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Muchas apologies for the forwarded post, but I thought you folks might
find this of interest...
From: [email protected]
Newsgroups: comp.security.misc
Subject: Fwd: SHA, Proposed Modification.
Date: 29 Jul 1994 10:03:21 -0400
Organization: Yale CS Mail/News Gateway
Lines: 611
Sender: [email protected]
Message-ID: <[email protected]>
NNTP-Posting-Host: babyblue.cs.yale.edu
The following is the Request for Comments citation summary, on the
revision or fix of the Secure Hash Algorithm (SHA) released by
NIST on July 11th.
Enclosed is the "technical details sheet" of the
proposed modification that has been floating around NIST for the
last two months.
- Robert
----------------------------
Federal Register 07/11/94
Citation="59 FR 35317"
[Docket No. 940675-4175]
RIN 0693-AB33
Proposed Revision of Federal Information Processing Standard
(FIPS) 180, Secure Hash Standard
AGENCY: National Institute of Standards and Technology (NIST),
Commerce.
ACTION: Notice; Request for comments.
SUMMARY: A revision of Federal Information Processing Standard
(FIPS) 180, Secure Hash Standard (SHS), is being proposed. This
proposed revision corrects a technical flaw that made the standard
less secure than had been thought. The algorithm is still reliable
as a security mechanism, but the correction returns the SHS
to the original level of security.
The SHS produces a 160-bit output called a message digest
for a message of any size. This message digest can be used with
FIPS 186, Digital Signature Standard (DSS), to compute a signature
for the message. The same message digest should be obtained
by the verifier of the signature when the received version of
the message is used as input to the Secure Hash Algorithm (SHA).
--------------
Proposed Modification of the Secure Hash Algorithm
In Section 7 of [1](page 9), the line which reads
b) For t=16 to 79 let W(t) = W(t-3) XOR W(t-8) XOR W(t-14) XOR W(t-16).
is to be replaced by
b) For t=16 to 79 let
W(t) = S1( W(t-3) XOR W(t-8) XOR W(t-14) XOR W(t-16) ).
where S1 is a left circular shift by one bit as defined
in Section 3 of [1](page 6), namely
S1(X) = (X<<1) V (X>>31).
ASCII translator's note : S1 is actually, S superscript 1.
W(t-n) is actually, W subscript, t or t-n.
References:
[1] FIPS PUB 180; Secure Hash Standard
Computer Systems Laboratory
National Institute of Standards and Technology
1993 May 11
___________________________________________________________________
Robert J. Perillo, CCP Computer Scientist
Cerberus Systems Washington, DC
___________________________________________________________________