public static string Decrypt(string CipherText, string mod, string exp)
{
var Modulus = HelperFunctions.FromHexToByte(mod);
var Exponent = HelperFunctions.FromHexToByte(exp);
var CipherTextBytes = Convert.FromBase64String(CipherText);
var modulus = new BigInteger(1, Modulus);
var exponent = new BigInteger(1, Exponent);
var Parameters = new RsaKeyParameters(true, modulus, exponent);
var RSAengine = new RsaEngine();
RSAengine.Init(false, Parameters);
var blockSize = RSAengine.GetInputBlockSize();
var output = new List <byte>();
for (var chunkPosition = 0; chunkPosition < CipherTextBytes.Length; chunkPosition += blockSize)
{
var chunkSize = Math.Min(blockSize, CipherTextBytes.Length - chunkPosition * blockSize);
output.AddRange(RSAengine.ProcessBlock(CipherTextBytes, chunkPosition, chunkSize));
}
var output2 = output.ToArray();
var PlainText = Encoding.ASCII.GetString(output2);
return(PlainText);
}
public static void CheckDigitalSignature_FromString(string text, string signatureFile, string RSApublicKeyFile, TextBox outputTextBox, HashingMode mode)
{
var signature = FileManager.Read_Signature(signatureFile);
var publicKey = FileManager.Read_RSAKey(RSApublicKeyFile);
var signatureBytes = HelperFunctions.FromHexToByte(signature);
var decoded = RSA.Decrypt(Convert.ToBase64String(signatureBytes), publicKey.Modulus, publicKey.Exponent);
var hash = SHA.Hash(text, mode);
outputTextBox.Text = hash == decoded ? "Potpis je valjan!" : "Potpis nije valjan!";
}
public static void OpenDigitalEnvelope(string envelopeFile, string RSAprivateKey, string outputFile, EncryptionMode mode, SymetricAlgorithm algorithm)
{
var envelope = FileManager.Read_Envelope(envelopeFile);
var privateKey = FileManager.Read_RSAKey(RSAprivateKey);
var keyCipher = Convert.ToBase64String(HelperFunctions.FromHexToByte(envelope.Key));
var key = RSA.Decrypt(keyCipher, privateKey.Modulus, privateKey.Exponent);
var input = Convert.FromBase64String(envelope.Data);
var keyBytes = HelperFunctions.FromHexToByte(key);
var vector = FileManager.ReadFile_IVector("IVector.txt");
var data = algorithm == SymetricAlgorithm.THREE_DES ? THREE_DES.Decrypt(input, keyBytes, mode) : AES.Decrypt(input, keyBytes, vector, mode);
var envelopeText = Encoding.ASCII.GetString(data);
FileManager.Write(envelopeText, outputFile);
}
public static byte[] ReadFile_IVector(string file)
{
var vectorFile = new StreamReader(Program.Direktorij + file);
string currentLine;
var vector = "";
while (vectorFile.ReadLine() != "Initialization vector:")
{
}
while ((currentLine = vectorFile.ReadLine()) != "---END OS2 CRYPTO DATA---" && currentLine != "")
{
vector += currentLine?.Substring(4);
}
var vectorBytes = HelperFunctions.FromHexToByte(vector);
return(vectorBytes);
}