mirror of
https://github.com/CloverHackyColor/CloverBootloader.git
synced 2024-12-02 13:03:28 +01:00
79 lines
2.6 KiB
Plaintext
79 lines
2.6 KiB
Plaintext
=pod
|
|
|
|
=head1 NAME
|
|
|
|
EVP_BytesToKey - password based encryption routine
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/evp.h>
|
|
|
|
int EVP_BytesToKey(const EVP_CIPHER *type, const EVP_MD *md,
|
|
const unsigned char *salt,
|
|
const unsigned char *data, int datal, int count,
|
|
unsigned char *key, unsigned char *iv);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
EVP_BytesToKey() derives a key and IV from various parameters. B<type> is
|
|
the cipher to derive the key and IV for. B<md> is the message digest to use.
|
|
The B<salt> parameter is used as a salt in the derivation: it should point to
|
|
an 8 byte buffer or NULL if no salt is used. B<data> is a buffer containing
|
|
B<datal> bytes which is used to derive the keying data. B<count> is the
|
|
iteration count to use. The derived key and IV will be written to B<key>
|
|
and B<iv> respectively.
|
|
|
|
=head1 NOTES
|
|
|
|
A typical application of this function is to derive keying material for an
|
|
encryption algorithm from a password in the B<data> parameter.
|
|
|
|
Increasing the B<count> parameter slows down the algorithm which makes it
|
|
harder for an attacker to perform a brute force attack using a large number
|
|
of candidate passwords.
|
|
|
|
If the total key and IV length is less than the digest length and
|
|
B<MD5> is used then the derivation algorithm is compatible with PKCS#5 v1.5
|
|
otherwise a non standard extension is used to derive the extra data.
|
|
|
|
Newer applications should use a more modern algorithm such as PBKDF2 as
|
|
defined in PKCS#5v2.1 and provided by PKCS5_PBKDF2_HMAC.
|
|
|
|
=head1 KEY DERIVATION ALGORITHM
|
|
|
|
The key and IV is derived by concatenating D_1, D_2, etc until
|
|
enough data is available for the key and IV. D_i is defined as:
|
|
|
|
D_i = HASH^count(D_(i-1) || data || salt)
|
|
|
|
where || denotes concatenation, D_0 is empty, HASH is the digest
|
|
algorithm in use, HASH^1(data) is simply HASH(data), HASH^2(data)
|
|
is HASH(HASH(data)) and so on.
|
|
|
|
The initial bytes are used for the key and the subsequent bytes for
|
|
the IV.
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
If B<data> is NULL, then EVP_BytesToKey() returns the number of bytes
|
|
needed to store the derived key.
|
|
Otherwise, EVP_BytesToKey() returns the size of the derived key in bytes,
|
|
or 0 on error.
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<evp(7)>, L<RAND_bytes(3)>,
|
|
L<PKCS5_PBKDF2_HMAC(3)>,
|
|
L<EVP_EncryptInit(3)>
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved.
|
|
|
|
Licensed under the Apache License 2.0 (the "License"). You may not use
|
|
this file except in compliance with the License. You can obtain a copy
|
|
in the file LICENSE in the source distribution or at
|
|
L<https://www.openssl.org/source/license.html>.
|
|
|
|
=cut
|