Cryptography and the Open Source Security Debate

[Ben Laurie]

lrk wrote:

> On Thu, Aug 12, 2004 at 03:27:07PM -0700, Jon Callas wrote:
> 
>>On 10 Aug 2004, at 5:16 AM, John Kelsey wrote:
>>
>>
>>>So, how many people on this list have actually looked at the PGP key 
>>>generation code in any depth?  Open source makes it possible for 
>>>people to look for security holes, but it sure doesn't guarantee that 
>>>anyone will do so, especially anyone who's at all good at it.
>>
>>Incidentally, none of the issues that lrk brought up (RSA key being 
>>made from an "easy to factor" composite, a symmetric key that is a weak 
>>key, etc.) are unique to PGP.
> 
> 
> Yep. And I know that. But as my hair turns grey, I make more simple mistakes
> and catch fewer of them.
> 
> 
> Looks like we are batting zero here. I have seen no responses nor received
> off-list e-mail from anyone admitting to examining the open source for holes.
> 
> 
> My examination of RSAREF and OpenSSL code was more toward understanding how
> they handled big numbers. It appears both generate prime numbers which are
> half the length of the required N and with both of the two most significant
> bits set to one. This means the ratio R=P/Q (P being the larger prime) is
> limited to 1<R<(4/3). The actual maximum R is less and can be determined
> by examining N.

This doesn't sound right to me - OpenSSL, IIRC, sets the top and bottom 
bits to 1. Of course, all large primes have the bottom bit set to one.

Cheers,

Ben.

-- 
http://www.apache-ssl.org/ben.html       http://www.thebunker.net/

"There is no limit to what a man can do or how far he can go if he
doesn't mind who gets the credit." - Robert Woodruff

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