Sortix 1.1dev nightly manual
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EVP_BYTESTOKEY(3) | Library Functions Manual | EVP_BYTESTOKEY(3) |
NAME
EVP_BytesToKey
—
password based encryption routine
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);
DESCRIPTION
EVP_BytesToKey
() derives a key and IV from
various parameters. type is the cipher to
derive the key and IV for. md is the message
digest to use. The 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.
data is a buffer containing
datal bytes which is used to derive the
keying data. count is the iteration count to
use. The derived key and IV will be written to
key and iv,
respectively.
A typical application of this function is to derive keying material for an
encryption algorithm from a password in the
data parameter.
Increasing the 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 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 more standard algorithms such as PBKDF2 as defined
in PKCS#5v2.1 for key derivation.
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 recursively as:D_i = HASH^count(D_(i-1) || data ||
salt)
RETURN VALUES
If data isNULL
,
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.
SEE ALSO
evp(3), EVP_EncryptInit(3), PKCS5_PBKDF2_HMAC(3)HISTORY
EVP_BytesToKey
() first appeared in SSLeay
0.5.1 and has been available since OpenBSD 2.4.June 7, 2019 | Debian |