Hi all, First of all, sorry for hash_hkdf() parameter discussion mess. I tried to described the issue clearly in the RFC. Although I've tried not to be repetitive, there are in order to avoid unnecessary confusions.
hash_hkdf() is simple hash_hmac() extension that allows to add non secret information(key context) to derive key(hash) from existing key. While hash_hkdf() is great function to implement various security features for web apps, it has inadequate/insecure parameter order/requirement and return value currently. This RFC proposes function signature improvement and value returned from the function, so that it has logical/consistent parameter order and return value. https://wiki.php.net/rfc/improve_hash_hkdf_parameter It includes some useful example HKDF applications with PHP. Since CSRF becomes one of the most serious threat in web app, "Advanced CSRF token" example might be one of the most used HKDF application with PHP. You may want to have a look the example at least even if you are not interested in hash functions. I don't see this kind of advanced CSRF token often. https://wiki.php.net/rfc/improve_hash_hkdf_parameter# example_4advanced_csrf_token Please make sure to distinguish "HKDF implementation requirement for specific application(usage)" and "General purpose HKDF function design and best practice". I presume this was the cause of previous discussion mess. (And my prejudice that fundamentals won't be mistaken) If you find any wrong or unclear statement, please let me know. I'll fix them gladly. I appreciate any improvement suggestions. If you would like send mail privately, I don't mind at all. Thank you for reading long RFC. TL;DR; https://wiki.php.net/rfc/improve_hash_hkdf_parameter#current_status Regards, -- Yasuo Ohgaki yohg...@ohgaki.net
