# [VOTE] Hash_pbkdf2 - Thread: https://externals.io/message/61065 - Original archive: https://news-web.php.net/php.internals/61065 - Started by Anthony Ferrara on 2012-07-02T16:34:30+00:00 - Messages: 7 - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #61065 — Anthony Ferrara — 2012-07-02T16:34:30+00:00 URL: https://externals.io/message/61065#61065 Hello all, I've opened voting for the hash_pbkdf2 RFC adding `hash_pbkdf2()` to master: https://wiki.php.net/rfc/hash_pbkdf2#vote Thanks, Anthony --- ## #61066 — Paul Dragoonis — 2012-07-02T16:38:11+00:00 URL: https://externals.io/message/61065#61066 · In reply to: #61065 I see no coding examples, just a function declaration. > Hello all, > > I've opened voting for the hash_pbkdf2 RFC adding `hash_pbkdf2()` to master: > > https://wiki.php.net/rfc/hash_pbkdf2#vote > > Thanks, > > Anthony --- ## #61067 — Anthony Ferrara — 2012-07-02T16:50:00+00:00 URL: https://externals.io/message/61065#61067 · In reply to: #61066 Paul > I see no coding examples, just a function declaration. I've updated the RFC adding 2 examples. Anthony --- ## #61074 — Sara Golemon — 2012-07-03T00:24:53+00:00 URL: https://externals.io/message/61065#61074 · In reply to: #61065 I'd like to see `hash_init()` support this mode as well (for completeness). Perhaps something like the following: $ctx = hash_init("sha512", HASH_PBKDF2, $salt, array('length' => 32, 'iterations' => 5000)); The new fourth parameter being an overloadable options generic so that we don't have an endless list of parameters for all the possible hashing types. -Sara > Hello all, > > I've opened voting for the hash_pbkdf2 RFC adding `hash_pbkdf2()` to master: > > https://wiki.php.net/rfc/hash_pbkdf2#vote > > Thanks, > > Anthony --- ## #61075 — Anthony Ferrara — 2012-07-03T00:49:03+00:00 URL: https://externals.io/message/61065#61075 · In reply to: #61074 Sara, > I'd like to see `hash_init()` support this mode as well (for completeness). >  Perhaps something like the following: > > $ctx = hash_init("sha512", HASH_PBKDF2, $salt, array('length' => 32, > 'iterations' => 5000)); > > The new fourth parameter being an overloadable options generic so that we > don't have an endless list of parameters for all the possible hashing types. The only problem that I have with this sort of implementation is that the only way it would work is to buffer the entire input (each hash_update call), and run it all at the end. That's because the data (password) is used in every iteration, so there's no pre-computation that can be done. And at that point, what's the benefit to it? public function pbkdf2($algo, $password, $salt, $iterations, $length) { $size = getHashBlockSize($hash); $len = ceil($length / $size); $result = ''; for ($i = 1; $i <= $len; $i++) { $tmp = hash_hmac($hash, $salt . pack('N', $i), $password, true); $res = $tmp; for ($j = 1; $j < $iterations; $j++) { $tmp = hash_hmac($hash, $tmp, $password, true); $res ^= $tmp; } $result .= $res; } return substr($result, 0, $length); } Contrast that to a normal hash function (used by the current hash_init) which iterates over blocks of input, and once it's done with a block, it doesn't need it anymore (which is where using something like hash_init/hash_update can make sense on large input). Additionally, hmac only uses the message in a single hash, so it can be streamed in as well (pre-compute the earlier hashes/data, stream the intermediate hash, then hash the final one). So while it could be added (just make hash_update buffer into a context, then have hash_final actually run the derivation), I'm not sure it makes sense to add it there. Thoughts? Anthony --- ## #61076 — Sara Golemon — 2012-07-03T02:37:10+00:00 URL: https://externals.io/message/61065#61076 · In reply to: #61075 > Sara, > > > > […] > types. > > The only problem that I have with this sort of implementation is that > the only way it would work is to buffer the entire input (each > hash_update call), and run it all at the end. That's because the data > (password) is used in every iteration, so there's no pre-computation > that can be done. And at that point, what's the benefit to it? > > public function pbkdf2($algo, $password, $salt, $iterations, $length) { > $size = getHashBlockSize($hash); > $len = ceil($length / $size); > $result = ''; > for ($i = 1; $i <= $len; $i++) { > $tmp = hash_hmac($hash, $salt . pack('N', $i), $password, > true); > $res = $tmp; > for ($j = 1; $j < $iterations; $j++) { > $tmp = hash_hmac($hash, $tmp, $password, true); > $res ^= $tmp; > } > $result .= $res; > } > return substr($result, 0, $length); > } > > Contrast that to a normal hash function (used by the current > hash_init) which iterates over blocks of input, and once it's done > with a block, it doesn't need it anymore (which is where using > something like hash_init/hash_update can make sense on large input). > > Additionally, hmac only uses the message in a single hash, so it can > be streamed in as well (pre-compute the earlier hashes/data, stream > the intermediate hash, then hash the final one). > > So while it could be added (just make hash_update buffer into a > context, then have hash_final actually run the derivation), I'm not > sure it makes sense to add it there. > > Thoughts? > > Anthony > Ah, wasn't clear on how pbkdf2 worked. Your argument makes total sense. Thanks for explaining it. :) --- ## #61119 — Anthony Ferrara — 2012-07-10T14:14:16+00:00 URL: https://externals.io/message/61065#61119 · In reply to: #61076 Hey all, The voting phase has ended for hash_pbkdf2, and it has passed with a vote of 8:0. I've moved the RFC into Accepted state, and will merge the PR today into master, then move the RFC into Implemented. Thanks! Anthony > > > On Mon, Jul 2, 2012 at 5:49 PM, Anthony Ferrara wrote: > > > […] > > Ah, wasn't clear on how pbkdf2 worked. Your argument makes total sense. > Thanks for explaining it. :)