#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);
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 a more modern algorithm such as PBKDF2 as defined in PKCS#5v2.1 and provided by PKCS5_PBKDF2_HMAC.
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.
Licensed under the OpenSSL license (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 https://www.openssl.org/source/license.html.