How do I do "wipe" in WinNT

[Wesley J Landaker]

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On Monday 30 October 2000  8:05pm, Kevin Hung wrote:
> I am using GNUPG in WinNT at work (I know that this is
> not the favorite OS for GNU people but I don't have a
> choice) and I would like to have the "wipe" feature as
> availabe in PGP or the shred command in Linux. Is
> there any similar thing like shred in NT? Thanks.

If there's not already something that does that in Windows from the 
command line (I know some gui utilities that do it, and of course PGP 
does--but this assuming you're not using PGP), this should do the trick 
(this does exactly what most utilities like shred do--overwrite with 
'1's, '0's, and random bytes. Of course, you need a better random 
source than "rand()" usually, but this should probably be okay 
anyway--heck, we're using 50 iterations!!!)

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void do_shredding(const char file[]);

int main(int argc, char *argv[]) {

  if (argc < 2) {
    printf("Cheapskate-shred -- this will shred files as good as 
anything else...\n");
    printf("Usage: %s <file> ...\n",argv[0]);
    return 1;
  }

  for (int i=1;i<argc;i++) {
    do_shredding(argv[i]);
  }

  return 0;

}

void do_shredding(const char file[]) {
  const char ones = 0xff;
  const char zeros = 0x00;
  char random;
  
  FILE *shred_me = fopen(file,"r+b");

  fseek(shred_me,0,SEEK_END);

  int file_len = ftell(shred_me);

  time_t t;
  srand(time(&t));

  // do this for 50 iterations -- plenty, probably
  for (int iter=0;iter<50;iter++) {
    // first write 1's
    rewind(shred_me);
    for (int i=0;i<file_len;i++) {
      fwrite(&ones,1,1,shred_me);
    }
    // then write 0's
    rewind(shred_me);
    for (int i=0;i<file_len;i++) {
      fwrite(&zeros,1,1,shred_me);
    }
    // then (probably pseudo-) random bytes 
    rewind(shred_me);
    for (int i=0;i<file_len;i++) {
      random = rand();
      fwrite(&random,1,1,shred_me);
    }
  }
  
}


- -- 
Wesley J. Landaker - wjl@mindless.com           ICQ# 17241646
http://wjl.cjb.net                 PGP DSS/DH Key: 0x0F338E07
PGPKey FP: 3AAA 424B B488 198E B68B  C0E5 390A BACA 0F33 8E07
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