private void StartNfc_Click(object sender, EventArgs e)
{
text.Text = contactName;
// The `keys` array is used for pads and nfc exchange
// But GetBlockOfEntropyBytes destroys the data from the string builder,
// and we need a copy of it for calculating compression... so keep `key` and `keys`
key = EntropyManager.GetBlockOfEntropyBytes();
while (key != "__NO_ENTROPY__")
{
keys.Add(key);
key = EntropyManager.GetBlockOfEntropyBytes();
}
// Compute quality of entropy by running compression
string inputStr = key;
byte[] compressed; // output byte array after compression
using (var outStream = new MemoryStream())
{
using (var gzipStream = new GZipStream(outStream, CompressionMode.Compress))
using (var inStream = new MemoryStream(Encoding.UTF8.GetBytes(inputStr)))
inStream.CopyTo(gzipStream);
compressed = outStream.ToArray();
}
// Calculate compression ratio - use floats because % will be between 0-1, but we want the decimal accuracy
float compressionRatio = ((float)inputStr.Length - (float)compressed.Length) / (float)inputStr.Length;
// TODO: display compression ratio to user to indicate entropy quality
// NOTE: ^ lower compression = better! :: "Compression ratio: " + compressionRatio*100 + "%"
Toast.MakeText(ApplicationContext, "Compression ratio: " + compressionRatio * 100 + "%", ToastLength.Long).Show();
// NFC exchange
_nfcAdapter.SetNdefPushMessageCallback(this, this);
_nfcAdapter.SetOnNdefPushCompleteCallback(this, this);
text.Text = "Move Your Phone Near Your Friend's";
}
public void OnSensorChanged(SensorEvent e)
{
if (!recording)
{
return;
}
EntropyManager.FeedData(e.Sensor.Type, e.Values);
progStatus = (EntropyManager.GetSbSize() * 100) / EntropyManager.GetTotalSbSize();
RunOnUiThread(() =>
{
progBar.IncrementProgressBy(progStatus - oldStatus);
});
oldStatus = progStatus;
if (progBar.Progress >= 100)
{
finishedGen.Enabled = true;
text.Text = "Finished generating a set of keys";
_sensorManager.UnregisterListener(this);
}
}
