need a help in order to Encrypt/decrypt file using bouncy castle in c#

please help;

i have creted a server application that generate a x.509v3 certificates. than, i export a publique and private key in .txt file ( format hex, or pem) ;

i must now encrypt files in another client application, my problem is that i can't do this using a public key directly , for this i have written a following code:

        string fichier = @"C:\\Users\\Me\\Documents\\marie.docx";
        FileInfo f = new FileInfo(fichier);


        byte[] buffer = new byte[(int)f.Length];

        System.IO.StreamReader strem = new System.IO.StreamReader(fichier);
        String line = strem.ReadToEnd();
        strem.Close();

        IBufferedCipher cipher = CipherUtilities.GetCipher("RSA/ECB/PKCS1Padding");

        string str = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA7cXmz0lTtzEuFAP0rR1f//RZZ8dGxa26I/LwJiNFqJULDvLjmiEHs+u+2gjc3Qm1cwcusuP+akCJIsGyn+9joEbEUKCaJOXbXsuqFKWFlsnfoCGTT8M1a5J2SNixsrLCim9P+qoGfml7JONUhWoiUVYqagRG4WgFmQHonttdnWEqk5yHtXp4ZzL+Bw54IaliyEzigBMW4k0rwMceR31MGnGGcplOynX6Ga5J3HZvLm2XoUQ6PAWw19yjmjiurwBugDOA2NdLOOR96Jxv39Kv/MyGXjjN3Z2hEsSVhHQ4j9RlEg0zsMhXoHJ/MsoVr5WKhEpCuuwp8IuQmwAFW1GoEwIDAQAB";

        char[] cArray = str.ToCharArray();
        byte[] pub_Array = new byte[cArray.Length];

        for (int j = 0; j < cArray.Length; j++)
            pub_Array[j] = (byte)cArray[j];

        KeyParameter par = new KeyParameter(pub_Array);

        cipher.Init(false, par);

        //byte[] output = cipher.DoFinal(data);

        int blockSize = cipher.GetBlockSize();

        int outputSize = cipher.GetOutputSize(buffer.Length);


        int leavedSize = buffer.Length % blockSize;
        int blocksSize = leavedSize != 0 ? buffer.Length / blockSize + 1 : buffer.Length / blockSize;
        byte[] raw = new byte[outputSize * blocksSize];
        int i = 0;

        while (buffer.Length - i * blockSize > 0)
        {
            if (buffer.Length - i * blockSize > blockSize)
                cipher.DoFinal(buffer, i * blockSize, blockSize,
                               raw, i * outputSize);
            else
                cipher.DoFinal(buffer, i * blockSize,
                               buffer.Length - i * blockSize,
                               raw, i * outputSize);
            i++;
        }

        // Ecriture du fichier chiffré sur le disque dur

        StreamWriter envfos = null;

        using (envfos = new StreamWriter("fichier_chiffrer.txt"))
        {
            envfos.Write(raw);

        }

        envfos.Close();

i have an

exception in : cipher.Init(false,par); << Impossible d'effectuer un cast d'un objet de type 'Org.BouncyCastle.Crypto.Parameters.KeyParameter' en type 'Org.BouncyCastle.Crypto.AsymmetricKeyParame开发者_运维技巧ter'.

Help please

any documentation in c# please;

think's in advance

Cordialement marie;

RSA encryption needs an AsymmeticKeyParameter as key. You can see the exception complain about that. You could use the RsaKeyParameter for this, but this will require you to supply 2 properties: Modulus and Exponent wich are both in the key.

Since you are using an already made X509 certificate you could also try to get the key from that file. I supplied some possible example code, but i don't know if it will work as i never even attemted to do something with X509 certificate. The code would replace your KeyParameter par = new KeyParameter(pub_Array); line.

X509CertificateParser parser = new X509CertificateParser();
AsymmeticKeyParameter par = parser.ReadCertificate(pub_array).GetPublicKey();

Here is a little snippet showing what is probably the easiest way to read the public key.

string str = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA7cXmz0lTtzEuFAP0rR1f//RZZ8dGxa26I/LwJiNFqJULDvLjmiEHs+u+2gjc3Qm1cwcusuP+akCJIsGyn+9joEbEUKCaJOXbXsuqFKWFlsnfoCGTT8M1a5J2SNixsrLCim9P+qoGfml7JONUhWoiUVYqagRG4WgFmQHonttdnWEqk5yHtXp4ZzL+Bw54IaliyEzigBMW4k0rwMceR31MGnGGcplOynX6Ga5J3HZvLm2XoUQ6PAWw19yjmjiurwBugDOA2NdLOOR96Jxv39Kv/MyGXjjN3Z2hEsSVhHQ4j9RlEg0zsMhXoHJ/MsoVr5WKhEpCuuwp8IuQmwAFW1GoEwIDAQAB";
string header = "-----BEGIN PUBLIC KEY\n";
string trailer = "\n-----END PUBLIC KEY";
str = header + str + trailer;
StringReader sr = new StringReader(str);
PemReader PemRdr = new PemReader(sr);
RsaKeyParameters KeyParams = (RsaKeyParameters)PemRdr.ReadObject();