Encrypt large files in c#

Question

Please help me modify this code to encrypt/decrypt in blocks instead of huge byte arrays! the code that converts the file and calls the encryption class is:

Console.Write("Enter File Path: ");
docPath = Console.ReadLine();
extension = docPath.Substring(docPath.IndexOf(".")).Trim();
byte[] binarydata = File.ReadAllBytes(docPath);
text = System.Convert.ToBase64String(binarydata, 0, binarydata.Length);
var Encrypted = AESCryptography.Encrypt(text, m.ToString(), extension);
using (FileStream fs = File.Create(docPath.Substring(0,docPath.IndexOf(".")) + ".aent"))
{
    Byte[] info = new UTF8Encoding(true).GetBytes(Encrypted);
    // Add some information to the file.
    fs.Write(info, 0, info.Length);
}

And the class that does the actual encryption is this:

public static class AESCryptography
{
    private const int keysize = 256;
    public static string Encrypt(string plainText, string passPhrase, string extention)
    {
        byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
        using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
        {
            byte[] keyBytes = password.GetBytes(keysize / 8);
            using (RijndaelManaged symmetricKey = new RijndaelManaged())
            {
                symmetricKey.GenerateIV();
                symmetricKey.Mode = CipherMode.CBC;
                using (ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, symmetricKey.IV))
                {
                    using (MemoryStream memoryStream = new MemoryStream())
                    {
                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                        {
                            cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                            cryptoStream.FlushFinalBlock();
                            byte[] cipherTextBytes = memoryStream.ToArray();
                            return Convert.ToBase64String(cipherTextBytes) + "\n" + Convert.ToBase64String(symmetricKey.IV) + "\n" + extention;
                        }
                    }
                }
            }
        }
    }

    public static string Decrypt(string cipherText, string passPhrase, string initVector)
    {
        byte[] initVectorBytes = Convert.FromBase64String(initVector);
        byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
        using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
        {
            byte[] keyBytes = password.GetBytes(keysize / 8);
            using (RijndaelManaged symmetricKey = new RijndaelManaged())
            {
                symmetricKey.Mode = CipherMode.CBC;
                using (ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes))
                {
                    using (MemoryStream memoryStream = new MemoryStream(cipherTextBytes))
                    {
                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
                        {
                            byte[] plainTextBytes = new byte[cipherTextBytes.Length];
                            int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
                            return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
                        }
                    }
                }
            }
        }
    }
}

I need the encryption class to be able to encrypt files as big as ~2.5GB. I have tried multiple times, most didn't work others didn't even encrypt! Please Help! I need to present this tomorrow!

This is not a duplicate. The answer provided there answered that question. here I am not asking how to optimize memory consumption instead I am asking for help in implementing that answer — javaseaayameradost, Aug 21 '14 at 11:14
There are many examples: _____ http://support.microsoft.com/kb/307010 ______ http://stackoverflow.com/questions/9237324/encrypting-decrypting-large-files-net — , Aug 21 '14 at 12:05

score 1 · Answer 1 · edited May 23 '17 at 12:14

You can 'chain' streams to encrypt large files, so you don't need to hold them in memory.

See answer from anton-gogolev https://stackoverflow.com/a/38629596/1776231 for question AES-Encrypt-then-MAC a large file with .NET

using(var encryptedFileStream = File.OpenWrite("..."))        
using(var macCryptoStream = new CryptoStream(encryptedFileStream, mac, CryptoStreamMode.Write))
using(var encryptCryptoStream = new CryptoStream(macCryptoStream, encryptor, CryptoStreamMode.Write))
using(var inputFileStream = File.OpenRead("..."))
    inputFileStream.CopyTo(encryptCryptoStream);

Encrypt large files in c#

1 Answers1