/// <summary>
/// Encrypts the data using the public key
/// </summary>
/// <param name="value"></param>
/// <param name="publicKey"></param>
/// <returns></returns>
public static string Encrypt(byte[] valueBytes, string publicKey)
{
// use rsa to encrypt the key
using (var rsa = new RSACryptoServiceProvider())
{
rsa.FromXmlString(publicKey);
// for large keys use symmetric encryption, and then just use RSA to encrypt the key.
if (valueBytes.Length > 50)
{
// generate a symmetric new key.
byte[] key = new byte[20];
using (var randomNumberGenerator = RandomNumberGenerator.Create())
{
randomNumberGenerator.GetBytes(key);
}
var encryptedBytes = EncryptString.Encrypt(valueBytes, key);
var encryptedKey = rsa.Encrypt(key, true);
// combine the rsa and encrypted bytes.
// the combined string contains length (4 bytes), encryptedKey (length), encryptedBytes (remainder)
var combinedValue = new byte[4 + encryptedKey.Length + encryptedBytes.Length];
Array.Copy(BitConverter.GetBytes(encryptedKey.Length), combinedValue, 4);
Array.Copy(encryptedKey, 0, combinedValue, 4, encryptedKey.Length);
Array.Copy(encryptedBytes, 0, combinedValue, 4 + encryptedKey.Length, encryptedBytes.Length);
return(Convert.ToBase64String(combinedValue));
}
else
{
var encryptedValue = rsa.Encrypt(valueBytes, true);
var combinedValue = new byte[4 + encryptedValue.Length];
Array.Copy(ZeroBytes, 0, combinedValue, 0, 4);
Array.Copy(encryptedValue, 0, combinedValue, 4, encryptedValue.Length);
return(Convert.ToBase64String(combinedValue));
}
}
}
