Password based key derivation

[noloader@xxxxxxxxx (Jeffrey Walton)]

>  1)      Can the function PKCS5_PBKDF2_HMAC_SHA1() in 0.9.8zf be used to
> derive a key for AES-256-CBC encryption from user supplied passphrase?

For the function PKCS5_PBKDF2_HMAC_SHA1, Yes. See
https://wiki.openssl.org/index.php/Manual:PKCS5_PBKDF2_HMAC(3).

I'm not sure what the significance of 0.9.8zf is.

> 2)     Is PKCS5_PBKDF2_HMAC_SHA1() preferable to EVP_BytesToKey()  and why ?

Yes. See https://wiki.openssl.org/index.php/Manual:EVP_BytesToKey(3).