Subject: RE: iSCSI: BASE64 and numerical values

From: "Julian Satran" <[email-masked]>
Date: Tue, 21 May 2002 04:42:25 +0300

I am in the process of the reviewing the needs for large numerical values 
(based on cryptography requirements for specified and other known schemes 
that vendors may want to use). If The results will indicate that large 
numerical values are of marginal use I will drop base64 for numbers. If 
not I will leave it as is.
As for you "confusion and ambiguity in
this realm of the spec (e.g., decimal representation, leading zeroes,
definitions of field size, byte swapping issues, etc.)" I am afraid that I don't see how base64 different than hexadecimal
and I assume a statement about ordering solves both.

Julo

"Michael Krueger" <[email-masked]>
05/20/2002 10:37 PM
Please respond to "Michael Krueger"

        To:     Julian Satran/Haifa/IBM@IBMIL, <[email-masked]>
        cc: 
        Subject:        RE: iSCSI: BASE64 and numerical values

On Saturday, May 18, 2002 1:31 AM, Julian Satran wrote:
> Yes for regular numerical values it makes sense. We will have to keep
> it for large numerical values used for cryptography.  Julo

I'm glad to see that base-64 encoding will be dropped for numbers, but I'm
afraid I still have a small issue with the language being used here.  As I
understand it, "large numerical values" are NOT used for cryptography; the
keys, challenges, responses, etc., are large BINARY ITEMS*, not large
numbers.  I still believe that failing to make a distinction between 
numbers
and binary items is what's behind a lot of the confusion and ambiguity in
this realm of the spec (e.g., decimal representation, leading zeroes,
definitions of field size, byte swapping issues, etc.).

Michael

*I have no special attachment to the term "binary items"; call them 
"binary
strings," "bit patterns," or whatever you like . . . but please just don't
call them "numeric" or "numbers."

--
Michael J. Krueger              mailto:[email-masked]
Wind River Networks                         http://www.windriver.com
500 Wind River Way                               phone: 510-749-2130
Alameda, CA  94501                                 fax: 510-749-2010

---

From: Paul Koning <[email-masked]>
Date: Tue, 21 May 2002 10:02:45 -0400

> not I will leave it as is.

Diffie-Hellman and RSA are both based on arithmetic on large integers,
so clearly it is necessary to agree on which byte in the bytestring
encoding of those values is the most significant byte.

Then again, the same is true for non-numeric values: if you swap
around the bytes of an MD5 or SHA-1 cryptographic hash (as in CHAP)
things break just as badly.

> As for you "confusion and ambiguity in this realm of the spec (e.g.,
> decimal representation, leading zeroes, definitions of field size,
> byte swapping issues, etc.)" I am afraid that I don't see how base64
> different than hexadecimal and I assume a statement about ordering
> solves both.

True.

The remaining point is this: base64 is a standard encoding for octet
strings, and therefore for bignums.  It's not a commonly used encoding
for "normal size integers" i.e., 32 or 64 bit ints.

    paul