Re: Interesting Discussion with US Government Computer Expert

dsr_at_Florence.edu
Date: 08/31/03 

Date: Sat, 30 Aug 2003 23:51:19 GMT

On Fri, 29 Aug 2003 23:42:22 GMT, Russ Lyttle <lyttlec@earthlink.net>
wrote:

>No One wrote:
>
>> OK. Here's the deal. I work for the government as a consultant on SIPRNET.
>> Had a discussion with a fellow contractor who works for a government
>> agency in Maryland. (Hint, Hint).
>>
>> He implied that RSA-type keys were inherently unsecure because of known
>> plaintext attacks. That is if I have your public key and use it to
>> encrypt one or more text messages (or I guess any other data), by knowing
>> the algorithm I can calculate the private key by comparing the cipherttext
>> and the know plaintext.
>>
>> I think there has to be more to the story. Unfortunately, my knowledge of
>> this encryption stops at knowing what group (i.e. this one) to ask the
>> question in.
>>
>> There has to be more to the story, right guys?? Probably involving
>> factoring very large prime numbers?
>>
>> I don't really need to know the answer to this question, but it will
>> provide an indication of how seriously I should take anything else this
>> guy says.
>>
>> Thanks
>I think if your friend were in a position to know, he wouldn't be talking.
>Also a prime is defined as a number that can't be factored. OTOH, most key
>generators make pseudo-primes. Some one might have found a way to attack
>some RSA keys by finding factors to "weak" pseudo-primes.

More likely someone found that only a subset of pseudo random primes
would be generated. Between hash collisions and weak pseudo random
seeds the subset of probable primes might be relatively small. There
is evidence from key server managment that duplicate key generation
happens more often then it should.

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