[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Snake Oil FAQ 0.4 [comments appreciated]

For those not-yet-in-the-know: I no longer have the time to manage it 
and asked for somebody (and Matt agreed to) to take the Snake Oil
FAQ's care and feeding.

Note that this is not cc'd to coderpunks. I don't 
think it's appropriate for coderpunks.

On 16 Sep 96 at 9:56, C Matthew Curtin wrote:
> --------------------------- snake-oil-faq ----------------------------
>                            Snake-Oil Warning Signs
>                         Encryption Software to Avoid
> The Snake Oil FAQ is (to be) posted monthly to cypherpunks, sci.crypt,
> alt.security, comp.security, and comp.infosystems. We're targeting those who

Does it need to be posted monthly?  Better to post pointers to it 
most of the time, possibly to other places as well  (alt.2600 comes
to mind...).

Perhaps when the first 'non-beta' of this document is released a 
History could be added.

> Different products will serve different needs, and it's rare that a product
> will serve every need. (Sometimes a product won't be needed: it may be

Nitpick: Hm. Change that to "no product will serve every need".

> better to use a utility to encrypt files, transmit them over a network using
> standard file transfer tools, and decrypt them at the other end than to use
> a separate encrypted utility in some cases.)

Or more clearly: is encryption THE feature of the utility, or is it 
an added feature?  It's better to use separate utilities made for 
that purpose rather than one that tries to do everything.
> Key Sizes
> Some ciphers, while currently secure against most attacks, are not
> considered viable in the next few years because of relatively small keysizes
> and increasing processor speeds (making a brute-force attacks feasible). The

Change to "making brute force attacks--that is, trying every possible 

>                     Symmetric and Public-Key Lengths With
>                   Similar Resistance to Brute-Force Attacks
>                  Symmetric Key Length Public-key Key Length
>                         56 bits             384 bits
>                         64 bits             512 bits
>                         80 bits             768 bits
>                        112 bits             1792 bits
>                        128 bits             2304 bits

That's a controversial comparison. I've read references (from a 
couple of years ago) saying that a 3k-bit RSA key is as strong as a 
128-bit IDEA key.

Trying to compare the two (symmetric and assymetric) is like running 
through a tar pit.

> Some Common Snake-Oil Warning Signs
> The following are some of the "red flags" one should watch for when
> examining an encryption product
>    * Technobabble
>      A sign of technobabble is a descrption which drops a lot of technical
>      terms for how the system works without actually explaining how it
>      works. Often specifically coined terms are used to describe the scheme
>      which are not found in the literature.

Of course, how is an amateur supposed to know if these terms are 
found in the literature? That was a recurring comment that people 
sent me when I first posted the FAQ.
>      Just because software uses to different method of computation 

Typo! "uses to different method..."?
>      grounded in mathematical theory. The security is based on problems that
>      are believed, if not known to be hard to solve.

Hm. How about "that are widely believed"?
>      A OTP system is not an algorithm. It works by having a "pad" of
>      random bits in the possession of both the sender and recipient.
>      never again be used. The bits in the pad must be truly random,
>      generated using a real random source, such as specialized
>      hardware, radioactive decay timings, etc., and not from an
>      algorithm or cipher. Anything else is not a one-time-pad.

Although it is(?) mentioned below, I'd emphasize here in some way that 
the users of the OTP generate the key.  Somebody else sending you a 
supposed OTP that he generated is not secure.

>      The vendor may confuse random session keys or initialization vectors
>      with OTPs.

Explain random session keys and initialization vectors.  A glossary 
at the end of the document would be a good thing.

>      Sometimes attacks are theoretical or impractical (requiring special
>      circumstances or massive computing power running for many years), and
>      it's easy to confuse a layman by mentioning these.

Oh yeah.  These need to be explained.  What I had in mind was timing 
attacks against RSA or IDEA, or factoring of public keys.

>    * Keys and Passwords
>      The "key" and the "password" are often not the same thing. The "key"

"often" not?!? (oops...was that my wording?) They aren't the same, 
though often they are confused in snake oil.

>      If there's a third-party utility that can crack the software,
>      avoid it.
>      If the vendor claims it can recover lost passwords (without using a
>      key-backup or escrow feature), avoid it.
>      If there is a key-backup or escrow feature, are you in control
>      of the backup, or does the vendor or someone else hold a copy
>      of the key?

That is, if you lose the key, you don't want a third party to have as 
much a chance to recover it as you do.

>      If the vendor is unaware of export restrictions, avoid the software:
>      the vendor is not familiar with the state of the art.

Also... if the vendor does not understand export restrictions, avoid 
the software. I'm thinking of a certain snoil-vendor who said 128-bit 
IDEA keys were'nt secure since they could be exported.

>      Because of export restrictions, some legitimate (not-Snake Oil)
>      products may have a freely exportable version for outside of the USA,
>      which is different from a separate US/Canada-only distribution. Also

Such exportable versions are not as secure, of course.
> Other Considerations
> Interface isn't everything: user-friendliness is an important factor, but if
> the product isn't secure then you're better off with something that is
> secure (if not as easy to use).
> No product is secure if it's not used properly. You can be the weakest link
> in the chain if you use a product carelessly. Do not trust any product to be
> foolproof, and be wary any product that claims it is.

I wanted to add some sort of 'non-guru hacks' to test a product. One 
example might be to actually examine 'encrypted' files to see if they 
are really encrypted. (I'm thinking of the AMG archiver, which only 
encrypted the CRC; CODEC archiver also only encrypted the CRC is a 
file is not compressed.)

Thanks again for taking over the FAQ.  A good job!

No-frills sig. Befriend my mail filter by sending a message with the subject "send help"
Key-ID: 5D3F2E99 1996/04/22 [email protected] ([email protected])
Send a message with the subject "send pgp-key" for a copy of my key.