[cryptography] Intel RNG, questions raised by the report

Thierry Moreau thierry.moreau at connotech.com
Tue Jun 19 09:26:29 EDT 2012


Hi!

The interesting discussion induced me to look again to the actual report 
[1]. When I initially did, I came up with the impression that the RNG 
design is sound to the extent that a) any system based on sampling an 
unpredictable physical phenomenon has some intrinsic limitations, and b) 
you accept the NIST SP800-90 architecture. Furthermore, one has to read 
between the lines and make its own opinion.

Here are the main questions that I had in my first (and again in my 
subsequent) quick reading	:

Q1. Do you like a system where the deterministic algorithms 
(conditioning, DBRG) are exposed only at the pseudocode level?

Q2. If you want to build a production system with it, how do you define 
"fail-safe"? Stated otherwise, if the RNG signals its malfunction to the 
software, as a system integrator, how are you going to handle the 
negative customer perception that the the "best commercially available 
RNG" simply turns off the customer production system?

Q3. Do you agree with the report authors when they write (end of section 
3.2.1) "Also, while such failures can cause the design to behave briefly 
as a cryptographically-strong deterministic RNG, this should not result 
in any loss of security." ?

Q4. How do you get confidence that production parts are as good as the 
parts used in the report review?

None of these are specific to the Intel RNG being reviewed; any serious 
RNG arrangement based on sampling an unpredictable phenomenon might 
trigger the same set of questions.


Regards,

[1] "ANALYSIS OF INTEL’S IVY BRIDGE DIGITAL RANDOM NUMBER GENERATOR", 
prepared for intel by Mike Hamburg Paul Kocher Mark E. Marson 
Cryptography Research, Inc., March 12, 2012 
http://software.intel.com/en-us/articles/download-the-latest-bull-mountain-software-implementation-guide/

-- 
- Thierry Moreau

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