public byte[] Encrypt(byte[] text, IKey key = null)
{
Validate(text, key);
ElgamalKey elgamalKey = key as ElgamalKey;
if (elgamalKey.IsPrivate)
{
throw new ArgumentException("Для шифрования нужен публичный ключ");
}
List <byte> result = new List <byte>(text.Length);
try
{
int readSize = elgamalKey.MaxOpenTextSize;
int writeSize = elgamalKey.MaxCipherTextSize;
BigInteger k = Helper.GenerateBigInteger(2, elgamalKey.Parameters.P - 3);
BigInteger r = BigInteger.ModPow(elgamalKey.Parameters.G, k, elgamalKey.Parameters.P);
byte[] packedBlock = new byte[writeSize];
byte[] rBlock = r.ToByteArray(false);
Buffer.BlockCopy(rBlock, 0, packedBlock, 0, rBlock.Length);
result.AddRange(packedBlock);
for (int currentByte = 0; currentByte < text.Length; currentByte += readSize)
{
int byteCopyCount = Math.Min(readSize, text.Length - currentByte);
byte[] currentBlock = new byte[byteCopyCount + 1]; // Добавлен 0х00 чтобы число было положительным
Buffer.BlockCopy(text, currentByte, currentBlock, 0, byteCopyCount);
BigInteger openInt = new BigInteger(currentBlock);
BigInteger cipherInt = BigInteger.ModPow(elgamalKey.Key, k, elgamalKey.Parameters.P);
BigInteger.DivRem(openInt * cipherInt, elgamalKey.Parameters.P, out cipherInt);
byte[] cipherBlock = cipherInt.ToByteArray(false);
packedBlock = new byte[writeSize];
Buffer.BlockCopy(cipherBlock, 0, packedBlock, 0, cipherBlock.Length);
result.AddRange(packedBlock);
}
}
catch (Exception ex)
{
throw new Exception("Ошибка! Проверьте входные параметры.", ex);
}
return(result.ToArray());
}
public void Decrypt(string inputPath, string outputPath, IKey key, Action <double> ProgressChanged = null)
{
if (key is ElgamalKey == false)
{
throw new ArgumentException("Key is not ElgamalKey");
}
ElgamalKey elgamalKey = key as ElgamalKey;
if (!elgamalKey.IsPrivate)
{
throw new ArgumentException("Для расшифровывания нужен закрытый ключ");
}
try
{
using FileStream instream = File.OpenRead(inputPath);
using FileStream outstream = File.Open(outputPath, FileMode.Create);
long fileSize = instream.Length;
int readSize = elgamalKey.MaxCipherTextSize * 1024 + elgamalKey.MaxCipherTextSize;
byte[] inputChunk = new byte[readSize];
int size = 0;
while ((size = instream.Read(inputChunk, 0, readSize)) != 0)
{
byte[] currentBlock;
if (size == readSize)
{
currentBlock = inputChunk;
}
else
{
currentBlock = new byte[size];
Buffer.BlockCopy(inputChunk, 0, currentBlock, 0, size);
}
byte[] outputChunk = Decrypt(currentBlock, elgamalKey);
outstream.Write(outputChunk, 0, outputChunk.Length);
int percent = ( int )((instream.Position * 100f) / fileSize);
ProgressChanged?.Invoke(percent);
}
}
catch (Exception ex)
{
throw new Exception("Ошибка! Проверьте входные параметры.", ex);
}
}
public byte[] Decrypt(byte[] ciphertext, IKey key = null)
{
Validate(ciphertext, key);
ElgamalKey elgamalKey = key as ElgamalKey;
if (!elgamalKey.IsPrivate)
{
throw new ArgumentException("Для расшифровывания нужен закрытый ключ");
}
List <byte> result = new List <byte>(ciphertext.Length);
try
{
int readSize = elgamalKey.MaxCipherTextSize;
int writeSize = elgamalKey.MaxOpenTextSize;
byte[] rBlock = new byte[readSize + 1];
Buffer.BlockCopy(ciphertext, 0, rBlock, 0, readSize);
BigInteger r = new BigInteger(rBlock);
BigInteger decryptConst = BigInteger.ModPow(r, elgamalKey.Parameters.P - 1 - elgamalKey.Key, elgamalKey.Parameters.P);
for (int currentByte = readSize; currentByte < ciphertext.Length; currentByte += readSize)
{
int byteCopyCount = Math.Min(readSize, ciphertext.Length - currentByte);
byte[] currentBlock = new byte[byteCopyCount + 1]; // Добавлен 0х00 чтобы число было положительным
Buffer.BlockCopy(ciphertext, currentByte, currentBlock, 0, byteCopyCount);
BigInteger cipherInt = new BigInteger(currentBlock);
BigInteger openInt;
BigInteger.DivRem(cipherInt * decryptConst, elgamalKey.Parameters.P, out openInt);
byte[] openBlock = openInt.ToByteArray(false);
byte[] packedBlock = new byte[writeSize];
Buffer.BlockCopy(openBlock, 0, packedBlock, 0, openBlock.Length);
result.AddRange(packedBlock);
}
}
catch (Exception ex)
{
throw new Exception("Ошибка! Проверьте входные параметры.", ex);
}
return(result.ToArray());
}
