Sequence of Uncompressed Data

Question

I would like to create an “incompressible” data sequence from X MBytes through an algorithm. I want to create a program that measures network speed through a VPN connection (avoiding the built-in vpn compression).

Can someone help me? Thank!

PS. I need an algorithm, I used a compressed file to such an extent that it can no longer be compressed, but now I need to generate a data sequence from scratch programmatically.

Answer 1

White noise data is truly random and therefore incompressible.

Therefore, you should find an algorithm that generates it (or an approximation).

Try this on Linux:

# dd if=/dev/urandom bs=1024 count=10000 2>/dev/null | bzip2 -9 -c -v > /dev/null
(stdin): 0.996:1, 8.035 bits/byte, -0.44% saved, 10240000 in, 10285383 out.

, ...

Answer 2

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Answer 3

:  1.  2. , ​​ AES ( )

Algo

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Answer 4

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Answer 5

(C/POSIX) , . , , (, Djb ChaCha SIMD?).

/* public domain, 2013 */

#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>

#define R(a,b) (((a) << (b)) | ((a) >> (32 - (b))))
static void salsa_scrambler(uint32_t out[16], uint32_t x[16])
{
    int i;
    /* This is a quickly mutilated Salsa20 of only 1 round */
    x[ 4] ^= R(x[ 0] + x[12],  7);
    x[ 8] ^= R(x[ 4] + x[ 0],  9);
    x[12] ^= R(x[ 8] + x[ 4], 13);
    x[ 0] ^= R(x[12] + x[ 8], 18);
    x[ 9] ^= R(x[ 5] + x[ 1],  7);
    x[13] ^= R(x[ 9] + x[ 5],  9);
    x[ 1] ^= R(x[13] + x[ 9], 13);
    x[ 5] ^= R(x[ 1] + x[13], 18);
    x[14] ^= R(x[10] + x[ 6],  7);
    x[ 2] ^= R(x[14] + x[10],  9);
    x[ 6] ^= R(x[ 2] + x[14], 13);
    x[10] ^= R(x[ 6] + x[ 2], 18);
    x[ 3] ^= R(x[15] + x[11],  7);
    x[ 7] ^= R(x[ 3] + x[15],  9);
    x[11] ^= R(x[ 7] + x[ 3], 13);
    x[15] ^= R(x[11] + x[ 7], 18);
    for (i = 0; i < 16; ++i)
        out[i] = x[i];
}

#define CHUNK 2048

int main(void)
{
    uint32_t bufA[CHUNK];
    uint32_t bufB[CHUNK];
    uint32_t *input = bufA, *output = bufB;
    int i;

    /* Initialize seed */
    srand(time(NULL));
    for (i = 0; i < CHUNK; i++)
        input[i] = rand();

    while (1) {
        for (i = 0; i < CHUNK/16; i++) {
            salsa_scrambler(output + 16*i, input + 16*i);
        }
        write(1, output, sizeof(bufA));

        {
            uint32_t *tmp = output;
            output = input;
            input = tmp;
        }
    }
    return 0;
}

Answer 6

I just created a (very simple and not optimized) C # console application that creates uncompressed files. It scans the folder for text files (extension .txt) and creates a binary file (extension .bin) with the same name and size for each text file. Hope this helps someone. Here is the C # code:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var files = Directory.EnumerateFiles(@"d:\MyPath\To\TextFile\", "*.txt");
            var random = new Random();
            foreach (var fileName in files)
            {
                var fileInfo = new FileInfo(fileName);
                var newFileName = Path.GetDirectoryName(fileName) + @"\" + Path.GetFileNameWithoutExtension(fileName) + ".bin";
                using (var f = File.Create(newFileName))
                {
                    long bytesWritten = 0;
                    while (bytesWritten < fileInfo.Length)
                    {
                        f.WriteByte((byte)random.Next());
                        bytesWritten++;
                    }
                    f.Close();
                }
            }
        }
    }
}

Answer 7

A very simple solution is to create a random string and then compress it. An already compressed file is incompressible.