fast encryption for a large unicode text file

I have a large unicode text file (35 MB) containing words separated by punctuation marks. I need to somehow hide the content of the file (at least from the majority of people who are not specialised in cracking).

The best way until now seemed like encryption. I know almost nothing about encryptio开发者_StackOverflow社区n. I tried to use the solution to a similar question "Simple 2 way encryption for C#" but it takes a long time to execute the encryption.

What is the fastest way (algorithm) that works out of the box (i.e. it is contained in the .Net lib)? A short example on how to use it would be nice :) I don't care how strong the encryption is, if you open the encrypted file with a text editor and don't see the words then it's perfect. The important part is speed.

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AES is pretty fast still, here's some help implementing it : Using AES encryption in C#

Anything other than industry standard Encryption is asking for problems sooner or later.

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What have you tried so far? Are standard encryptions like AES and blowfish too slow?

You can always do something simple like xor-ing the contents against some pass-code repeated to the same length as the file.

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As tilleryj said

xor-ing the contents against some pass-code repeated to the same length as the file is simple and fast

but it is les safe then other encription types. I wrote a simple class that helps you encript a string using another string as a password usig the xor method. hope some else can use it.

`using System;
using System.Text;


namespace MyEncriptionNameSpace
{
    class XorStringEncripter
    {
        private string __passWord;
        public XorStringEncripter(string password)
        {
            if (password.Length == 0)
            {
                throw new Exception("invalide password");
            }
            __passWord = password;
        }
        public string encript(string stringToEncript)
        {
            return __encript(stringToEncript);
        }

    public string decript(string encripTedString)
    {
        return __encript(encripTedString);
    }

    public string __encript(string stringToEncript)
    {
        var encriptedStringBuilder = new StringBuilder(stringToEncript.Length);
        int positionInPassword = 0;

        for (int i = 0; i < stringToEncript.Length; i++)
        {
            __corectPositionInPassWord(ref positionInPassword);
            encriptedStringBuilder.Append((char)((int)stringToEncript[i] ^ (int)__passWord[positionInPassword]));
            ++positionInPassword;
        }
        return encriptedStringBuilder.ToString();
    }

    private void __corectPositionInPassWord(ref int positionInPassword)
    {
        if (positionInPassword == __passWord.Length)
        {
            positionInPassword = 0;
        }
    }
}

}`

actualy encript and decript do the same thing , I provided bouth to avoid confusion on using the same function for bouth encription and decrition. This is because if you have a nuber A and you xor it with B and you obtain C then if you xor C and B you get A.
A xor B = C ---> C xor B = A