256-bit vs 512-bit strength security

Gideon Avida gideon at decru.com
Thu Sep 13 12:35:38 PDT 2007

* From the T10 Reflector (t10 at t10.org), posted by:
* "Gideon Avida" <gideon at decru.com>
Hi Kevin (and everyone else...),
As I said in Colorado Springs, this isn't about cryptography but rather
about policies.
For example, CNSS Policy No. 15, Fact Sheet No. 1 - National Policy on
the Use of the Advanced Encryption Standard (AES) to Protect National
Security Systems and National Security Information
(http://www.cnss.gov/Assets/pdf/cnssp_15_fs.pdf) says:
The design and strength of all key lengths of the AES algorithm (i.e.,
128, 192 and 256) are sufficient to protect classified information up to
the SECRET level. TOP SECRET information will require use of either the
192 or 256 key lengths.
The NSA took it further in Suite B
(http://www.nsa.gov/ia/industry/crypto_suite_b.cfm) by specifying the
algorithms to use for encryption (AES), digital signatures and key
exchange (ECC based) and hashing (SHA). They also say there: "NSA has
determined that beyond the 1024-bit public key cryptography in common
use today, rather than increase key sizes beyond 1024-bits, a switch to
elliptic curve technology is warranted."
We've found that many non-government customers refer to these documents
for guidance. We've also found that they prefer to not have to classify
their information and to simplify things would like to use AES-256 to be
on the safe side. They also like to use the same level security
throughout the datacenter so they don't have to justify using lower
levels of security in some areas of the datacenter to the auditors.
Hope this helps the undecided crowd (and maybe convert a few from the
128 bit crowd...)
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Kevin D
Sent: Thursday, September 13, 2007 11:20 AM
To: Ralph Weber
Cc: owner-t10 at t10.org; 't10 at t10.org'
Subject: Re: 256-bit vs 512-bit strength security
I would like to share what Hugo Krawczyk, one of IBM's cryptographers
has shared with me. 
The 256-strength suite is total overkill. 
There is no need to use AES with 256-bit key today or SHA-512. 
Of course, the 128-bit suite may be broken next month (or in 5 years)
but the same is possible 
for the 256-bit suite. Actually, who said 500-bit EC will not turn out
to have only 128 bit of security in a 
breakthrough cryptanalysis in 5-10 years (or next month)? 
Given the information we have today, the 128-bit suite is good enough
for almost all commercial applications. 
If you need security of your data for the next 50 years you may consider
going to a stronger suite, but then 
(again) who said that the 256-bit will suffice? (for 50 year security I
recommend sending it inside a physical safe :) 
The only reason I see now for going for a 256-bit suite is to promote
That may or may not be a good idea, but it should be clear that that's
the only relevant reason for this suite. 
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
Ralph Weber <roweber at IEEE.org> 
Sent by: owner-t10 at t10.org 
09/12/2007 07:25 PM 
	"'t10 at t10.org'" <t10 at t10.org> 
	256-bit vs 512-bit strength security
* From the T10 Reflector (t10 at t10.org), posted by:
* Ralph Weber <roweber at ieee.org>
On Wednesday afternoon in Vancouver, you will be asked
to vote your company's position on a choice between
mandating 256-bit strength security or 512-bit strength
security in SPC-4.
If you do not yet know your company's position,
now would be a good time to start asking some
embarrassing questions.
All the best,
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