Override default HashAlgorithm.Create()

Question

I've been trying to override the default value from SHA1 to SHA256 of what System.Security.Cryptography.HashAlgorithm.Create() returns. Based off the docs, it is supposed to be override-able.

I came across this article, but it seems to only mention mapping a custom hash algorithm to override one of the existing ones. I want to just override the default of SHA1 to a default of SHA256.

Is that possible using the article above?

Something like this?

<configuration>  
   <mscorlib>  
      <cryptographySettings>  
         <cryptoNameMapping>    
            <nameEntry name="System.Security.Cryptography.HashAlgorithm"  
                       class="System.Security.Cryptography.SHA256"/>  
         </cryptoNameMapping>  
      </cryptographySettings>  
   </mscorlib>  
</configuration>

Answer 1

Yes, it's possible.

If you need to apply new default hash algorithm in every running .NET Framework application on machine just write this section inside machine.config file:

<mscorlib>  
    <cryptographySettings>  
        <cryptoNameMapping>  
            <cryptoClasses>  
                <cryptoClass DefaultHashAlgorithm="System.Security.Cryptography.SHA256Managed, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>  
            </cryptoClasses>
            <nameEntry name="System.Security.Cryptography.HashAlgorithm"  
                    class="DefaultHashAlgorithm"/>  
        </cryptoNameMapping>  
    </cryptographySettings>  
</mscorlib>  

Note that machine.config file placed here:

x32:

%windir%\Microsoft.NET\Framework\[version]\config\machine.config

x64:

%windir%\Microsoft.NET\Framework64\[version]\config\machine.config 

Also you can change default algorithm on every built-in hash algorithm by change DefaultHashAlgorithm attribute. See list of algorithms here.