Get public key from byte [] / pem string - BouncyCastle C#

Question

I'm writing programm which communicates with SmartCard. The SmartCard is a source of Public Key. I get the public key as byte [] and convert it to String. I would like to use the key to create certificate signing request.

How can I transform byte[] / string (my public key) to any C# key parameters (e.g. RsaKeyParameters or AsymmetricKeyParameter)?

Answer 1

Here is a simple way to get X509Certificate from pem string:

pemString = pemString.Replace("-----BEGIN CERTIFICATE-----", "").Replace("-----END CERTIFICATE-----", "");
byte[] buffer = Convert.FromBase64String(pemString);
X509CertificateParser parser = new X509CertificateParser();
_certificate = parser.ReadCertificate(buffer);

When we have X509Certificate object we can get public key:

AsymmetricKeyParameter publicKey = certificate.GetPublicKey();

Answer 2

I found good explanation of my problem. Go here and read all answears. I have to put my bytes (public key) in proper ASN1 structure according to X.509 SubjectPublicKeyInfo/OpenSSL PEM public key format. Now I'm able to create AsymmetricKeyParameter.

    public static byte[] ConvertFromStringToHex(string inputHex)
    {
        inputHex = inputHex.Replace("-", "");

        byte[] resultantArray = new byte[inputHex.Length / 2];
        for (int i = 0; i < resultantArray.Length; i++)
        {
            resultantArray[i] = Convert.ToByte(inputHex.Substring(i * 2, 2), 16);
        }
        return resultantArray;
    }

    static void Main(string[] args)
    {
        var certObject = new Cryptography.CertificateManager();
        //AsymmetricKeyParameter privatekey = certObject.ReadCaPrivateKeyFromFile();
        string ASN1 = "";
        string prefix = "30 81 9F 30 0D 06 09 2A 86 48 86 F7 0D 01 01 01 05 00 03 81 8D 00 30 81 89 02 81 81 00 ";

        string suffix = " 02 03 01 00 01";
        string key = "96 33 A5 49 EB 9E 11 7F 73 3E 36 8C ED 73 D9 24 DC 8B DF A2 75 D3 E1 EA E9 44 BD 63 7A C1 D1 A6 E5 2E E5 64 55 AB FA C7 35 99 BF D1 CE 53 F3 E6 58 F8 DF 8A 6D CC 4C C9 98 5E 65 EA A2 5F 8C A3 43 6F 6C 08 D9 32 F7 29 4E 32 FE 4C 81 15 96 B7 AE B0 AE CE C2 07 C3 36 98 0B 90 4D EE 25 29 9A 56 4A 91 FE B6 C3 C0 BD 33 D4 BD 5F 33 0C 1F FF 93 D3 F3 EF 00 19 30 8F C0 7C B8 1C 0A AA A7 49";

        ASN1 = prefix + key + suffix;
        ASN1 = ASN1.Replace(" ", "");

        byte[] publicKeyByte = ConvertFromStringToHex(ASN1);
        string publicKeyBase64 = Convert.ToBase64String(publicKeyByte);

        AsymmetricKeyParameter publicKey = PublicKeyFactory.CreateKey(publicKeyByte);