X509 Certificates 2

 

Scenario:

Use X509 Certificates 2 for encryption/decryption

Solution:

•  makecert -r -pe -n "CN=CERT_SIGN_TEST_CERT" -b 08/13/2021 -e 08/15/2021 -sky exchange -ss my
• -r  - Creates a self-signed certificate.
• -pe - Mark private key as exportable. 
• -n - Name [X.500 standard]
• -b - Start date
• -e - End Date
• -sky - Subject's key specification [Signature/Exchange]
• -ss - SubjectCertStoreName
• MMC -> File->Add/Remove Snap-in -> Certificates -> Personal -> Certificates -> CERT_SIGN_TEST_CERT -> ThumbPrint

 
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class ProgramX509Certificate2
    {
        static void Main(string[] args)
        {
            var originalData = "This is top secret!!!!";
            var thumbPrint = "c6aedff377b3c970b3447c3319241111e1188";
            X509Certificate2 cert = GetCertificate(thumbPrint);

            if (cert == null)
            {
                Console.WriteLine("Certificate 'CN=CERT_SIGN_TEST_CERT' not found.");
                Console.ReadLine();
            }

            var encryptData = Encrypt(thumbPrint, originalData);

            var decryptData = Decrypt(thumbPrint, encryptData);

            Console.WriteLine($"Message is: {decryptData}");
            Console.ReadLine();
        }

        private static X509Certificate2 GetCertificate(string thumbprint)
        {
            var store = new X509Store(StoreName.My, StoreLocation.CurrentUser);
            store.Open(OpenFlags.ReadOnly);

            var cert = store.Certificates.Cast<X509Certificate2>()
                .FirstOrDefault(
                    c => c.Thumbprint.Equals(thumbprint.Replace(" ", "").ToUpper(), StringComparison.InvariantCultureIgnoreCase));
            return cert;
        }

        private static RSA GetPublicKey(string thumbprint)
        {
            var cert = GetCertificate(thumbprint);
            return (RSA)cert.PublicKey.Key;
        }

        private static RSA GetPrivateKey(string thumbprint)
        {
            var cert = GetCertificate(thumbprint);
            return (RSA)cert.GetRSAPrivateKey();
        }

        private static string Encrypt(string thumbprint, string value)
        {
            var encryptData = GetPublicKey(thumbprint).Encrypt(System.Text.Encoding.UTF8.GetBytes(value), RSAEncryptionPadding.Pkcs1);
            return Convert.ToBase64String(encryptData);
        }

        private static string Decrypt(string thumbprint, string value)
        {
            var decrypttData = GetPrivateKey(thumbprint).Decrypt(Convert.FromBase64String(value), RSAEncryptionPadding.Pkcs1);
            return System.Text.Encoding.UTF8.GetString(decrypttData);
        }
    }