Overwriting with random data (was: Re: /dev/tcp)

On 2026-08-24, Carlos E.R. wrote:

> On 2026-08-24 00:28, vallor wrote:
>> At Sun, 23 Aug 2026 13:50:30 +0200, "Carlos E.R." <[email protected]> wrote:
>
[snipping a lot to keep this shorter, apologies if I ended up snipping
too much]
>
>>> I wrote a program that writes bytes on big partitions.
>>>
>>>
>>> excerpted:
>>>
>>> const
>>>        sourcefilename = './BigRandom';
>>>        rawdest: string = '';     // example: '/dev/sda11'
>>>
>>>        shuflecount = 1024;
>>>        arraysize = 1023;
>>>        ChunkSz=1048576;
>>> type
>>>        tCacho= array [1..ChunkSz] of byte;
>>>
>>> var
>>>      Fin, Fout: file of tCacho;
>>>      gotresult: Word;
>>>
>>>      BigData : array [1..shuflecount] of tCacho;
>>>      OutputIndex : Int64;	// counts MiB written.
>>>
>>>
>>> begin
>>>
>>> // writes one MiB
>>>         {$I-}write(Fout,BigData[RandomIndex]);{$I+}
>>>         gotresult:= ioresult;
>>>
>>>
>>>
>>> The purpose of the program is to fast fill a partition or disk with
>>> nearly true random data. It is as fast as dd could be.
>>
>> SHRED(1)                 User Commands                 SHRED(1)
>>
>> NAME
>>         shred  -  overwrite  a  file  to  hide its contents, and
>>         optionally delete it
>>
>> SYNOPSIS
>>         shred [OPTION]... FILE...
>>
>> DESCRIPTION
>>         Overwrite the specified FILE(s) repeatedly, in order  to
>>         make  it harder for even very expensive hardware probing
>>         to recover the data.
>
> Not the same thing.

IIRC shred can do the same, and on block devices too, what's the
difference here? block sizes?

-- 
Nuno Silva