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Re: Socat vulnerability shows that crypto backdoors can be hard to spot

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On 02/04/16 18:51, William Unruh so wittily quipped:
> On 2016-02-04, Anonymous <anonymous@foto.nl1.torservers.net> wrote:
>> In article <n9018u$ufq$1@dont-email.me>
>> William Unruh <unruh@invalid.ca> wrote:
>>>
>>> On 2016-02-04, Anonymous <anonymous@foto.nl1.torservers.net> wrote:
>>>> Developers of the Socat networking tool have fixed a
>>>> cryptographic flaw that left communications open to
>>>> eavesdropping for over a year. The error is so serious that
>>>> members of the security community believe it could be an
>>>> intentional backdoor.
>>>>
>>>> http://www.csoonline.com/article/3029369/security/socat-
>>>> vulnerability-shows-that-crypto-backdoors-can-be-hard-to-
>>>> spot.html?google_editors_picks=true
>>>>
>>>
>>> It contains a stupid statement. "Checking whether a 1024-bit number is
>>> prime is doable, but is not exactly straightforward." It is very
>>> straightforward, and very doable (RSA key generation does 10s to 100s in a
>>> very short time.) While probabilistic even deterministic checking is not
>>> that hard. Certainly the lesson is that a long term key should be
>>> checked by someone other than the proposer.
>>
>> Couldn't you just fix this yourself by generating a new key and 
>> using it?
> 
> Both sides need to use the same prime. In this case I guess they insist
> on both using their "prime" (which is public knowledge). But their prime
> was not prime meaning that deriving g^ab from g^a and g^b (all mod p, the
> so called prime) became easier. Ie, no they want you to use theirs. 
> 
>>
>>> I did not even know that DH would work with a non-prime key. RSA I
>>> believe would fall over if you used a non-prime key.
> 
> I guess it does work. All you use p for is to generate a key which you
> can use in some other program (eg AES).
> 
> In RSA you actually use the primes to encrypt, and if they are not
> primes, there is a chance (how big?) that the decryption of the
> encryption will not give the original message. 

I suspect it's actually simpler than that - multiple key solutions for
non-prime [hence, non-secure]

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Socat vulnerability shows that crypto backdoors can be hard to spot Anonymous <anonymous@foto.nl1.torservers.net> - 2016-02-04 02:16 -0500
  Re: Socat vulnerability shows that crypto backdoors can be hard to spot William Unruh <unruh@invalid.ca> - 2016-02-04 17:20 +0000
    Re: Socat vulnerability shows that crypto backdoors can be hard to spot Anonymous <anonymous@foto.nl1.torservers.net> - 2016-02-04 16:54 -0500
      Re: Socat vulnerability shows that crypto backdoors can be hard to spot William Unruh <unruh@invalid.ca> - 2016-02-05 02:51 +0000
        Re: Socat vulnerability shows that crypto backdoors can be hard to spot Big Bad Bob <BigBadBob-at-mrp3-dot-com@testing.local> - 2016-02-05 11:17 -0800
          Re: Socat vulnerability shows that crypto backdoors can be hard to spot William Unruh <unruh@invalid.ca> - 2016-02-05 21:15 +0000
            Re: Socat vulnerability shows that crypto backdoors can be hard to spot Big Bad Bob <BigBadBob-at-mrp3-dot-com@testing.local> - 2016-02-05 18:07 -0800
              Re: Socat vulnerability shows that crypto backdoors can be hard to spot William Unruh <unruh@invalid.ca> - 2016-02-06 02:53 +0000
                Re: Socat vulnerability shows that crypto backdoors can be hard to spot Big Bad Bob <BigBadBob-at-mrp3-dot-com@testing.local> - 2016-02-05 21:22 -0800
                Re: Socat vulnerability shows that crypto backdoors can be hard to spot William Unruh <unruh@invalid.ca> - 2016-02-06 16:36 +0000
                Re: Socat vulnerability shows that crypto backdoors can be hard to spot Nathan Hale <nobody@remailer.org.uk> - 2016-02-07 07:28 +0000
                Re: Socat vulnerability shows that crypto backdoors can be hard to spot Anonymous <nobody@mixmin.net> - 2016-02-28 02:18 +0000
                Re: Socat vulnerability shows that crypto backdoors can be hard to spot Anonymous <anonymous@foto.nl1.torservers.net> - 2016-02-27 23:27 -0500
                Re: Socat vulnerability shows that crypto backdoors can be hard to spot Anonymous <nobody@mixmin.net> - 2016-03-01 04:42 +0000
  Re: Socat vulnerability shows that crypto backdoors can be hard to spot Anonymous <nobody@mixmin.net> - 2016-02-24 21:47 +0000
    Re: Socat vulnerability shows that crypto backdoors can be hard to spot Nathan Hale <nobody@remailer.org.uk> - 2016-02-25 06:40 +0000

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