Re: reveal password fix needed

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: Dave (Nobody_at_Nowhere.Com)
Date: 12/07/04 

Date: Tue, 7 Dec 2004 11:09:14 -0000

> Is there any point in a hash at all?
> If they can't reverse the hash to produce the original password, they
> could
> reverse the hash to something which would produce that hash again.
> Couldn't
> they? Wouldn't that be good enough?

Er, how?

Reversing the hash to provide a equivilent initial code is (if the hash is
well designed) beyond the means of anybody not degree level trained in
cryptology, you could try brute force, but that would work against any
password. I disable the program for 5 minutes after 3 bad passwords which
would make brute force out of the question. (I also note the attempt in an
audit trail but that is a different story)

If you think the hash is too weak, then do 2 different hashes and either
join or interlace the two, then an interloper would have to find a reverse
which would work for both hashes simultaneously - probably not possible.

I do a simple hash based on the ascii values and the position of each
character, my way of making it hard to reverse is to throw away most of the
significant figures, I get a 10 digit number which I think would be hard to
crack.

If you are still worried about the mask, don't bother with it, actually show
blobs or asterisks and redirect keyboard entry to a string and do all the
hard stuff in code.

Dave.

Relevant Pages

  • Re: Regarding sudo
    ... if both passwords collide in the same hash. ... Here is an md5sum: 4d5fcfe735a39ff224d7cf2bac0d8aa7 Reverse it. ... and i can't find info if during the timestamp, sudo will allow to be used by ...
    (comp.os.linux.setup)
  • Re: Why unhashing is not possible?
    ... for example let's add the word 'Pie' to our hash table, ... The key 'Apple' hashes to 0x41, ... Since the database key is 24 bits, 72 bits, or even of variable length, ... The only way we have of constructing a function to 'reverse' the hash ...
    (comp.security.misc)
  • Inverting a hash safely
    ... The standard answer on how to invert a hash, so that keys become values and vice ... versa, is to use reverse: ... does there exist a 'safe hash invert' function in some CPAN ...
    (perl.beginners)
  • Re: Inverting a hash safely
    ... It's not so much a user error message as an assertion ... failure - the assumption made by the programmer, ... 'the hash is one-to-one') and then the assertions and other checks are firstly ... the pattern of 'check unique values; now reverse it' is common enough ...
    (perl.beginners)
  • Re: Why unhashing is not possible?
    ... be used within programs and fast database lookups but I failed ... understand when I told them that you cannot reverse the process... ... Many many many many inputs give the same hash. ... And at each step in the hash, information is thrown away. ...
    (comp.security.misc)