Replacement function for FormsAuthentication. HashPasswordForStoringInConfigFile

From .Net 4.5 version Microsoft deprecates the
System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile function which is used to create the hash of a string generally for password. Following is the extension method which gives the same output as FormsAuthentication.HashPasswordForStoringInConfigFile.

/// <summary>
/// Returns the hash of the given string. 
/// </summary>
/// <param name="stringToHash" />string for which the hash should be generated
/// <param name="hashAlgorithm" />Hash algorithm. Ex: MD5, SHA1, SHA256, SHA384, SHA512
/// <returns></returns>
public static string GetHash(this string stringToHash, string hashAlgorithm)
{
   var algorithm = System.Security.Cryptography.HashAlgorithm.Create(hashAlgorithm);
   byte[] hash = algorithm.ComputeHash(System.Text.Encoding.UTF8.GetBytes(stringToHash));

   // ToString("x2")  converts byte in hexadecimal value
   string encryptedVal = string.Concat(hash.Select(b => b.ToString("x2"))).ToUpperInvariant();
   return encryptedVal;
}

Happy Coding 😊!!

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Compute String Hash : C# Extension method

Hashing is the technique of transforming a string of characters into a shorter fixed-length value or key that represents the original string. Hashing is a one-way conversion. You cannot convert the hash value back to original string. So it is good to store sensitive data like passwords as hash value. MD5, SHA1, SHA256, SHA384, and SHA512 are the commonly used hashing algorithms.

.NET framework provides the classes to create the hash values in System.Security.Cryptography namespace. Following is the extension method to compute the hash value of a string using MD5, SHA1, SHA256, SHA384, and SHA512 algorithms

using System;
using System.Text;
using System.Security.Cryptography;
public static class Extensions
{
 public static string ComputeHash(this string data, string hashAlogorithm)
 {
  byte[] bytes = null;
  switch (hashAlogorithm.ToLower())
  {
   case "md5":
    using (MD5 md5Hash = MD5.Create())
    {
     bytes = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(data));
    }
    break;
   case "sha1":
    using (SHA1 sha1Hash = SHA1.Create())
    {
     bytes = sha1Hash.ComputeHash(Encoding.UTF8.GetBytes(data));
    }
    break;
   case "sha256":
    using (SHA256 sha256Hash = SHA256.Create())
    {
     bytes = sha256Hash.ComputeHash(Encoding.UTF8.GetBytes(data));
    }
    break;
   case "sha384":
    using (SHA384 sha384Hash = SHA384.Create())
    {
     bytes = sha384Hash.ComputeHash(Encoding.UTF8.GetBytes(data));
    }
    break;
   case "sha512":
    using (SHA512 sha512Hash = SHA512.Create())
    {
     bytes = sha512Hash.ComputeHash(Encoding.UTF8.GetBytes(data));
    }
    break;
  }
  
  if (bytes.Length > 0)
  {
   // Convert byte array to a string   
   StringBuilder builder = new StringBuilder();
   for (int i = 0; i < bytes.Length; i++)
   {
    builder.Append(bytes[i].ToString("x2"));
   }
   return builder.ToString();
  }
  else return null;
 }
}

Reference: https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography?view=netframework-4.8

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