From: Igor FOULD (igor.fould@anect.com)
Date: Sun Jan 01 2006 - 20:23:00 GMT-3
At any rate, try to take a look at the RFC 1321 that I recommended you a
day ago .... You should be able to read materials like this if you chase
a CCIE certification ... :-)))
IXF
Tim wrote:
> OK, Scott, You're on. Let me know the next time you're schedule to be in
> NY.
>
> Regarding the list: I knew I left out something. But, thanks to William
> Stallings' book, Cryptography and Network Security Principles and Practices,
> for reminding me about FCS (Frame Check Sequences) which, of course, are not
> to be confused with CRC or Checksums.
>
> (Why? I have not the slightest clue. I suspect they're just different names
> for essentially the same things designed to intimidate the casually curious
> student of networking. Do you agree?)
>
> BTW, this Stallings book is actually reasonably readable compared to most
> books on Cryptology.
>
> I'm not sure I have the time or motivation (even if I made the outrageous
> assumption I had sufficient knowledge) to write a truly professional
> document on this so maybe I'll accept the idea of magic for now. However,
> if Cisco Press asked me....
>
> OK, it's time to move on and stop blabbering....
>
> Tim
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Scott Morris
> Sent: Sunday, January 01, 2006 3:39 PM
> To: 'Tim'; security@groupstudy.com; ccielab@groupstudy.com
> Subject: RE: Hoping for Hashing Help
>
> Heheheh... I still think that "magic" is a perfectly acceptable phrase for
> many people! Like I've said, I really don't care HOW the engine in my car
> works as long as it actually does!
>
> 1. Definitely my fair share ;)
> 2. Nope, I'm an entertaining drunk. But I try not to get too wasted 'cause
> you reach a point where you don't remember the fun you're having!
>
> I think that list is a good idea, and can certainly help you in your quest
> to understand where all this magic fits in and why things are used! I say
> go for it, create the paper and I'm sure many people will sing your praises
> for it! (Or sit back and just say "mmmmmm... Magic") ;)
>
> Scott
>
> -----Original Message-----
> From: Tim [mailto:ccie2be@nyc.rr.com]
> Sent: Sunday, January 01, 2006 12:23 PM
> To: 'Scott Morris'; security@groupstudy.com; ccielab@groupstudy.com
> Subject: RE: Hoping for Hashing Help
>
> I've heard you say that before - that you can drink a lot. OK, here are 2
> q's:
>
> 1) How much can u really drink?
>
> 2) Do you get nasty when you're drunk?
>
> If you're a good drunk, then I don't care how much you drink. I say bring
> it on.
>
>
> Regarding Hashing: I was about to mention the idea of combining a shared
> key with the plaintext message to create a message digest that does more
> than just verify the integrity of the original message but then I thought
> lots not clutter too many thoughts in one post.
>
> But, since you mentioned it, I think a whole lot of people would understand
> all this stuff much better if info like this were just spelled out plainly.
>
> For example:
>
> At simplest:
>
> 1) parity
>
> What it does... How it works... Where it's used...
>
> Pros... Cons...
>
> 2) CRC
>
> What it does... How it works... Where it's used...
>
> Pros... Cons...
>
> 3) Basic Hash
>
> What it does... How it works... Where it's used...
>
> Pros... Cons...
>
> Different versions...
>
> 4) Hash with Shared secret key (HMAC)
>
>
> 5) Hash with Private Key (Digital Signature)
>
>
> I think if it's broken down like this, even (non-Einstein) people like me
> can understand it.
>
> I also wouldn't mind seeing a clear concise comparison of all these words
> that seem to mean the same thing but don't quite mean the same thing such
> as...
>
> password
>
> passphrase
>
> key
>
> secret
>
> one-time pad
>
> initialization vector
>
> and others that don't readily come to mind at the moment. With all these
> terms floating around and sometimes being misused, it's no wonder people
> find this stuff confusing.
>
> In this case, I don't think "Security by obscurity" really works. I think
> people just get turned off and decide not to deal with it. What do you
> think?
>
> Tim
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Scott Morris
> Sent: Sunday, January 01, 2006 11:02 AM
> To: 'Tim'; security@groupstudy.com; ccielab@groupstudy.com
> Subject: RE: Hoping for Hashing Help
>
> Hehehe... Be careful there, I can drink a lot! :)
>
> It's interesting sometimes! CRC is a good comparison, and that's a nice way
> to look at it. You want to make sure that something hasn't been messed with
> whether an error (CRC) or intentional. So it's more sophisticated that
> people can't hide their tacks very well. Basic parity or FEC is similar,
> but more designed to allow error correction in small chunks.
>
> One of the primary differences between MD5/SHA key exchanges and something
> like parity checking or CRC's is that often there is a starting "seed" value
> as part of the algorithm. This could be your pre-shared key, or your RSA
> key, or whatever you choose to use. But that all goes to being part of the
> sophistication. Otherwise, like with a CRC, whatever changes I may make to
> your packets I can regenerate a new CRC to make things look just fine. So
> we need to add to the sophistication and come up with "more stuff" to add in
> order to make it less likely that anyone can change things around.
>
> Cryptology is a very interesting science. I just don't have the
> inclinication to get my brain too deep into it! I used to work with a guy
> who could whiteboard out and generate MD5/SHA outputs. I'm not like that!
> (grin)
>
> Scott
>
> -----Original Message-----
> From: Tim [mailto:ccie2be@nyc.rr.com]
> Sent: Sunday, January 01, 2006 8:32 AM
> To: swm@emanon.com; security@groupstudy.com; ccielab@groupstudy.com
> Subject: RE: Hoping for Hashing Help
>
> Hey Scott,
>
> First, let me wish you and your family the best possible 2006 imaginable.
>
> And, if we do meet up sometime this year, ALL your drinks are on me. How
> much can you drink?
>
> Thanks for the reply on Hashing. I didn't know about that sampling process
> and I still don't know exactly what munging is but I get the idea.
>
> Surprisingly, this cryptology topic has turned out to be much more
> interesting than I expected.
>
> What I still don't understand is why none of the people that write about
> this Hashing stuff don't put this topic in context.
>
> When you think about it, isn't hashing just a more sophisticated form of
> parity checking which itself is a less sophisticated type of CRC (cyclic
> redundancy check)?
>
> Maybe once I fully understand all this stuff myself, I'll write a pamphlet
> geared to normal people.
>
> Thanks again, Tim
>
> -----Original Message-----
> From: Scott Morris [mailto:swm@emanon.com]
> Sent: Saturday, December 31, 2005 8:57 PM
> To: 'Tim'; security@groupstudy.com; ccielab@groupstudy.com
> Subject: RE: Hoping for Hashing Help
>
> MD5 and SHA both take a sampling of the message in question. That's why the
> message length doesn't matter much. Although, since sampling isn't a static
> thing that's why MD5 has been shown to have "collision weakness" where more
> than one input could have the same hash output even though it's not able to
> be reverse engineered.
>
> MD5 gathers its samples based on 512-bit blocks of data from the input
> message. The one-pass algorithm that takes those samples basically figures
> out how much data there is in the message and does it's magic from there!
>
> SHA-1 does a different type of sampling arrangement (different advanced
> math) and comes out with a 160-bit fingerprint. MD5 is 128-bit fingerprint.
> Both are susceptible to a collision-type attack, but SHA-1 is less affected
> by it (or it's more difficult to do), although SHA-2 has already improved
> upon the strength.
>
> Simple terms? Magic. :) I'm not sure there's much of an easier way to
> look at it. You take a chunk of data of variable size, you apply one
> algorithm to pull bits of information out, then you take another algorithm
> to munge that information and come up with a fixed-length output string.
> Any change in the message (since we go down to bit-level) can make a big
> change in the output.
>
> For some examples, wiki search for MD5 and SHA.
>
> It's math way above my brain cell structure, so I just am content to know
> the concept and accept the magic. :) I turn the key in my car and the
> engine starts. I don't particularly care why or how, it just does, and I'm
> cool with that! (grin)
>
> Cheers,
>
> Scott
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Tim
> Sent: Saturday, December 31, 2005 3:40 PM
> To: security@groupstudy.com; ccielab@groupstudy.com
> Subject: Hoping for Hashing Help
>
> Hi guys,
>
>
>
> Happy New Year.
>
>
>
> I hope everybody a year from now can look back upon 2006 and say, "This was
> truly a great year."
>
>
>
> Anyway, I've been trying to figure out something that's been bothering me
> about hashing. According to lots of sources, a hash function can take as
> input an arbitrarily long message and generate a fixed length output which
> seems to be 128 bits in length for most Hashing algorithms such as SHA-1,
> MD5, etc. commonly used today.
>
>
>
> My question is this:
>
>
>
> Can someone explain in simple terms how that's done without using advanced
> mathematics?
>
>
>
> When you think about it, this is very cool. No matter what length the
> original message is, the hash is 128 bits. If the message is 100 bytes, the
> hash is 128 bits. But, if the message is 1,000,000 bytes, the hash is still
> 128 bits. How is that possible? I'm hoping someone can illustrate how
> that's done with a simple example.
>
>
>
> Ok, everyone have a good time this evening.
>
>
>
> TIA, Tim
>
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