Re: [News] MD5 / SHA-1 Encryptions Weakened

"Mark Randall" <mark[__OKTHISISFAKE_]yr@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote in message news:uA7e99r5FHA.3588@xxxxxxxxxxxxxxxxxxxx
> Bad news for application developers (hence this post).
>
> After several months of processing, MD5 and SHA1 lookup tables have
> been generated upto 14 characters in length. See
> http://www.theregister.co.uk/2005/11/10/password_hashes/
>
> The related site:
> http://www.rainbowcrack-online.com/?x=pricing

Note that this technique is very easily thwarted by salting your hashes.
Most modern systems dealing with passwords salt them already, and those
that don't should run, not walk, and implement salting.

Salting is a very simple technique. You generate a random number (called
salt value or simply salt), append it to the password and hash them
together. You then store the hash together with the salt. To verify the
password, you append the stored salt value to it, hash them, and compare
with the hash you calculated when the password was created.

The reason it works against rainbow table attack is that now the
attacker has to precompute hashes for every combination of password and
salt, not just for every password. With large enough salt values (64-bit
is typical) the task becomes infeasible. This can be further aided by
applying stretching, which effectively makes passwords longer.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925


.

Relevant Pages

  • Re: How good an encryption algorithm is this?
    ... Actually it's vitally important that the salt is different every time. ... but a one-way hash of the password). ... >>> attack (using my dictionary of plaintext trial passwords and the ... you need to perform this iteration only once. ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: How good an encryption algorithm is this?
    ... Actually it's vitally important that the salt is different every time. ... but a one-way hash of the password). ... >>> attack (using my dictionary of plaintext trial passwords and the ... you need to perform this iteration only once. ...
    (microsoft.public.vc.language)
  • Hash salting -- digression
    ... Something that goes hand-in-hand with a salt is an iteration count. ... If an IC causes the hash ... is exactly to make using a dictionary attack computationally unfeasible. ... As far as crypto is concerned, its hard to explain that the strength of any ...
    (SecProg)
  • Re: Is this secure
    ... What I do in my business layer I get the salt, then I use my custom classes ... to hash the passed in password then send the Hash to a Stored Proc to ... Both the hashed password and salt are stored in the database. ... but then i'd need the salt to create a saltedhash to ...
    (microsoft.public.dotnet.framework.aspnet)
  • Re: Can Kerberos be cracked??
    ... Subject: Can Kerberos be cracked?? ... A "salt" is a "random" value that is appended to the ... possible for you to dictionary-crack my password unless you know the ... >> In order to get the hash you would need to launch a brute force attack ...
    (Focus-Microsoft)