Hacker News Reader

Comment by JimmaDaRustla | Hacker News Reader

Excuse my ignorance, but you probably shouldn't be able to reverse an irreversible hash.

The point of hashing passwords is that the true password is not revealable.

The point of salting password hashes is to prevent identical cleartext passwords from being stored as identical hashes in the database. Salts are often stored in the database, as well.

The point of peppering keeps a database dump from being at all useful for recovering passwords. It make sure that a component of the process of cleartext -> DB entry is not even in the database, requiring something from the app as well.

Why does encryption work here? Because you've already done a one way function on the cleartext -> salted hash. At that point, there is still no way to reverse the process all the way to get the cleartext. By using a two-way encryption function for the pepper portion, you keep the ability to rotate 'peppers' periodically, in case it is leaked, for example.

Thanks for the informative post

The pepper is being used as an encryption key in that example rather than using hashing.

In pacofvf's example, you are correct.

But, the original example is hashing the password. No encryption involved. So what makes anyone think that they can reverse a hash?

The problem is that pacofvf's answer assumes you don't need to do this retroactively.

This would work if you were building a new system today, but if you had a DB full of one way hashes you're not going to be able to retroactively modify the pepper.

And more importantly, slack straight up stated they salt the password and use bcrypt. It's all one way hashes, no encrypting/decrypting going on.

It's reversing the encryption, not the hash.

Where in the original example was encryption involved? The salt and pepper were only ever used in a hashing algorithm.

The pepper is the key to the encryption, not a hashing algorithm.

Thanks for just ignoring my question - THERE IS NO ENCRYPTION IN THE ORIGINAL ARTICLE, so WHY are you restating that encryption is involved at all?

Straight from the original artical:

  hashed_password = scrypt(password, salt + pepper)

  hashed_password = scrypt(scrypt(password, salt),pepper)

Absolutely zero encryption going on here. Therefore, no ability to "decrypt" the pepper result. The pepper IS NOT a key for encryption. Period.

Reply on news.ycombinator.com