RSA for big files

frozr · 03-20-2017, 08:37 PM

Pretty weird and old stuff i did, while being under drugs.

Code:
class RSAforbigfiles
    {
       public byte[] Encrypt(byte[] filetoencrypt, RSACryptoServiceProvider rsa )
        {
            int i;
            byte[] encryptedData;           
            int blockSize = (rsa.KeySize / 8) - 32;
            int rsablock= (rsa.KeySize / 8);
            byte[] dataToEncrypt = filetoencrypt;
            int repets = dataToEncrypt.Length / blockSize;
            byte[] dataaftercrypt = new byte[rsablock * (repets + 1)];
            byte[] buffer = new byte[blockSize];
            int lastblock = dataToEncrypt.Length - (repets * blockSize);
            for (i = 0; i < repets; i++)
            {
                Array.Copy(dataToEncrypt, blockSize * i, buffer, 0, blockSize);
                encryptedData = rsa.Encrypt(buffer, false);
                Array.Copy(encryptedData, 0, dataaftercrypt, rsablock * i, rsablock);
            }

            Array.Copy(dataToEncrypt, blockSize * (i), buffer, 0, lastblock);
            encryptedData = rsa.Encrypt(buffer, false);
            Array.Copy(encryptedData, 0, dataaftercrypt, rsablock * i, rsablock);
            return dataaftercrypt;
        }

        public byte[] Decrypt (byte[] filetoDecrypt, string privatekey, RSACryptoServiceProvider rsa)
        { 
            rsa.FromXmlString(privatekey);
            int blockSize = (rsa.KeySize / 8);
            byte[] dataToDencrypt = filetoDecrypt;
            int repets = dataToDencrypt.Length / blockSize - 1;
            byte[] decryptedBytes = new byte[dataToDencrypt.Length];
            byte[] buffer = new byte[blockSize];
            byte[] decryptedbuf;
            int decrlenght;
            Array.Copy(dataToDencrypt, buffer, blockSize);
            decryptedbuf = rsa.Decrypt(buffer, false);
            Array.Copy(decryptedbuf, decryptedBytes, decryptedbuf.Length);
            decrlenght = decryptedbuf.Length;
            for (int i = 1; i <= repets; i++)
            {
                Array.Copy(dataToDencrypt, blockSize * i, buffer, 0, blockSize);
                decryptedbuf = rsa.Decrypt(buffer, false);
                Array.Copy(decryptedbuf, 0, decryptedBytes, decrlenght, decryptedbuf.Length);
                decrlenght = decrlenght + decryptedbuf.Length;
            }
            byte[] orgfilemassive = new byte[decrlenght];
            Array.Copy(decryptedBytes, orgfilemassive, decrlenght);

            return orgfilemassive;
        }

    }

and example usage:
encryption

Code:
RSAforbigfiles RSA = new RSAforbigfiles();
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(4096);
            string privateKey = rsa.ToXmlString(true);
            string publicKey = rsa.ToXmlString(false);
            File.WriteAllText("rsaprivate.xml", privateKey);
File.WriteAllBytes(file, RSA.Encrypt (File.ReadAllBytes(file), rsa));

decryption

Code:
RSAforbigfiles RSA = new RSAforbigfiles();
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(4096);
            string keyString = File.ReadAllText(textBox1.Text);
  File.WriteAllBytes(file, RSA.Decrypt(File.ReadAllBytes(file), keyString, rsa));

just to be clear, this code are not used in FileFrozr

RSA for big files
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