Hi Ed,
At 06:30 02-04-2014, Edward Lewis wrote:
I found that there are two primary reasons why 1024 bits is used in
zone signing keys.
One - peer pressure. Most other operators start out with 1024
bits. I know of some cases where operators wanted to choose other
sizes but were told to "follow the flock."
Two - it works. No one has ever demonstrated a failure of a 1024
bit key to provide as-expected protection.
My short comment would be Yes to the above.
The problem might be the "follow the flock" as there is an assumption
that someone looked at the details before choosing the 1024 bit key.
What does it matter from a security perspective? DNS messages are
short lived. It's not like we are encrypting a novel to be kept
secret for 100 years. With zone signing keys lasting a month, 6
months, or so, and the ability to disallow them fairly quickly,
what's the difference between this so-called 80 or 112 bit strength
difference? Yes, I understand the doomsday scenario that someone
might "guess" my private key and forge messages. But an attack is
not as simple as forging messages, it takes the ability to inject
them too. That can be done - but chaining all these things together
just makes the attack that much less prevalent.
For context, the discussion is about a ZSK. There is a theory that
it would take under a year and several million (U.S.) dollars to
break 1024 bits. It has been said (not on this mailing list) that an
organization could do it within a shorter time. It's not a good idea
to wait for the demonstration as it can raise concerns about the
entity which chose the key.
As a general comment I tried to find out which NIST recommendations
are being discussed in respect to DNSSEC. The requirements mentioned
by Joe Abley refers to NIST SP 800-78. That document is about
"Cryptographic Algorithms and Key Sizes for Personal Identity
Verification". Is that the NIST recommendation on which this
discussion is based?
Regards,
S. Moonesamy
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