public static string DecryptEncryptedFile(EncryptedFileParameters @params)
{
//========================================================================
// Decrypt encrypted symmetric key with private key.
var rsa = EncryptController.ImportPrivateKey(Directory.GetCurrentDirectory() +
$"/../../CurrentUsers/{AccountsController.GetInstance().CurrentAccount.Username}.key");
var symmetricKey =
Encoding.Unicode.GetString(rsa.Decrypt(Convert.FromBase64String(@params.EncryptedSymmetricKey), false));
//========================================================================
// Decrypt encrypted sendername.
var decryptedName = Cipher.Decrypt(@params.EncryptedSenderName, symmetricKey, @params.SymmetricAlgorithm);
//========================================================================
// Validate sender and receiver certificate.
var senderAccount = AccountsController.GetInstance().Accounts[decryptedName];
var senderCertificate = new X509Certificate2();
senderCertificate.Import(senderAccount.PathToCertificate);
var receiverAccount = AccountsController.GetInstance().CurrentAccount;
var receiverCertificate = new X509Certificate2();
receiverCertificate.Import(receiverAccount.PathToCertificate);
if (!ValidateController.ValidateCertificates(receiverCertificate))
{
return("");
}
if (!ValidateController.ValidateCertificates(senderCertificate))
{
return("");
}
//========================================================================
// Decrypt digital signature with symmetric key.
var digitalSignature = Convert.FromBase64String(
Cipher.Decrypt(@params.EncryptedSignature, symmetricKey, @params.SymmetricAlgorithm));
//========================================================================
// Decrypt data with symmetric key.
var decryptedData = Cipher.Decrypt(@params.EncryptedData, symmetricKey, @params.SymmetricAlgorithm);
//========================================================================
// Verify messagehash with signature.
var decryptedHashAlg = Cipher.Decrypt(@params.EncryptedHashAlg, symmetricKey, @params.SymmetricAlgorithm);
var rsaCrypto = (RSACryptoServiceProvider)senderCertificate.PublicKey.Key;
if (!VerifyData(Encoding.Unicode.GetBytes(decryptedData), digitalSignature, rsaCrypto.ExportParameters(false), decryptedHashAlg))
{
return(null);
}
//========================================================================
// Return a message.
return(decryptedData);
}
public static EncryptedFileParameters EncryptedFileParametersParser(string path)
{
var ext = Path.GetExtension(path);
SymmetricAlgorithm symmetricAlgorithm;
switch (ext)
{
case ".aes":
symmetricAlgorithm = Aes.Create();
break;
case ".des3":
symmetricAlgorithm = TripleDES.Create();
break;
case ".rc2":
symmetricAlgorithm = RC2.Create();
break;
default:
symmetricAlgorithm = Aes.Create();
break;
}
var content = File.ReadAllText(path);
var match = Regex.Match(content,
"ENCRYPTED SYMMETRIC KEY:\n(.*?)\n\n" +
"ENCRYPTED HASH ALGORITHM:\n(.*?)\n\n" +
"ENCRYPTED FILE SENDER:\n(.*?)\n\n" +
"ENCRYPTED DIGITAL SIGNATURE:\n(.*?)\n\n" +
"ENCRYPTED FILENAME\n(.*?)\n\n" +
"ENCRYPTED FILE:\n(.*?)\n\n");
var @params = new EncryptedFileParameters
{
EncryptedSymmetricKey = match.Groups[1].Value,
EncryptedHashAlg = match.Groups[2].Value,
EncryptedName = match.Groups[3].Value,
EncryptedSignature = match.Groups[4].Value,
EncryptedFileName = match.Groups[5].Value,
EncryptedData = match.Groups[6].Value,
SymmetricAlgorithm = symmetricAlgorithm
};
return(@params);
}
public static EncryptedFileParameters EncryptedFileParametersParser(string path, object locker)
{
var ext = Path.GetExtension(path);
ext = ext?.Substring(1);
SymmetricAlgorithm symmetricAlgorithm = EncryptController.CheckSymmetricAlgorithm(ext);
string content;
while (true)
{
try
{
FileStream fileStream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
content = File.ReadAllText(path);
fileStream.Close();
break;
}
catch (Exception)
{
Thread.Sleep(200);
}
}
var match = Regex.Match(content,
"ENCRYPTED SYMMETRIC KEY:\n(.*?)\n\n" +
"ENCRYPTED HASH ALGORITHM:\n(.*?)\n\n" +
"ENCRYPTED DATA SENDER:\n(.*?)\n\n" +
"ENCRYPTED DIGITAL SIGNATURE:\n(.*?)\n\n" +
"ENCRYPTED DATA:\n(.*?)\n\n");
var @params = new EncryptedFileParameters
{
EncryptedSymmetricKey = match.Groups[1].Value,
EncryptedHashAlg = match.Groups[2].Value,
EncryptedSenderName = match.Groups[3].Value,
EncryptedSignature = match.Groups[4].Value,
EncryptedData = match.Groups[5].Value,
SymmetricAlgorithm = symmetricAlgorithm
};
return(@params);
}
public static string DecryptEncryptedFile(EncryptedFileParameters @params)
{
//========================================================================
// Decrypt encrypted symmetric key with private key.
var rsa = EncryptController.ImportPrivateKey(Directory.GetCurrentDirectory() +
"/../../CurrentUser/private.key");
var symmetricKey =
Encoding.Unicode.GetString(rsa.Decrypt(Convert.FromBase64String(@params.EncryptedSymmetricKey), false));
//========================================================================
// Decrypt encrypted sender and filename.
var decryptedName = Cipher.Decrypt(@params.EncryptedName, symmetricKey, @params.SymmetricAlgorithm);
//========================================================================
// Validate sender and receiver certificate.
var senderAccount = AccountsController.GetInstance().Accounts[decryptedName];
var senderCertificate = new X509Certificate2();
senderCertificate.Import(senderAccount.PathToCertificate);
var receiverAccount = AccountsController.GetInstance().CurrentAccount;
var receiverCertificate = new X509Certificate2();
receiverCertificate.Import(receiverAccount.PathToCertificate);
if (!ValidateController.ValidateCertificates(receiverCertificate))
{
return("");
}
if (!ValidateController.ValidateCertificates(senderCertificate))
{
return("");
}
//========================================================================
// Decrypt digital signature with symmetric key.
var digitalSignature = Convert.FromBase64String(
Cipher.Decrypt(@params.EncryptedSignature, symmetricKey, @params.SymmetricAlgorithm));
//========================================================================
// Decrypt file with symmetric key.
var decryptedFileName = Cipher.Decrypt(@params.EncryptedFileName, symmetricKey, @params.SymmetricAlgorithm);
var decryptedFile = Encoding.Unicode.GetBytes(
Cipher.Decrypt(@params.EncryptedData, symmetricKey, @params.SymmetricAlgorithm));
//========================================================================
// Verify filehash with signature.
var decryptedHashAlg = Cipher.Decrypt(@params.EncryptedHashAlg, symmetricKey, @params.SymmetricAlgorithm);
var rsaCrypto = (RSACryptoServiceProvider)senderCertificate.PublicKey.Key;
if (!VerifyData(decryptedFile, digitalSignature, rsaCrypto.ExportParameters(false), decryptedHashAlg))
{
MessageBox.Show("File is changed! Unsuccessfully decrypt. 😐");
return("");
}
//========================================================================
// Write file on filesystem.
var parentPath = Directory.GetCurrentDirectory() + "/../../DecryptedMessages";
var currentUsername = AccountsController.GetInstance().CurrentAccount.Username;
var path = $"{parentPath}/{currentUsername}/{decryptedName}/{Path.GetFileName(decryptedFileName)}";
if (!Directory.Exists($"{parentPath}/{currentUsername}/{decryptedName}/"))
{
Directory.CreateDirectory($"{parentPath}/{currentUsername}/{decryptedName}/");
}
File.WriteAllBytes(path, decryptedFile);
return(path);
}
