Creating And Managing Digital Certificates In C# Using Visual Studio

How to Manage Certificate?

At this point, we successfully created a certificate in store named sampleCertStore.

Now, we can use our certificate from sampleCertStore to successfully sign and verify the data.

How to Sign Data?

Now, if Ahmed has to send the data to Fatima, he needs to sign the data with the private key.

To sign the data, he has to follow some simple steps, which are explained in the code snippet, given below. Once he signs the data, he should send both signature and data.

classX509CertTest {    
    staticvoid Main(string[] args) {    
        string messageToFatima = "My personal data";    
    
        //retrieve certificate from store//    
        X509Certificate2 certificate = GetCertFromStore();    
    
        //**signing data**//    
    
        //to sign we need the hash of data//    
        byte[] hashBytes = GetDataHash(messageToFatima);    
    
    
        byte[] signature = GetDigitalSignature(hashBytes);    
    }    
    
    
    privatestaticbyte[] GetDigitalSignature(byte[] hashBytes) {    
        X509Certificate2 certificate = GetCertFromStore();    
        /*use any asymmetric crypto service provider for encryption of hash   
        with private key of cert.   
        */    
        RSACryptoServiceProvider rsaCryptoService = (RSACryptoServiceProvider) certificate.PrivateKey;    
    
        /*now lets sign the hash   
        1.spevify hash bytes   
        2. and hash algorithm name to obtain the bytes   
        */    
        return rsaCryptoService.SignHash(hashBytes, CryptoConfig.MapNameToOID("SHA1"));    
    }    
    
    privatestaticbyte[] GetDataHash(string sampleData) {    
        //choose any hash algorithm    
        SHA1Managed managedHash = newSHA1Managed();    
    
        return managedHash.ComputeHash(Encoding.Unicode.GetBytes(sampleData));    
    }    
    
    privatestaticX509Certificate2 GetCertFromStore() {    
        //to access to store we need to specify store name and location    
        X509Store x509Store = newX509Store("sampleCertStore", StoreLocation.CurrentUser);    
    
        //obtain read only access to get cert    
        x509Store.Open(OpenFlags.ReadOnly);    
    
        return x509Store.Certificates[0];    
    }    
}     

How to Verify Data?

On other hand, when Fatima receives Ahmed’s message and the signature, she uses her public key to verify the message.

privatestaticbool VerifyData(byte[] signature, string messageFromAhemd)  
{  
    var messageHash = GetDataHash(messageFromAhemd);  
    X509Certificate2 certificate = GetCertFromStore();  
    RSACryptoServiceProvider cryptoServiceProvider = (RSACryptoServiceProvider) certificate.PublicKey.Key;  
    return cryptoServiceProvider.VerifyHash(messageHash, CryptoConfig.MapNameToOID("SHA1"), signature);  
}  

The complete source code is given below.

using System;    
using System.Security.Cryptography;    
using System.Security.Cryptography.X509Certificates;    
using System.Text;    
    
namespace CertTest {    
    classX509CertTest {    
        staticvoid Main(string[] args) {    
            string messageToFatima = "My personal data";    
    
            //retrieve certificate from store//    
            X509Certificate2 certificate = GetCertFromStore();    
    
            //**signing data**//    
    
            //to sign we need the hash of data//    
            byte[] hashBytes = GetDataHash(messageToFatima);    
    
    
            byte[] signature = GetDigitalSignature(hashBytes);    
            bool isVerified = VerifyData(signature, messageToFatima);    
    
            Console.WriteLine($ "IsVerified: {isVerified}");    
    
            Console.ReadLine();    
        }    
    
        privatestaticbool VerifyData(byte[] signature, string messageFromAhemd) {    
            var messageHash = GetDataHash(messageFromAhemd);    
    
            X509Certificate2 certificate = GetCertFromStore();    
    
            RSACryptoServiceProvider cryptoServiceProvider = (RSACryptoServiceProvider) certificate.PublicKey.Key;    
    
            return cryptoServiceProvider.VerifyHash(messageHash, CryptoConfig.MapNameToOID("SHA1"), signature);    
        }    
    
        privatestaticbyte[] GetDigitalSignature(byte[] hashBytes) {    
            X509Certificate2 certificate = GetCertFromStore();    
            /*use any asymmetric crypto service provider for encryption of hash   
            with private key of cert.   
            */    
            RSACryptoServiceProvider rsaCryptoService = (RSACryptoServiceProvider) certificate.PrivateKey;    
    
            /*now lets sign the hash   
            1.spevify hash bytes   
            2. and hash algorithm name to obtain the bytes   
            */    
            return rsaCryptoService.SignHash(hashBytes, CryptoConfig.MapNameToOID("SHA1"));    
        }    
    
        privatestaticbyte[] GetDataHash(string sampleData) {    
            //choose any hash algorithm    
            SHA1Managed managedHash = newSHA1Managed();    
    
            return managedHash.ComputeHash(Encoding.Unicode.GetBytes(sampleData));    
        }    
    
        privatestaticX509Certificate2 GetCertFromStore() {    
            //to access to store we need to specify store name and location    
            X509Store x509Store = newX509Store("sampleCertStore", StoreLocation.CurrentUser);    
    
            //obtain read only access to get cert    
            x509Store.Open(OpenFlags.ReadOnly);    
    
            return x509Store.Certificates[0];    
        }    
    }    
}