private byte[] ValidateHmac(byte[] encryptedData)
{
byte[] validatedHmac = null;
if (encryptedData != null)
{
var hmacByteLength = Options.HmacSize / 8;
if (encryptedData.Length > hmacByteLength)
{
var startIndex = encryptedData.Length - hmacByteLength;
var dataLength = encryptedData.Length - hmacByteLength;
var hmac = new byte[hmacByteLength];
var hmacData = new byte[dataLength];
Buffer.BlockCopy(encryptedData, 0, hmacData, 0, dataLength);
Buffer.BlockCopy(encryptedData, startIndex, hmac, 0, hmacByteLength);
var isValid = HmacProvider.ValidateHmac(Options.HmacKey, hmacData, hmac);
if (isValid)
{
validatedHmac = hmacData;
}
}
}
return(validatedHmac);
}
private byte[] HmacEncryptedData(byte[] encryptedData)
{
byte[] encryptedHmac = null;
if (encryptedData != null)
{
using (var memoryStream = new MemoryStream())
{
memoryStream.Write(encryptedData, 0, encryptedData.Length);
var hmac = HmacProvider.CalculateHash(Options.HmacKey, memoryStream.ToArray());
if (hmac != null)
{
memoryStream.Write(hmac, 0, hmac.Length);
encryptedHmac = memoryStream.ToArray();
}
}
}
return(encryptedHmac);
}