Hacker News Reader

Comment by cylon13 | Hacker News Reader

Hashing is done on the server. Hashing on the client would defeat the whole purpose.

Why? If you hash on the server, then you have to send the password in plaintext to the server.

EDIT: Oh right, salts.

More importantly if the server just accepts hashed passwords and stores them, then if you got ahold of a hashed password through a leak you could just use it directly to authenticate by modifying the client. The hashed password just becomes the password with one extra client-side step that you can trivially skip.

Salting is more about making it non-obvious which passwords map to which hashes so you can’t easily build tables of hashes for common passwords.

Sending the password to the server in “plain text” is fine over https, it’s a secure channel. Hashing isn’t meant to hide the password on the wire, it’s to prevent anyone with access to the database from learning what the passwords are.

Great point, thanks!

If you do not want to send them in plain text you can use SCRAM.

The server could hash again the hashed password sent by the client. Especially if the client use an insecure hash algorithm (no secret salt for example).

I feel like if the client always hash passwords as soon as it is typed (the javascript never sees the unhashed password), no one would notice. (except some with crazy password rules that would disallow a hash-looking password)

There are formalized approaches to keeping the server from knowing the password at any time: https://en.m.wikipedia.org/wiki/Password-authenticated_key_a...

SRP is one such system: https://en.m.wikipedia.org/wiki/Secure_Remote_Password_proto...

The various ZKP approaches are considerably more complex to implement properly vs the trivial approach of a client side hash. There are obvious tradeoffs, of course, but I wouldn't fault someone for an additional hash step on the client.

Hashing on the client still seems redundant though. In the end, whatever value is sent to the server is essentially plaintext, because it's all an attacker needs to know to authenticate. Whether it's the raw text the user typed or some transformed version of it isn't really relevant.

In a world where password reuse is rampant, whether it's the raw text the user typed or a hard-to-reverse transformation on it is absolutely relevant to the user, just not to the service provider.

Reply on news.ycombinator.com