Hi Ed,
Knowing very little about any of this cryptography stuff, I have no
idea what value of nBytes is enough. I think the wisdom, though, is
that it depends upon your situation. From what I've read, the whole
purpose of cryptography is to make it too difficult for an attacker
to succeed with an attack. Obviously, how much effort you have to
make to thwart an attack depends to a significant degree upon how
much effort the attacker is willing to make. That would depend upon
how valuable the information is, etc. In my particular application
of SSL, I don't think the information being transferred is terribly
sensitive. So I just chose to use RAND_screen() on Windows to seed
the PRNG. Although Viega, et. al., page 99 (Network Security with
OpenSSL, O'Reilly), makes it clear that he thinks RAND_screen() is a
poor choice at best, it is described as using a hash of the current
screen scan-lines for entropy. I'm no math wiz, but it's hard for me
to see how any attacker could determine what the results of that are,
regardless of effort. Perhaps if the attacker can see the screen...
I conclude that with cryptography, as with other things in life, we
all just have to decide when enough is enough and move on.
Steve
Not exactly open source, but
http://www.intel.com/design/security/rng/rng-capi.htm Accessing the Intel®
Random Number Generator through a CSP for Microsoft* CryptoAPI describes
how to access the Intel *hardware* RNG. Might be of some use to you on
Windows platforms. (I believe some *NIXs use the same hardware to populate
/dev/random when on Intel platforms.)
Edward
Chan
[EMAIL PROTECTED] To:
[EMAIL PROTECTED]
Sent by:
cc:
owner-openssl-users@ Subject: Re:
anybody using
EGADS?
openssl.org
10/22/2002 01:13
PM
Please respond
to
openssl-users
Hi Stephen,
Thanks for the reply. You're absolutely right. It
does appear that I am not blocked indefinitely...it
certainly does take a while to gather entropy. I was
using nBytes = 1024. Then I tried 512. Still very
long time.
Any suggestions on what a number should be for
acceptable randomness?
Does anybody have any alternative suggestions? Does
anybody know how Apache seeds the OpenSSL PRNG on
Windows? I think Apache uses OpenSSL don't they?
Thanks,
Ed
--- Stephen G. Schoggen [EMAIL PROTECTED]
wrote:
Ed,
I tried EGADS on Windows (PIII 866) and found that
it's time to
'gather entropy' was noticeable beyond nBytes=4. So
if you use a
relatively large nBytes, then it would appear to
block.
Steve
Hi there,
Is anybody using EGADS on Windows? I'm having a
problem using it. I've downloaded the source and
built everything. The egads service is running.
I've
written a program that links with egads.dll. I
have a
function that tries to see the OpenSSL PRNG :
bool seedPRNG(int nBytes)
{
prngctx_t ctx;
int nError;
egads_init(ctx, 0, 0, nError);
if (nError != 0)
{
DEBUG_TRACE1(_T(egads_init() failed : %d (Is
egads
service running???)), nError);
return false;
}
char* pBuf = new char[nBytes + 1];
egads_entropy(ctx, pBuf, nBytes, nError);
bool bOK = (0 == nError);
if (bOK)
{
RAND_seed(pBuf, nBytes);
}
delete [] pBuf;
egads_destroy(ctx);
return bOK;
}
However
