Automatically generated by Pod::Man 4.07 (Pod::Simple 3.32)
(The comments found at the beginning of the groff file "man3/EVP_BytesToKey.3ssl".)
EVP_BytesToKey - password based encryption routine
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);
derives a key and
from various parameters. type
the cipher to derive the key and
is the message digest to use.
parameter is used as a salt in the derivation: it should point to
an 8 byte buffer or
if no salt is used. data
is a buffer containing
bytes which is used to derive the keying data. count
iteration count to use. The derived key and
will be written to key
A typical application of this function is to derive keying material for an
encryption algorithm from a password in the data
Increasing the count parameter slows down the algorithm which makes it
harder for an attacker to peform a brute force attack using a large number
of candidate passwords.
If the total key and
length is less than the digest length and
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
defined in PKCS#5v2.1 and provided by
KEY DERIVATION ALGORITHM
The key and
is derived by concatenating D_1, D_2, etc until
enough data is available for the key and
D_i is defined as:
D_i = HASH^count(D_(i-1) || data || salt)
where || denotes concatentaion, D_0 is empty,
is the digest
algorithm in use, HASH^1(data) is simply
(data)) and so on.
The initial bytes are used for the key and the subsequent bytes for
returns the number of bytes
needed to store the derived key.
returns the size of the derived key in bytes,
or 0 on error.