/// <summary>
/// initialize page by AES key object
/// </summary>
/// <param name="aeskey">AES key object</param>
/// <param name="encrypted">encrypted text ready to decrypt</param>
public KeySetting(AESKey aeskey)
{
InitializeComponent();
Key = aeskey;
// mask AES key
string tKey = aeskey.Key.Substring(0, 26).PadRight(32, '*');
txt_key.Text = tKey;
txt_remark.Text = aeskey.Remark;
BackFromSetting = true;
}
/// <summary>
/// check clipboard content
/// </summary>
private async void CheckClipboard()
{
string text = await Clipboard.GetTextAsync();
string head = "UnderText://";
try
{
if (text.StartsWith(head))
{
text = text.Substring(text.IndexOf(head) + head.Length);
// get aes key encrypted by rsa public key
// then search key list
if (text.StartsWith("."))
{
byte[] data = Convert.FromBase64String(text.Substring(1));
string dec = Encoding.ASCII.GetString(rsaProvider.Decrypt(data, false));
if (AESKey.Validate(dec))
{
bool no_key = true;
foreach (var key in AESKeys)
{
if (key.Key.Equals(dec))
{
no_key = false;
break;
}
}
if (no_key)
{
AESKey newKey = new AESKey(dec);
AESKeys.Add(newKey);
await Navigation.PushAsync(new KeySetting(newKey));
}
}
}
// get rsa public key
// then generate aes key and send
else if (text.StartsWith(","))
{
string PK_recved = Encoding.ASCII.GetString(Convert.FromBase64String(text.Substring(1)));
if (!PK_recved.Equals(PK))
{
RSACryptoServiceProvider tRSAProvider = new RSACryptoServiceProvider(2048);
tRSAProvider.FromXmlString(PK_recved);
AESKey newKey = new AESKey(AESKey.Generate());
AESKeys.Add(newKey);
await Clipboard.SetTextAsync("UnderText://." + Convert.ToBase64String(tRSAProvider.Encrypt(Encoding.ASCII.GetBytes(newKey.Key), false)));
await DisplayAlert("Handshake(Step 2)", "AES packet has set to clipboard,\npaste and send the string to partner(s) who send you RSA packet,\nthen others will have the AES key.", "OK");
await Navigation.PushAsync(new KeySetting(newKey));
}
}
// get text data encrypted by aes key
// find right aes key in the list to decrypt
else
{
foreach (var key in AESKeys)
{
if (key.Decrypt(text) != string.Empty)
{
await Navigation.PushAsync(new KeySetting(key));
break;
}
}
}
}
}
catch
{
;
}
}