« previous next »
Pages: 1 2 3 4 5 [6] 7 8

Author Topic: What is the point of MD5?  (Read 32219 times)

0 Members and 2 Guests are viewing this topic.

Offline cs.punk

  • Enthusiast
  • Posts: 406
  • Gender: Male
  • Uhm er well...
    • View Profile
Re: What is the point of MD5?
« Reply #75 on: June 14, 2009, 04:15:18 PM »
Well, hmm interesting...

Though I wonder to myself... Theres a infinite number of numbers (literally)... How does MD5 account for this?

Theoretically speaking,
A MD5 hash is 32 characters long
So (number wise speaking)....

1-9999,9999,9999,9999,9999,9999,9999,9999
Should have no collision...

1-9,9999,9999,9999,9999,9999,9999,9999,9999
Should have 1 hash for 10 different numbers...

1-9999,9999,9999,9999,9999,9999,9999,9999,9999
Should have 1 hash for 1000 different numbers...

1-9999,9999,9999,9999,9999,9999,9999,9999,9999,9999
Should have 1 hash for 10 million different numbers...

And the cycle continues?...

I confused myself way to much to even understand all this lol... I bet I don't even make sense.
Logged
Life isn't just simply being alive... Or is it?

Offline Daniel0

  • Administrator
  • 'Insane!'
  • *
  • Posts: 11,815
  • Gender: Male
  • ^bb|[^b]{2}$
    • View Profile
Re: What is the point of MD5?
« Reply #76 on: June 14, 2009, 04:43:45 PM »
It solves that by having some inputs share the same hash.

Consider this function: f(x) = x mod 10. Here you have f(1) = f(11) = f(21), etc. (I had an example with that one earlier)

Also consider this: g(x) = x2 => g(x) = g(|x|) (e.g. g(1) = g(-1), but 1 != -1). These functions are surjections, that's to say they "fill out" their codomains.

Said in another way, a hashing function is a function of the form [tex]f : X \to Y[/tex] where [tex]|X| = \infty[/tex] and [tex]|Y| \in \mathbb{R}[/tex].
« Last Edit: June 14, 2009, 04:45:47 PM by Daniel0 »
Logged

Offline pkedpker

  • Enthusiast
  • Posts: 172
    • View Profile
Re: What is the point of MD5?
« Reply #77 on: June 14, 2009, 04:45:07 PM »
Yar 99% of sites that don't use mysql store passwords in txt files somewhere on the site.. and 80% of these portals that people install don't even care where passwords are stored can be easily used to access a person's credentials. Such as PBLang - International PHP-forum I've used it on a free host that doesn't support mySQL.. you can see a persons password in md5 using a simple URL

host.com/pbLang/db/members/userGoeshere

Now searching in google using this string
Software PBLang 4.67.16.a © 2002-2006 by Martin Senftleben & the PBLang-Team

you will find many forums hosted and in many you can access persons password which is encoded with md5..

what makes it secure? it just is.. thats all you gotta say
Logged
My main langauges I've learned since I've gotten into the computer world.. were Assembly and Basic together they made me into a god of hacking/cracking. A few years ago I learned C. Realized how much C helped me with picking up other langauges in a breeze like most importantly PHP =)

Offline jxrd

  • Enthusiast
  • Posts: 225
    • View Profile
Re: What is the point of MD5?
« Reply #78 on: June 14, 2009, 06:02:17 PM »
Damn right what's the point of MD5 when we've got this...
Logged

Offline MadTechie

  • Guru
  • Freak!
  • *
  • Posts: 9,374
  • Gender: Male
  • I try to F1
    • View Profile
Re: What is the point of MD5?
« Reply #79 on: June 14, 2009, 06:34:03 PM »
Quote from: pkedpker on June 14, 2009, 04:45:07 PM
what makes it secure? it just is.. thats all you gotta say
The fact you even ask that mean you haven't read the whole thread, so as I have said before, I don't repeat myself,
If you really want to know then read the whole thread this has been covered ready.

Simply put MD5 is a one-way hash function that expects a plaintext password and then outputs a hash, This hash is mathematically irreversible, meaning that it is impossible to determine the original password using only the hash.

Daniel0 and I have tried to explain this in this thread...
Logged
Computers are good at following instructions, but not at reading your mind.
Quote from: Maq on March 11, 2009, 01:10:25 PM
The quality of a response, is usually directly related to the quality of the question. ©2009 mjdamato
Quote from: Nightslyr on February 03, 2010, 06:35:48 PM
I dunno about that.  A regular expression has a 0% chance of touching my penis.
Quote from: redarrow on October 09, 2009, 06:56:35 AM
the code is professionally made up but not working
Remember to Click Solved, how to ask questions - the smart way

Offline jxrd

  • Enthusiast
  • Posts: 225
    • View Profile
Re: What is the point of MD5?
« Reply #80 on: June 14, 2009, 06:40:32 PM »
Without salt you can crack with rainbow tables though...
Logged

Offline Daniel0

  • Administrator
  • 'Insane!'
  • *
  • Posts: 11,815
  • Gender: Male
  • ^bb|[^b]{2}$
    • View Profile
Re: What is the point of MD5?
« Reply #81 on: June 14, 2009, 06:57:55 PM »
You know, I could write a long post now, or you could read this thread ;)
Logged

Offline PugJr

  • Devotee
  • Posts: 663
  • Gender: Male
  • Puggy!
    • View Profile
Re: What is the point of MD5?
« Reply #82 on: June 14, 2009, 06:59:41 PM »
Topic made May 28th...Someone needs to stop being a necromancer.
Logged

Offline MadTechie

  • Guru
  • Freak!
  • *
  • Posts: 9,374
  • Gender: Male
  • I try to F1
    • View Profile
Re: What is the point of MD5?
« Reply #83 on: June 14, 2009, 07:00:01 PM »
Quote from: jxrd on June 14, 2009, 06:40:32 PM
Without salt you can crack with rainbow tables though...
I ALWAYS recommend salt, but your statement isn't 100% true,

if you read the thread your know that.

This statement is true
Quote from: MadTechie on June 14, 2009, 06:34:03 PM
MD5 is a one-way hash function that expects a plaintext password and then outputs a hash, This hash is mathematically irreversible, meaning that it is impossible to determine the original password using only the hash.

But if your up for a challenge I'll offer the same challenge as Daniel
but without salt

here is a Pure MD5 no salt
I'll send you $50 over PayPal if you tell me what the what the plaintext value I used for this hash is:
Code: [Select]
ec81f8fe815098e02460e0184d3eac4eIt's not enough finding a string that matches the hash. You must prove that what you got is the same as what I originally had. Anyone else who wants to try can claim the $50 as well.

Now remember Daniel had salt So this should be easy for you..
Logged
Computers are good at following instructions, but not at reading your mind.
Quote from: Maq on March 11, 2009, 01:10:25 PM
The quality of a response, is usually directly related to the quality of the question. ©2009 mjdamato
Quote from: Nightslyr on February 03, 2010, 06:35:48 PM
I dunno about that.  A regular expression has a 0% chance of touching my penis.
Quote from: redarrow on October 09, 2009, 06:56:35 AM
the code is professionally made up but not working
Remember to Click Solved, how to ask questions - the smart way

Offline PugJr

  • Devotee
  • Posts: 663
  • Gender: Male
  • Puggy!
    • View Profile
Re: What is the point of MD5?
« Reply #84 on: June 14, 2009, 07:02:20 PM »
Madtechie, salt or not, if its over like 16 characters, there is no way a machine is gonna be able to brute force that.

Anyways...Could you make it $500? Maybe it'll bring the want to figure it up. ;)

Edit: Wait, wait, no how about $5000?

Edit: Oh wait a minute, we have to prove that they are matching. Thats impossible.
« Last Edit: June 14, 2009, 07:03:35 PM by PugJr »
Logged

Offline MadTechie

  • Guru
  • Freak!
  • *
  • Posts: 9,374
  • Gender: Male
  • I try to F1
    • View Profile
Re: What is the point of MD5?
« Reply #85 on: June 14, 2009, 07:06:03 PM »
LOL it doesn't matter about the length, its not possible even using brute force

Quote from: MadTechie on June 14, 2009, 07:00:01 PM
You must prove that what you got is the same as what I originally had.

we have covered all of this!

Oh and sure $5000,
How about this I'll offer $15,000 if you crack it in a week and if you don't you give me $5000 ;) but you only have 24hour to accept ;)
Logged
Computers are good at following instructions, but not at reading your mind.
Quote from: Maq on March 11, 2009, 01:10:25 PM
The quality of a response, is usually directly related to the quality of the question. ©2009 mjdamato
Quote from: Nightslyr on February 03, 2010, 06:35:48 PM
I dunno about that.  A regular expression has a 0% chance of touching my penis.
Quote from: redarrow on October 09, 2009, 06:56:35 AM
the code is professionally made up but not working
Remember to Click Solved, how to ask questions - the smart way

Offline Daniel0

  • Administrator
  • 'Insane!'
  • *
  • Posts: 11,815
  • Gender: Male
  • ^bb|[^b]{2}$
    • View Profile
Re: What is the point of MD5?
« Reply #86 on: June 14, 2009, 07:09:29 PM »
I suppose I can also reiterate one of my previous challenges in this topic.

Given a hashing function f(x) = x mod 10, my phone number inserted into that function has the output 4. Now give me a call. I'll pay fees on your phone bill and a little extra.
Logged

Offline PugJr

  • Devotee
  • Posts: 663
  • Gender: Male
  • Puggy!
    • View Profile
Re: What is the point of MD5?
« Reply #87 on: June 14, 2009, 07:15:50 PM »
Quote
LOL it doesn't matter about the length, its not possible even using brute force

Well, even assuming you didn't want proof and just wanted a match, if it was over 16, that would still be near impossible. But atleast possible.




Quote
  Now give me a call. I'll pay fees on your phone bill and a little extra.

Well lets see...Since you didn't require any proof...only...xxx-xxxx-xxx...9,999,999,999 possiblites. Heck, I'm just gonna brute force these numbers until I call daniel!

EDIT: Oops, I forgot the number format is xx-xxx-xxxx-xxx or xxx-xxx-xxxx-xxx. I forgot which one it is. Regardless, since I know he is in denmark, there can only be a max of the previous given number.
« Last Edit: June 14, 2009, 07:20:09 PM by PugJr »
Logged

Offline MadTechie

  • Guru
  • Freak!
  • *
  • Posts: 9,374
  • Gender: Male
  • I try to F1
    • View Profile
Re: What is the point of MD5?
« Reply #88 on: June 14, 2009, 07:19:11 PM »
Quote from: Daniel0 on June 14, 2009, 07:09:29 PM
I suppose I can also reiterate one of my previous challenges in this topic.

Given a hashing function f(x) = x mod 10, my phone number inserted into that function has the output 4. Now give me a call. I'll pay fees on your phone bill and a little extra.
LOL, my number is 6 my mobile is 7
anyone a 5 ?


Quote from: PugJr on June 14, 2009, 07:15:50 PM
Quote
LOL it doesn't matter about the length, its not possible even using brute force
But atleast possible.

PugJr , please tell me your joking.. as that's quite a dumb statement to make!

i have already told you
Quote
it is mathematically irreversible, meaning that it is impossible to determine the original password using only the hash.
« Last Edit: June 14, 2009, 07:20:35 PM by MadTechie »
Logged
Computers are good at following instructions, but not at reading your mind.
Quote from: Maq on March 11, 2009, 01:10:25 PM
The quality of a response, is usually directly related to the quality of the question. ©2009 mjdamato
Quote from: Nightslyr on February 03, 2010, 06:35:48 PM
I dunno about that.  A regular expression has a 0% chance of touching my penis.
Quote from: redarrow on October 09, 2009, 06:56:35 AM
the code is professionally made up but not working
Remember to Click Solved, how to ask questions - the smart way

Offline jxrd

  • Enthusiast
  • Posts: 225
    • View Profile
Re: What is the point of MD5?
« Reply #89 on: June 14, 2009, 07:21:17 PM »
Quote from: jxrd
Without salt you can crack with rainbow tables though...
Yeah, @MadTechie, that password is probably pretty random consisting of lowercase/uppercase/numbers etc.

I said you can crack MD5. But only if it's relatively simple. But tbh, who actually puts effort into making a secure password (except programmers etc)?

Most people use the same password for everything. Something like "hello" or "i love xxx". They would be crackable.
Logged
Pages: 1 2 3 4 5 [6] 7 8
« previous next »