VeraCrypt

Documentation >> Security Requirements and Precautions >> Choosing Passwords and Keyfiles

Choosing Passwords and Keyfiles

It is very important that you choose a good password. You must avoid choosing one that contains only a single word that can be found in a dictionary (or a combination of such words). It must not contain any names, dates of birth, account numbers, or any other items that could be easy to guess. A good password is a random combination of upper and lower case letters, numbers, and special characters, such as @ ^ = $ * + etc. We strongly recommend choosing a password consisting of more than 20 characters (the longer, the better). Short passwords are easy to crack using brute-force techniques.

To make brute-force attacks on a keyfile infeasible, the size of the keyfile must be at least 30 bytes. If a volume uses multiple keyfiles, then at least one of the keyfiles must be 30 bytes in size or larger. Note that the 30-byte limit assumes a large amount of entropy in the keyfile. If the first 1024 kilobytes of a file contain only a small amount of entropy, it must not be used as a keyfile (regardless of the file size). If you are not sure what entropy means, we recommend that you let VeraCrypt generate a file with random content and that you use it as a keyfile (select Tools -> Keyfile Generator).

When creating a volume, encrypting a system partition/drive, or changing passwords/keyfiles, you must not allow any third party to choose or modify the password/keyfile(s) before/while the volume is created or the password/keyfiles(s) changed. For example, you must not use any password generators (whether website applications or locally run programs) where you are not sure that they are high-quality and uncontrolled by an attacker, and keyfiles must not be files that you download from the internet or that are accessible to other users of the computer (whether they are administrators or not).

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/*
  zip_fopen_index_encrypted.c -- open file for reading by index w/ password
  Copyright (C) 1999-2018 Dieter Baron and Thomas Klausner

  This file is part of libzip, a library to manipulate ZIP archives.
  The authors can be contacted at <libzip@nih.at>

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:
  1. Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
  2. Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.
  3. The names of the authors may not be used to endorse or promote
     products derived from this software without specific prior
     written permission.

  THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/


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

#include "zipint.h"

static zip_file_t *_zip_file_new(zip_t *za);


ZIP_EXTERN zip_file_t *
zip_fopen_index_encrypted(zip_t *za, zip_uint64_t index, zip_flags_t flags, const char *password) {
    zip_file_t *zf;
    zip_source_t *src;

    if ((src = _zip_source_zip_new(za, za, index, flags, 0, 0, password)) == NULL)
	return NULL;

    if (zip_source_open(src) < 0) {
	_zip_error_set_from_source(&za->error, src);
	zip_source_free(src);
	return NULL;
    }

    if ((zf = _zip_file_new(za)) == NULL) {
	zip_source_free(src);
	return NULL;
    }

    zf->src = src;

    return zf;
}


static zip_file_t *
_zip_file_new(zip_t *za) {
    zip_file_t *zf;

    if ((zf = (zip_file_t *)malloc(sizeof(struct zip_file))) == NULL) {
	zip_error_set(&za->error, ZIP_ER_MEMORY, 0);
	return NULL;
    }

    zf->za = za;
    zip_error_init(&zf->error);
    zf->eof = 0;
    zf->src = NULL;

    return zf;
}