PKCS5_PBKDF2_HMAC documentation submitted by Jeffrey Walton

doc/crypto/EVP_BytesToKey.pod

@@ -60,6 +60,7 @@ 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

doc/crypto/PKCS5_PBKDF2_HMAC.pod

+=pod
+
+=head1 NAME
+
+PKCS5_PBKDF2_HMAC - password based derivation routine with salt and iteration count
+
+=head1 SYNOPSIS
+
+ #include <openssl/evp.h>
+
+ int PKCS5_PBKDF2_HMAC(const char *pass, int passlen,
+                       const unsigned char *salt, int saltlen, int iter,
+                       const EVP_MD *digest,
+                       int keylen, unsigned char *out);
+
+=head1 DESCRIPTION
+
+PKCS5_PBKDF2_HMAC() derives a key from a password using a salt and iteration count
+as specified in RFC 2898.
+
+B<pass> is the password used in the derivation of length B<passlen>. B<pass>
+is an optional parameter and can be NULL. If B<passlen> is -1, then the
+function will calculate the length of B<pass> using strlen().
+
+B<salt> is the salt used in the derivation of length B<saltlen>. If the
+B<salt> is NULL, then B<saltlen> must be 0. The function will not
+attempt to calculate the length of the B<salt> because its not assumed to
+be NULL terminated.
+
+B<iter> is the iteration count and its value should be greater than or 
+equal to 1. RFC 2898 suggests an iteration count of at least 1000. Any
+B<iter> less than 1 is treated as a single iteration.
+
+B<digest> is message digest function used in the derivation. Values include
+any of the EVP_* message digests. PKCS5_PBKDF2_HMAC_SHA1() calls
+PKCS5_PBKDF2_HMAC() with EVP_sha1().
+
+The derived key will be written to B<out>. The size of the B<out> buffer
+is specified via B<keylen>.
+
+=head1 NOTES
+
+A typical application of this function is to derive keying material for an
+encryption algorithm from a password in the B<pass>, a salt in B<salt>,
+and an iteration count.
+
+Increasing the B<iter> 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.
+
+=head1 RETURN VALUES
+
+PKCS5_PBKDF2_HMAC() returns 1 on success or 0 on error.
+
+=head1 SEE ALSO
+
+L<evp(3)|evp(3)>, L<rand(3)|rand(3)>,
+L<EVP_BytesToKey(3)|EVP_BytesToKey(3)>
+
+=head1 HISTORY
+
+=cut