[messaging] PBKDF2 vs bcrypt vs scrypt ... when dealing with browsers

Tao Effect contact at taoeffect.com
Fri Dec 19 21:52:51 PST 2014

Question for the crypto-gurus out there (skip to TLDR if you want).

What is the best practice (for today) when dealing with passwords over websites, given the following context and assumptions:


- Hashed/encrypted passwords stored in server database
- User enters password in form and sends to server over HTTPS
- KDF algorithm shouldn't run for more than 2 seconds on any modern mobile device


- It is better to send the encrypted password over the wire than the password itself

Known knowns:

- Server can run all three KDFs natively.
- Clients (web browsers) can only run PBKDF2 natively for browsers that support that part of the WebCrypto spec


That last part is the crux of the question: since only PBKDF2 (might) be supported natively, and scrypt/bcrypt are forced to run in JS, does that imply that in the case of login forms PBKDF2 is actually /more secure/ than scrypt/bcrypt given our 2 second runtime constraint?

How do I even begin to test/validate this question?

Many thanks!

Greg Slepak

Please do not email me anything that you are not comfortable also sharing with the NSA.

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