How to use thumbprint for security?

Question

I am using RSACryptoServiceProvider for security.

I built the code using a self signed certificate for testing purposes. not user has provided us with the actual thumbprint. I was expecting to get a certificate instead ? how do i use the Thumbprint ?

here is the code:

/// Builds Authorization in using self signed certificate
/// </summary>
/// <returns></returns>
private string BuildAuthorization()
{
    X509Certificate2 cert = GetCertificate();

    RSACryptoServiceProvider provideEncryptor = (RSACryptoServiceProvider)cert.PublicKey.Key;

    string authorizaionValue = string.Format("{0}:{1}:{2}", _userName,_password, _currentTime);

    byte[] encryptedData = provideEncryptor.Encrypt(Encoding.UTF8.GetBytes(authorizaionValue), false);

    string encryptedString = Convert.ToBase64String(encryptedData);

    return encryptedString;

}


/// <summary>
/// creates a self signed certificate 
/// </summary>
/// <returns></returns>
private X509Certificate2 GetCertificate()
{
    X509Store store = new X509Store(StoreLocation.CurrentUser);
    store.Open(OpenFlags.ReadOnly);
    X509Certificate2 cert = null;
    string certName = ConfigurationManager.AppSettings["CertName"];

    foreach (var c in store.Certificates)
    {
        if (c.Subject.Equals(certName, StringComparison.OrdinalIgnoreCase))
        {
            cert = c;
            break;
        }
    }


    store.Close();

    return cert;

}

the thumbprint provided is something like :

87aa7f6********************9b2d95093a6

Answer 1

A thumbprint is just an identifier of a certificate, usually an MD5 or SHA1 hash of the certificate.

You cannot really do anything with the thumbprint itself, think of it as an ID of a record in a database. You will need to sure, but what I suspect the intention is they are giving your the thumbprint of a certificate that is in the certificate store. This StackOverflow question provides information on how to load a certificate from the certificate store by thumbprint.