david wong

Hey! I'm David, a security engineer at the Blockchain team of Facebook, previously a security consultant for the Cryptography Services of NCC Group. I'm also the author of the Real World Cryptography book. This is my blog about cryptography and security and other related topics that I find interesting.

How to store passwords? Hash or KDF? posted April 2014

I remember a time where people would advise to just hash the password with md5 before storing it into a database.

Then md5 became a bad choice because of the rainbow tables (precomputed tables of md5). The concept of salt helped (adding a secret value to passwords before hashing them).

But hash were never meant for encrypting passwords. As KDF. But KDF seems to be better a fit for that kind of task.

See Ty's blog post "please stop hashing passwords". He makes good points and advise using those following KDFs for the job:

  • bcrypt
  • scrypt
  • pbkdf2

Scrypt is the one used in Litecoin by the way.


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