | |
hash = new SHA512Managed(); | |
break; | |
default: | |
hash = new MD5CryptoServiceProvider(); | |
break; | |
} | |
// Compute hash value of our plain text with appended salt. | |
byte[] hashBytes = hash.ComputeHash(plainTextWithSaltBytes); | |
// Create array which will hold hash and original salt bytes. | |
byte[] hashWithSaltBytes = new byte[hashBytes.Length + | |
saltBytes.Length]; | |
// Copy hash bytes into resulting array. | |
for (int i=0; i < hashBytes.Length; i++) | |
hashWithSaltBytes[i] = hashBytes[i]; | |
// Append salt bytes to the result. | |
for (int i=0; i < saltBytes.Length; i++) | |
hashWithSaltBytes[hashBytes.Length + i] = saltBytes[i]; | |
// Convert result into a base64-encoded string. | |
string hashValue = Convert.ToBase64String(hashWithSaltBytes); | |
// Return the result. | |
return hashValue; | |
} | |
/// <summary> | |
/// Compares a hash of the specified plain text value to a given hash | |
/// value. Plain text is hashed with the same salt value as the original | |
/// hash. | |
/// </summary> | |
/// <param name="plainText"> | |
/// Plain text to be verified against the specified hash. The function | |
/// does not check whether this parameter is null. | |
/// </param> | |
/// <param name="hashAlgorithm"> | |
/// Name of the hash algorithm. Allowed values are: "MD5", "SHA1", | |
/// "SHA256", "SHA384", and "SHA512" (if any other value is specified, | |
/// MD5 hashing algorithm will be used). This value is case-insensitive. | |
/// </param> | |
/// <param name="hashValue"> | |
/// Base64-encoded hash value produced by ComputeHash function. This value | |
/// includes the original salt appended to it. | |
/// </param> | |
/// <returns> | |
/// If computed hash mathes the specified hash the function the return | |
/// value is true; otherwise, the function returns false. | |
/// </returns> | |
public static bool VerifyHash(string plainText, | |
string hashAlgorithm, | |
string hashValue) | |
{ | |
// Convert base64-encoded hash value into a byte array. | |
byte[] hashWithSaltBytes = Convert.FromBase64String(hashValue); | |
// We must know size of hash (without salt). | |
int hashSizeInBits, hashSizeInBytes; | |
// Make sure that hashing algorithm name is specified. | |
if (hashAlgorithm == null) | |
hashAlgorithm = ""; | |
// Size of hash is based on the specified algorithm. | |
switch (hashAlgorithm.ToUpper()) | |
{ | |
case "SHA1": | |
hashSizeInBits = 160; | |
break; | |
case "SHA256": | |
hashSizeInBits = 256; | |
break; | |
case "SHA384": | |
hashSizeInBits = 384; | |
break; | |
case "SHA512": | |
hashSizeInBits = 512; | |
break; | |
default: // Must be MD5 | |
hashSizeInBits = 128; | |
break; | |
} | |
// Convert size of hash from bits to bytes. | |
hashSizeInBytes = hashSizeInBits / 8; | |
// Make sure that the specified hash value is long enough. | |
if (hashWithSaltBytes.Length < hashSizeInBytes) | |
return false; | |
// Allocate array to hold original salt bytes retrieved from hash. | |
byte[] saltBytes = new byte[hashWithSaltBytes.Length - | |
hashSizeInBytes]; | |
// Copy salt from the end of the hash to the new array. | |
for (int i=0; i < saltBytes.Length; i++) | |
saltBytes[i] = hashWithSaltBytes[hashSizeInBytes + i]; | |
// Compute a new hash string. | |
string expectedHashString = | |
ComputeHash(plainText, hashAlgorithm, saltBytes); | |
// If the computed hash matches the specified hash, | |
// the plain text value must be correct. | |
return (hashValue == expectedHashString); | |
} | |
} | |
/// <summary> | |
/// Illustrates the use of the SimpleHash class. | |
/// </summary> | |
public class SimpleHashTest | |
{ | |
/// <summary> | |
/// The main entry point for the application. | |
/// </summary> | |
[STAThread] | |
static void Main(string[] args) | |
{ | |
string password = "myP@5sw0rd"; // original password | |
string wrongPassword = "password"; // wrong password | |
string passwordHashMD5 = | |
SimpleHash.ComputeHash(password, "MD5", null); | |
string passwordHashSha1 = | |
SimpleHash.ComputeHash(password, "SHA1", null); | |
string passwordHashSha256 = | |
SimpleHash.ComputeHash(password, "SHA256", null); | |
string passwordHashSha384 = | |
SimpleHash.ComputeHash(password, "SHA384", null); | |
string passwordHashSha512 = | |
SimpleHash.ComputeHash(password, "SHA512", null); | |
Console.WriteLine("COMPUTING HASH VALUES\r\n"); | |
Console.WriteLine("MD5 : {0}", passwordHashMD5); | |
Console.WriteLine("SHA1 : {0}", passwordHashSha1); | |
Console.WriteLine("SHA256: {0}", passwordHashSha256); | |
Console.WriteLine("SHA384: {0}", passwordHashSha384); | |
Console.WriteLine("SHA512: {0}", passwordHashSha512); | |
Console.WriteLine(""); | |
Console.WriteLine("COMPARING PASSWORD HASHES\r\n"); | |
Console.WriteLine("MD5 (good): {0}", | |
SimpleHash.VerifyHash( | |
password, "MD5", | |
passwordHashMD5).ToString()); | |
Console.WriteLine("MD5 (bad) : {0}", | |
SimpleHash.VerifyHash( | |
wrongPassword, "MD5", | |
passwordHashMD5).ToString()); | |
Console.WriteLine("SHA1 (good): {0}", | |
SimpleHash.VerifyHash( | |
password, "SHA1", | |
passwordHashSha1).ToString()); | |
Console.WriteLine("SHA1 (bad) : {0}", | |
SimpleHash.VerifyHash( | |
wrongPassword, "SHA1", | |
passwordHashSha1).ToString()); | |
Console.WriteLine("SHA256 (good): {0}", | |
SimpleHash.VerifyHash( | |
password, "SHA256", | |
passwordHashSha256).ToString()); | |
Console.WriteLine("SHA256 (bad) : {0}", | |
SimpleHash.VerifyHash( | |
wrongPassword, "SHA256", | |
passwordHashSha256).ToString()); | |
Console.WriteLine("SHA384 (good): {0}", | |
SimpleHash.VerifyHash( | |
password, "SHA384", | |
passwordHashSha384).ToString()); | |
Console.WriteLine("SHA384 (bad) : {0}", | |
SimpleHash.VerifyHash( | |
wrongPassword, "SHA384", | |
passwordHashSha384).ToString()); | |
Console.WriteLine("SHA512 (good): {0}", | |
SimpleHash.VerifyHash( | |
password, "SHA512", | |
passwordHashSha512).ToString()); | |
Console.WriteLine("SHA512 (bad) : {0}", | |
SimpleHash.VerifyHash( | |
wrongPassword, "SHA512", | |
passwordHashSha512).ToString()); | |
} | |
} | |
// | |
// END OF FILE | |
/////////////////////////////////////////////////////////////////////////////// |
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