[Cryptography] Embedded device key generation problems due to bad PRNGs
Bill Frantz
frantz at pwpconsult.com
Mon Nov 4 23:23:15 EST 2013
<https://freedom-to-tinker.com/blog/nadiah/new-research-theres-no-need-panic-over-factorable-keys-just-mind-your-ps-and-qs/>
describes net scans for bad RSA keys on the web performed by
Zakir Durumeric, Eric Wustrow, Alex Halderman, and Nadia
Heninger. Among their conclusions:
We manually verified that 59,000 duplicate keys were repeated
due to entropy problems, representing 1% of all certificates, or
2.6% of self-signed certificates. We also found that 585,000
certificates, or 4.6% of all devices used the default
certificates pre-installed on embedded devices.
More surprisingly, we discovered that entropy problems can allow
a remote attacker with no special access to factor a significant
fraction of the RSA keys in use on the Internet. We were able to
factor 0.4% of the RSA keys in our SSL scan. We did this by
computing the greatest common divisor (GCD) of all pairs of
moduli from RSA public keys on the Internet.
However, there’s no need to panic as this problem mainly
affects various kinds of embedded devices such as routers and
VPN devices, not full-blown web servers.
The list of vulnerable devices that we have already identified
includes more than thirty different manufacturers, including
almost all of the biggest names in the computer hardware
industry. The kinds of products that we identified include
firewalls, routers, VPN devices, remote server administration
devices, printers, projectors, and VOIP phones.
This is a problem, but it’s not something that average users
need to worry about just yet. However, embedded device
manufacturers have a lot of work to do, and some system
administrators should be concerned. This is a wake-up call to
the security community, and a reminder to all of how security
vulnerabilities can sometimes be hiding in plain sight.
Cheers - Bill
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