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> paramter is used as a salt in the derivation: it should point to
+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>
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 peform a brute force attack using a large number
+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 more standard algorithms such as PKCS#5
-v2.0 for key derivation.
+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
D_i = HASH^count(D_(i-1) || data || salt)
-where || denotes concatentaion, D_0 is empty, HASH is the digest
+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.
=head1 RETURN VALUES
-EVP_BytesToKey() returns the size of the derived key in bytes, or 0 on error.
+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(3)|evp(3)>, L<rand(3)|rand(3)>,
+L<PKCS5_PBKDF2_HMAC(3)|PKCS5_PBKDF2_HMAC(3)>,
L<EVP_EncryptInit(3)|EVP_EncryptInit(3)>
=head1 HISTORY