                                                     FIPS PUB 180

                                              FEDERAL INFORMATION
                                 PROCESSING STANDARDS PUBLICATION

                                                    1993 May 11  

U.S. DEPARTMENT OF COMMERCE/National Institute of Standards and Technology

                      SECURE HASH STANDARD

   /*** NOTE: NOT OFFICIAL. HARD COPY IS THE OFFICIAL VERSION.
        ^ is used for exponentiation or superscript. ***/

                  CATEGORY:  COMPUTER SECURITY

    U.S. DEPARTMENT OF COMMERCE, Barbara Franklin, Secretary
         NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

                               Foreword

   The Federal Information Processing Standards Publication Series
of the National Institute of Standards and Technology (NIST) is the
official series of publications relating to standards and
guidelines adopted and promulgated under the provisions of Section
111(d) of the Federal Property and Administrative Services Act of
1949 as amended by the Computer Security Act of 1987, Public Law
100-235.  These mandates have given the Secretary of Commerce and
NIST important responsibilities for improving the utilization and
management of computer and related telecommunications systems in
the Federal Government.  The NIST, through the Computer Systems
Laboratory, provides leadership, technical guidance, and
coordination of Government efforts in the development of standards
and guidelines in these areas. 

   Comments concerning Federal Information Processing Standards
Publications are welcomed and should be addressed to the Director,
Computer Systems Laboratory, National Institute of Standards and
Technology, Gaithersburg, MD 20899.

                           James H. Burrows, Director
                           Computer Systems Laboratory 

                               Abstract

   This standard specifies a Secure Hash Algorithm (SHA) which can
be used to generate a condensed representation of a message called
a message digest. The SHA is required for use with the Digital
Signature Algorithm (DSA) as specified in the Digital Signature Standard (DSS)
and whenever a secure hash algorithm is required for federal applications.
The SHA is used by both the transmitter and intended receiver of a message in
computing and verifying a digital signature.

Key words: Computer security, digital signatures,
Federal Information Processing Standard, hash algorithm.

                                                  FIPS PUB 180 

                          Federal Information
                  Processing Standards Publication 180 

                             1993 MAY 11

                            ANNOUNCING THE 

                         SECURE HASH STANDARD

Federal Information Processing Standards Publications (FIPS PUBS)
are issued by the National Institute of Standards and Technology
(NIST) after approval by the Secretary of Commerce pursuant to
Section 111(d) of the Federal Property and Administrative Services
Act of 1949 as amended by the Computer Security Act of 1987, Public
Law 100-235.

Name of Standard: Secure Hash Standard.

Category of Standard: Computer Security.

Explanation: This Standard specifies a Secure Hash Algorithm (SHA) 
for computing a condensed representation of a message or a data file. When a 
message of any length < 2^64 bits is input, the SHA produces a 160-bit output 
called a message digest.  The message digest can
then be input to the Digital Signature Algorithm (DSA) which generates or 
verifies the signature for the message (see Figure 1).  Signing the 
message digest rather than the message often
improves the efficiency of the process because the message digest is 
usually much smaller in size than the message.  The same hash algorithm 
must be used by the verifier of a digital signature
as was used by the creator of the digital signature.  The SHA is called secure 
because it is computationally infeasible to find a message which corresponds 
to a given message digest, or to find two different messages which produce the 
same message digest.  Any change to a message
in transit will, with very high probability, result in a different message 
digest, and the signature will fail to verify.  The SHA is based on principles 
similar to those used by Professor Ronald L. Rivest of MIT when designing 
the MD4 message digest algorithm ("The MD4 Message Digest 
Algorithm," Advances in Cryptology - CRYPTO '90 Proceedings, 
Springer-Verlag, 1991, pp. 303-311), and is 
closely modelled after that algorithm.

Approving Authority: Secretary of Commerce.

Maintenance  Agency:  U.S. Department of Commerce,
National Institute of Standards and Technology, Computer Systems Laboratory.

Applicability: This standard is applicable to all Federal
departments and agencies for the protection of unclassified
information that is not subject to section 2315 of Title 10, United
States Code, or section 3502(2) of Title 44, United States Code. 
This standard is required for use with the Digital Signature Algorithm
(DSA) as specified in the Digital Signature Standard (DSS)
and whenever a secure hash algorithm is required for
federal applications.  Private and commercial organizations are
encouraged to adopt and use this standard. 

Applications: The SHA may be used with the DSA in electronic mail, 
electronic funds transfer, software distribution, data storage, and other 
applications which require data integrity assurance
and data origin authentication.  The SHA may also be used whenever it is 
necessary to generate a condensed version of a message.

Implementations: The SHA may be implemented in software, firmware,
hardware, or any combination thereof.  Only implementations of the
SHA that are validated by NIST will be considered as complying with
this standard.  Information about the requirements for validating
implementations of this standard can be obtained from the National
Institute of Standards and Technology, Computer Systems Laboratory,
Attn: SHS Validation, Gaithersburg, MD 20899.

Export Control: Implementations of this standard are subject to
Federal Government export controls as specified in Title 15, Code
of Federal Regulations, Parts 768 through 799.  Exporters are
advised to contact the Department of Commerce, Bureau of Export
Administration for more information.

Patents: Implementations of the SHA in this standard may be covered
by U.S. and foreign patents.

Implementation Schedule: This standard becomes effective October 15, 1993. 

Specifications: Federal Information Processing Standard (FIPS 180)
Secure Hash Standard (affixed).

Cross Index:

   a. FIPS PUB 46-1, Data Encryption Standard.

   b. FIPS PUB 73, Guidelines for Security of Computer Applications.

   c. FIPS PUB 140-1, Security Requirements for Cryptographic Modules.

   d. FIPS PUB XX, Digital Signature Standard.

Qualifications: While it is the intent of this standard to specify
a secure hash algorithm, conformance to this standard does not
assure that a particular implementation is secure.  The responsible
authority in each agency or department shall assure that an overall
implementation provides an acceptable level of security.  This
standard will be reviewed every five years in order to assess its
adequacy.

Waiver Procedure: Under certain exceptional circumstances, the
heads of Federal departments and agencies may approve waivers to
Federal Information Processing Standards (FIPS).  The head of such
agency may redelegate such authority only to a senior official
designated pursuant to section 3506(b) of Title 44, United States
Code.  Waiver shall be granted only when:

   a. Compliance with a standard would adversely affect the       
      accomplishment of the mission of an operator of a Federal   
      computer system; or

   b. Compliance with a standard would cause a major adverse
      financial impact on the operator which is not offset by
      Government-wide savings.

Agency heads may act upon a written waiver request containing the
information detailed above.  Agency heads may also act without a
written waiver request when they determine that conditions for
meeting the standard cannot be met.  Agency heads may approve
waivers only by a written decision which explains the basis on
which the agency head made the required finding(s).  A copy of
each decision, with procurement sensitive or classified portions
clearly identified, shall be sent to: National Institute of
Standards and Technology; ATTN: FIPS Waiver Decisions, Technology
Building, Room B-154, Gaithersburg, MD 20899.

In addition, notice of each waiver granted and each delegation of
authority to approve waivers shall be sent promptly to the
Committee on Government Operations of the House of Representatives
and the Committee on Government Affairs of the Senate and shall be
published promptly in the Federal Register.

When the determination on a waiver applies to the procurement of
equipment and/or services, a notice of the waiver determination
must be published in the Commerce Business Daily as a part of the
notice of solicitation for offers of an acquisition or, if the
waiver determination is made after that notice is published, by
amendment to such notice.

A copy of the waiver, any supporting documents, the document
approving the waiver and any accompanying documents, with such
deletions as the agency is authorized and decides to make under 5
United States Code Section 552(b), shall be part of the procurement
documentation and retained by the agency.

Where to Obtain Copies of the Standard: Copies of this publication
are for sale by the National Technical Information Service, U.S.
Department of Commerce, Springfield, VA 22161.  When ordering,
refer to Federal Information Processing Standards Publication 180 
(FIPS PUB  180), and identify the title.  When microfiche is desired,
this should be specified.  Prices are published by NTIS in current
catalogs and other issuances.  Payment may be made by check, money
order, deposit account or charged to a credit card accepted by
NTIS.
