From: Anonymous <nowhere@bsu-cs.bsu.edu>
Date: Sat, 30 Jul 94 05:40:49 PDT
To: cypherpunks@toad.com
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Muchas apologies for the forwarded post, but I thought you folks might
find this of interest...



From: Perillo@dockmaster.ncsc.mil
Newsgroups: comp.security.misc
Subject: Fwd: SHA, Proposed Modification.
Date: 29 Jul 1994 10:03:21 -0400
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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
___________________________________________________________________