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QoTW #45: Is my developer’s home-brew password security right or wrong, and why?

2013-04-05 by . 0 comments

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An incredibly popular question, viewed 17000 times in its first 3 weeks, this question has even led to a new Sec.SE meta meme.

In fact, our top meta meme explains why – the First Rule of Crypto is “Don’t Roll Your Own!”

So, with that in mind, Polynomial’s answer, delivered with a liberal dose of snark, explains in simple language:

This home-brew method offers no real resistance against brute force attacks, and gives a false impression of “complicated” security…Stick to tried and tested key derivation algorithms like PBKDF2 or bcrypt, which have undergone years of in-depth analysis and scrutiny from a wide range of professional and hobbyist cryptographers.

Konerak lists out some advantages of going with an existing public protocol:

  • Probably written by smarter people than you
  • Tested by a lot more people (probably some of them smarter than you)
  • Reviewed by a lot more people (probably some of them smarter than you), often has mathematical proof
  • Improved by a lot more people (probably some of them smarter than you)
  • At the moment just one of those thousands of people finds a flaw, a lot of people start fixing it

KeithS also gives more detail:

  • MD5 is completely broken
  • SHA-1 is considered vulnerable
  • More hashes don’t necessarily mean better hashing
  • Passwords are inherently low-entropy
  • This scheme is not adding any significant proof of work

Along with further answers, the discussion on this post covered a wide range of issues – well worth reading the whole thing!

Liked this question of the week? Interested in reading it or adding an answer? See the question in full. Have questions of a security nature of your own? Security expert and want to help others? Come and join us at security.stackexchange.com.

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