Passwords and security keys that were saved in prior versions of WordPress will continue to work. Each user's password will be opportunistically rehashed and resaved when they next subsequently log in using a valid password.
The following new functions have been introduced:
* `wp_password_needs_rehash()`
* `wp_fast_hash()`
* `wp_verify_fast_hash()`
The following new filters have been introduced:
* `password_needs_rehash`
* `wp_hash_password_algorithm`
* `wp_hash_password_options`
Props ayeshrajans, bgermann, dd32, deadduck169, desrosj, haozi, harrym, iandunn, jammycakes, joehoyle, johnbillion, mbijon, mojorob, mslavco, my1xt, nacin, otto42, paragoninitiativeenterprises, paulkevan, rmccue, ryanhellyer, scribu, swalkinshaw, synchro, th23, timothyblynjacobs, tomdxw, westi, xknown.
Additional thanks go to the Roots team, Soatok, Calvin Alkan, and Raphael Ahrens.
Fixes#21022, #44628
Built from https://develop.svn.wordpress.org/trunk@59828
git-svn-id: http://core.svn.wordpress.org/trunk@59170 1a063a9b-81f0-0310-95a4-ce76da25c4cd
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