Calculate a MD5 hash from a string

I use the following C# code to calculate a MD5 hash from a string. It works well and generates a 32-character hex string like this: 900150983cd24fb0d6963f7d28e17f72

string sSourceData;
byte[] tmpSource;
byte[] tmpHash;
sSourceData = "MySourceData";

//Create a byte array from source data.
tmpSource = ASCIIEncoding.ASCII.GetBytes(sSourceData);
tmpHash = new MD5CryptoServiceProvider().ComputeHash(tmpSource);

// and then convert tmpHash to string...

Is there a way to use code like this to generate a 16-character hex string (or 12-character string)? A 32-character hex string is good but I think it'll be boring for the customer to enter the code!

As per MSDN

Create MD5:

public static string CreateMD5(string input)
{
    // Use input string to calculate MD5 hash
    using (System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create())
    {
        byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(input);
        byte[] hashBytes = md5.ComputeHash(inputBytes);

        return Convert.ToHexString(hashBytes); // .NET 5 +

        // Convert the byte array to hexadecimal string prior to .NET 5
        // StringBuilder sb = new System.Text.StringBuilder();
        // for (int i = 0; i < hashBytes.Length; i++)
        // {
        //     sb.Append(hashBytes[i].ToString("X2"));
        // }
        // return sb.ToString();
    }
}

// given, a password in a string
string password = @"1234abcd";

// byte array representation of that string
byte[] encodedPassword = new UTF8Encoding().GetBytes(password);

// need MD5 to calculate the hash
byte[] hash = ((HashAlgorithm) CryptoConfig.CreateFromName("MD5")).ComputeHash(encodedPassword);

// string representation (similar to UNIX format)
string encoded = BitConverter.ToString(hash)
   // without dashes
   .Replace("-", string.Empty)
   // make lowercase
   .ToLower();

// encoded contains the hash you want

Was trying to create a string representation of MD5 hash using LINQ, however, none of the answers were LINQ solutions, therefore adding this to the smorgasbord of available solutions.

string result;
using (MD5 hash = MD5.Create())
{
    result = String.Join
    (
        "",
        from ba in hash.ComputeHash
        (
            Encoding.UTF8.GetBytes(observedText)
        ) 
        select ba.ToString("x2")
    );
}

You can use Convert.ToBase64String to convert 16 byte output of MD5 to a ~24 char string. A little bit better without reducing security. (j9JIbSY8HuT89/pwdC8jlw== for your example)

Depends entirely on what you are trying to achieve. Technically, you could just take the first 12 characters from the result of the MD5 hash, but the specification of MD5 is to generate a 32 char one.

Reducing the size of the hash reduces the security, and increases the chance of collisions and the system being broken.

Perhaps if you let us know more about what you are trying to achieve we may be able to assist more.

I suppose it is better to use UTF-8 encoding in the string MD5.

public static string MD5(this string s)
{
    using var provider = System.Security.Cryptography.MD5.Create();        
    StringBuilder builder = new StringBuilder();                           

    foreach (byte b in provider.ComputeHash(Encoding.UTF8.GetBytes(s)))
        builder.Append(b.ToString("x2").ToLower());

    return builder.ToString();        
}

Support string and file stream.

examples

string hashString = EasyMD5.Hash("My String");

string hashFile = EasyMD5.Hash(System.IO.File.OpenRead("myFile.txt"));

-

   class EasyMD5
        {
            private static string GetMd5Hash(byte[] data)
            {
                StringBuilder sBuilder = new StringBuilder();
                for (int i = 0; i < data.Length; i++)
                    sBuilder.Append(data[i].ToString("x2"));
                return sBuilder.ToString();
            }
    
            private static bool VerifyMd5Hash(byte[] data, string hash)
            {
                return 0 == StringComparer.OrdinalIgnoreCase.Compare(GetMd5Hash(data), hash);
            }
    
            public static string Hash(string data)
            {
                using (var md5 = MD5.Create())
                    return GetMd5Hash(md5.ComputeHash(Encoding.UTF8.GetBytes(data)));
            }
            public static string Hash(FileStream data)
            {
                using (var md5 = MD5.Create())
                    return GetMd5Hash(md5.ComputeHash(data));
            }
    
            public static bool Verify(string data, string hash)
            {
                using (var md5 = MD5.Create())
                    return VerifyMd5Hash(md5.ComputeHash(Encoding.UTF8.GetBytes(data)), hash);
            }
    
            public static bool Verify(FileStream data, string hash)
            {
                using (var md5 = MD5.Create())
                    return VerifyMd5Hash(md5.ComputeHash(data), hash);
            }
        }

public static string Md5(string input, bool isLowercase = false)
{
    using (var md5 = MD5.Create())
    {
        var byteHash = md5.ComputeHash(Encoding.UTF8.GetBytes(input));
        var hash = BitConverter.ToString(byteHash).Replace("-", "");
        return (isLowercase) ? hash.ToLower() : hash;
    }
}

This solution requires c# 8 and takes advantage of Span<T>. Note, you would still need to call .Replace("-", string.Empty).ToLowerInvariant() to format the result if necessary.

public static string CreateMD5(ReadOnlySpan<char> input)
{
    var encoding = System.Text.Encoding.UTF8;
    var inputByteCount = encoding.GetByteCount(input);
    using var md5 = System.Security.Cryptography.MD5.Create();

    Span<byte> bytes = inputByteCount < 1024
        ? stackalloc byte[inputByteCount]
        : new byte[inputByteCount];
    Span<byte> destination = stackalloc byte[md5.HashSize / 8];

    encoding.GetBytes(input, bytes);

    // checking the result is not required because this only returns false if "(destination.Length < HashSizeValue/8)", which is never true in this case
    md5.TryComputeHash(bytes, destination, out int _bytesWritten);

    return BitConverter.ToString(destination.ToArray());
}

Idk anything about 16 character hex strings....

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

But here is mine for creating MD5 hash in one line.

string hash = BitConverter.ToString(MD5.Create().ComputeHash(Encoding.ASCII.GetBytes("THIS STRING TO MD5"))).Replace("-","");

Here is my utility function for UTF8, which can be replaced with ASCII if desired:

    public static byte[] MD5Hash(string message)
    {
        return MD5.Create().ComputeHash(Encoding.UTF8.GetBytes(message));
    }

A MD5 hash is 128 bits, so you can't represent it in hex with less than 32 characters...

System.Text.StringBuilder hash = new System.Text.StringBuilder();
        System.Security.Cryptography.MD5CryptoServiceProvider md5provider = new System.Security.Cryptography.MD5CryptoServiceProvider();
        byte[] bytes = md5provider.ComputeHash(new System.Text.UTF8Encoding().GetBytes(YourEntryString));

        for (int i = 0; i < bytes.Length; i++)
        {
            hash.Append(bytes[i].ToString("x2")); //lowerCase; X2 if uppercase desired
        }
        return hash.ToString();

A faster alternative of existing answer for .NET Core 2.1 and higher:

public static string CreateMD5(string s)
{
    using (System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create())
    {
        var encoding = Encoding.ASCII;
        var data = encoding.GetBytes(s);
              
        Span<byte> hashBytes = stackalloc byte[16];
        md5.TryComputeHash(data, hashBytes, out int written);
        if(written != hashBytes.Length)
            throw new OverflowException();


        Span<char> stringBuffer = stackalloc char[32];
        for (int i = 0; i < hashBytes.Length; i++)
        {
            hashBytes[i].TryFormat(stringBuffer.Slice(2 * i), out _, "x2");
        }
        return new string(stringBuffer);
    }
}

You can optimize it even more if you are sure that your strings are small enough and replace encoding.GetBytes by unsafe int GetBytes(ReadOnlySpan chars, Span bytes) alternative.

Extending Anant Dabhi's answer

a helper method:

using System.Text;

namespace XYZ.Helpers
{
    public static class EncryptionHelper
    {
        public static string ToMD5(this string input)
        {
            // Use input string to calculate MD5 hash
            using (System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create())
            {
                byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(input);
                byte[] hashBytes = md5.ComputeHash(inputBytes);

                // Convert the byte array to hexadecimal string
                StringBuilder sb = new StringBuilder();
                for (int i = 0; i < hashBytes.Length; i++)
                {
                    sb.Append(hashBytes[i].ToString("X2"));
                }
                return sb.ToString();
            }
        }
    }
}

https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography.md5?view=netframework-4.7.2

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

    static string GetMd5Hash(string input)
            {
                using (MD5 md5Hash = MD5.Create())
                {
    
                    // Convert the input string to a byte array and compute the hash.
                    byte[] data = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(input));
    
                    // Create a new Stringbuilder to collect the bytes
                    // and create a string.
                    StringBuilder sBuilder = new StringBuilder();
    
                    // Loop through each byte of the hashed data 
                    // and format each one as a hexadecimal string.
                    for (int i = 0; i < data.Length; i++)
                    {
                        sBuilder.Append(data[i].ToString("x2"));
                    }
    
                    // Return the hexadecimal string.
                    return sBuilder.ToString();
                }
            }
    
            // Verify a hash against a string.
            static bool VerifyMd5Hash(string input, string hash)
            {
                // Hash the input.
                string hashOfInput = GetMd5Hash(input);
    
                // Create a StringComparer an compare the hashes.
                StringComparer comparer = StringComparer.OrdinalIgnoreCase;
    
                return 0 == comparer.Compare(hashOfInput, hash);
              
            }

I'd like to offer an alternative that appears to perform at least 10% faster than craigdfrench's answer in my tests (.NET 4.7.2):

public static string GetMD5Hash(string text)
{
    using ( var md5 = MD5.Create() )
    {
        byte[] computedHash = md5.ComputeHash( Encoding.UTF8.GetBytes(text) );
        return new System.Runtime.Remoting.Metadata.W3cXsd2001.SoapHexBinary(computedHash).ToString();
    }
}

If you prefer to have using System.Runtime.Remoting.Metadata.W3cXsd2001; at the top, the method body can be made an easier to read one-liner:

using ( var md5 = MD5.Create() )
{
    return new SoapHexBinary( md5.ComputeHash( Encoding.UTF8.GetBytes(text) ) ).ToString();
}

Obvious enough, but for completeness, in OP's context it would be used as:

sSourceData = "MySourceData";
tmpHash = GetMD5Hash(sSourceData);

StringBuilder sb= new StringBuilder();
for (int i = 0; i < tmpHash.Length; i++)
{
   sb.Append(tmpHash[i].ToString("x2"));
}

    public static string GetMD5(string encryptString)
    {
        var passByteCrypt = new MD5CryptoServiceProvider().ComputeHash(Encoding.UTF8.GetBytes(encryptString));

        return ByteArrayToString(passByteCrypt);
    }
    public static string ByteArrayToString(byte[] bytes)
    {
        var output = new StringBuilder(bytes.Length);

        foreach (var t in bytes)
        {
            output.Append(t.ToString("X2"));
        }

        return output.ToString().ToLower();
    }

this is simple md5 ByteCrypt

Here is a condensed version.

private string CreateMD5(string myText)
{
    var hash = System.Security.Cryptography.MD5.Create()
        .ComputeHash(System.Text.Encoding.ASCII.GetBytes(myText ?? ""));
    return string.Join("", Enumerable.Range(0, hash.Length).Select(i => hash[i].ToString("x2")));
}

If you are using a version lower than .NET5 this is a neat way to write it

string.Concat(yourHashBytes.Select(x => x.ToString("X2")))