LibGCrypt Examples

[kingruedi]

> You can disable it with:
>
>         gcry_control( GCRYCTL_DISABLE_SECMEM_WARN )
>
> or you can set your program set uid. It's the same with the
> GNU Privacy Guard, to use the secure memory you need root privileges.

now it works! But the output doesn't look like a md5 checksum :(

here is my source

#include <gcrypt.h>
#include <stdio.h>

int main(int argc,char **argv)
{
  GCRY_MD_HD md5;
  FILE *fd;
  unsigned char buffer[500];
  size_t len;
  int a;

  if(argc<2)
  {
    fprintf(stderr,"usage: %s <file>\n",*argv);
    return 1;
  }
  if( (fd=fopen(*(argv+1),"r")) ==NULL)
  {
    perror("Couldn't open file!\n");
    return 1;
  }

  gcry_control( GCRYCTL_DISABLE_SECMEM_WARN );
  gcry_control( GCRYCTL_INIT_SECMEM, 16384, 0 );
  md5=gcry_md_open(GCRY_MD_MD5,GCRY_MD_FLAG_HMAC);
  if( (len=fread(buffer,sizeof(unsigned char),500,fd)) ==0)
  {
    if(ferror(fd))
    {
      perror("Couldn't read file!\n");
      return 1;
    }
  }
  gcry_md_write(md5,buffer,len); /*<-- this should create the checksum*/
  printf("%s\n",buffer);
  gcry_md_close(md5);
  return 0;
}

sorry that I ask this simple questions but I didn't understood the reference