public byte[] Encrypt (byte[] rgb, bool fOAEP)
{
// choose between OAEP or PKCS#1 v.1.5 padding
AsymmetricKeyExchangeFormatter fmt = null;
if (fOAEP)
fmt = new RSAOAEPKeyExchangeFormatter (rsa);
else
fmt = new RSAPKCS1KeyExchangeFormatter (rsa);
return fmt.CreateKeyExchange (rgb);
}