[Solved] AES encryption on file over 1GB

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You are reading the entire file at the start of the method:

byte[] bytesToBeEncrypted = File.ReadAllBytes(file);

This is causing the OutOfMemoryException. Here’s an idea of how you’d do this:

static void EncryptFile(string file, string password)
{
    byte[] passwordBytes = Encoding.UTF8.GetBytes(password);
    byte[] salt = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };

    passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

    RijndaelManaged AES = new RijndaelManaged();
    AES.KeySize = AES.LegalKeySizes[0].MaxSize;
    AES.BlockSize = AES.LegalBlockSizes[0].MaxSize;
    AES.Padding = PaddingMode.PKCS7;

    //"What it does is repeatedly hash the user password along with the salt." High iteration counts.
    using (var key = new Rfc2898DeriveBytes(passwordBytes, salt, 1000)) // automatically dispose key
    {
        AES.Key = key.GetBytes(AES.KeySize / 8);
        AES.IV = key.GetBytes(AES.BlockSize / 8);
        AES.Mode = CipherMode.CFB;
    }
    using (FileStream fsCrypt = new FileStream(file + ".enc", FileMode.Create)) // automatically dispose fsCrypt
    {
        //write salt to the beginning of the output file, so in this case can be random every time
        fsCrypt.Write(salt, 0, salt.Length);
    }

    int bytesToRead = 128 * 1024 * 1024; // 128MB 
    byte[] buffer = new byte[bytesToRead]; // create the array that will be used encrypted
    long fileOffset = 0;
    int read = 0;
    bool allRead = false;

    while (!allRead)
    {
       using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
       {
           fs.Seek(fileOffset, SeekOrigin.Begin); // continue reading from where we were...
           read = fs.Read(buffer, 0, bytesToRead); // read the next chunk
       }

       if (read == 0)
           allRead = true;
       else
           fileOffset += read;

       using (FileStream fsCrypt = new FileStream(file + ".enc", FileMode.Open)) // automatically dispose fsCrypt
       {
           using (CryptoStream cs = new CryptoStream(fsCrypt, AES.CreateEncryptor(), CryptoStreamMode.Write))
           {
               fsCrypt.Seek(fileOffset, SeekOrigin.End);
               cs.Write(buffer, 0, read);
           }
        }
    }

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solved AES encryption on file over 1GB