[From the NIST Computer Security Bulletin Board]



FEDERAL INFORMATION
PROCESSING STANDARDS PUBLICATION 185

1994 February 9




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






ESCROWED ENCRYPTION STANDARD














CATEGORY:  TELECOMMUNICATIONS   SECURITY






U.S. DEPARTMENT OF COMMERCE, Ronald H. Brown, Secretary
NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY,
Arati Prabhakar, Director


                          
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 an encryption/decryption algorithm and a
Law Enforcement Access Field (LEAF) creation method which may be
implemented in electronic devices and used for protecting
government telecommunications when such protection is desired.  The
algorithm and the LEAF creation method are classified and are
referenced, but not specified, in the standard.  Electronic devices
implementing this standard may be designed into cryptographic
modules which are integrated into data security products and
systems for use in data security applications.  The LEAF is used in
a key escrow system that provides for decryption of
telecommunications when access to the telecommunications is
lawfully authorized. 

Key words:  Cryptography, Federal Information Processing Standard,
encryption, key escrow system,  security.



                                                  FIPS PUB 185


Federal Information
Processing Standards Publication 185

1994 February 9 

Announcing the

Escrowed Encryption Standard (EES)


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:  Escrowed Encryption  Standard (EES).

Category of Standard: Telecommunications Security.

Explanation: This Standard specifies use of a symmetric-key
encryption (and decryption) algorithm (SKIPJACK) and a Law
Enforcement Access Field (LEAF) creation method (one part of a key
escrow system) which provides for decryption of encrypted
telecommunications when interception of the telecommunications is
lawfully authorized.  Both the SKIPJACK algorithm and the LEAF
creation method are to be implemented in electronic devices (e.g.,
very large scale integration chips).  The devices may be
incorporated in security equipment used to encrypt (and decrypt)
sensitive unclassified telecommunications data.  Decryption of
lawfully intercepted telecommunications may be achieved through the
acquisition and use of the LEAF,  the decryption algorithm  and 
the two escrowed key components. 

One definition of "escrow" means that something (e.g., a document,
an encryption key)  is "delivered to a third person to be given to
the grantee only upon the fulfillment of a condition" (Webster's
Seventh New Collegiate Dictionary).  The term, "escrow", for
purposes of this standard, is restricted to this dictionary
definition. 

A key escrow system, for purposes of this standard,  is one that
entrusts the two components comprising  a cryptographic key (e.g.,
a device unique key) to two  key component holders (also called
"escrow agents").  In accordance with the above definition of
"escrow", the key component holders provide the components of a key
to a "grantee" (e.g., a law enforcement official) only upon
fulfillment of the condition that the grantee has properly
demonstrated legal authorization to conduct electronic surveillance
of telecommunications which are encrypted using the specific device
whose device unique key  is being requested.  The key components
obtained through this process are then used by the grantee to
reconstruct the device unique key and obtain the session key  which
is then used to  decrypt the telecommunications that are encrypted
with that session key. 

The SKIPJACK encryption/decryption algorithm has been approved for
government applications requiring encryption of sensitive but
unclassified data telecommunications as defined herein.  The
specific operations of the SKIPJACK algorithm and the LEAF creation
method are classified and hence are referenced, but not specified,
in this standard.

Data for purposes of this standard includes voice, facsimile and
computer information communicated in a telephone system.  A
telephone system for purposes of this standard is limited to a
system which is circuit switched and operating at data rates of
standard commercial modems over analog voice circuits or which uses
basic-rate ISDN or a similar grade wireless service.

Data that is considered sensitive by a responsible authority should
be encrypted if it is vulnerable to unauthorized disclosure during
telecommunications.  A risk analysis should be performed under the
direction of a responsible authority to determine potential threats
and risks.  The costs of providing encryption using this standard
as well as alternative methods and their respective costs should be
projected.  A responsible authority should then make a decision,
based on the risk and cost analyses, whether or not to use
encryption and then whether or not to use this standard.

Approving Authority:  Secretary of Commerce.

Maintenance Agency: Department of Commerce, National Institute of
Standards and Technology.

Applicability:   This standard is applicable to all Federal
departments and agencies and their contractors under the conditions
specified below.  This standard may be used in designing and
implementing security products and systems, which Federal
departments and agencies use or operate or which are operated for
them under contract.  These products may be used when replacing
Type II and Type III (DES) encryption devices and products owned by
the government and government contractors.  

This standard may be used  when the following conditions apply:

     1.  An authorized official or manager responsible for data
security or the security of a computer system decides that
encryption is required and cost justified as per OMB Circular A-
130; and
     2.  The data is not classified according to Executive Order
12356, entitled "National Security Information," or to its
successor orders, or to the Atomic Energy Act of 1954, as amended. 


However, Federal departments or agencies which use encryption
devices for protecting data that is classified according to either
of these acts may use those devices also for protecting
unclassified data in lieu of this standard. 

In addition, this standard may be adopted and used by non-Federal
Government organizations.  Such use is encouraged when it provides
the desired security.

Applications: This standard may be used in any unclassified
government and commercial communications.  Use of devices
conforming to this standard is voluntary for unclassified
government applications and for commercial security applications.

Implementations:   The encryption/decryption algorithm and the LEAF
creation method shall be implemented in electronic devices (e.g.,
electronic chip packages) which are protected against unauthorized
entry, modification and reverse engineering.  Implementations which
are tested and validated by NIST will be considered as complying
with this standard.  An electronic device shall be incorporated
into a cryptographic module in accordance with FIPS 140-1.  NIST
will test for conformance with FIPS 140-1.  Conforming
cryptographic modules can then be integrated into security
equipment for sale and use in a security application.  Information
about devices that have been validated,  procedures for testing
equipment for conformance with NIST standards, and information
about approved security equipment are available from  the Computer
Systems Laboratory, NIST, Gaithersburg, MD 20899.

Export Control: Implementations of this standard are subject to
Federal Government export controls as specified in Title 22, Code
of Federal Regulations, Parts 120 through 131 (International
Traffic of Arms Regulations - ITAR).  Exporters of encryption
devices, equipment and technical data are advised to contact the
U.S. Department of State, Office of Defense Trade Controls for more
information.

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

Implementation Schedule: This standard becomes effective thirty
days following publication of this FIPS PUB.

Specifications: Federal Information Processing Standard (FIPS 185),
Escrowed Encryption Standard (EES) (affixed).

Cross Index:

   a.  FIPS PUB 46-2, Data Encryption Standard.
   b.  FIPS PUB 81, Modes of Operation of the DES
   c.  FIPS PUB 140-1,  Security Requirements for Cryptographic
Modules.




 GLOSSARY:

The following terms are used as defined below for purposes of this
standard:

Data - Unclassified voice, facsimile and computer information
communicated over a telephone system. 
 
Decryption - Conversion of ciphertext to plaintext through the use
of a cryptographic algorithm.

Device (cryptographic) -  An electronic implementation of the
encryption/decryption algorithm and the LEAF creation method as
specified in this standard.

Digital data - Data that have been converted to a binary
representation.

Encryption - Conversion of plaintext to ciphertext through the use
of a cryptographic algorithm.

Key components  - The  two values from which a key can be derived
(e.g., KU1 ~ KU2).  

Key escrow - The processes of managing (e.g., generating, storing,
transferring, auditing) the two components of a cryptographic key
by two key component holders.

LEAF Creation Method  - A part of a key escrow system that is
implemented in a cryptographic device and creates a Law Enforcement
Access Field.

Type I cryptography - A cryptographic algorithm or device approved
by the National Security Agency for protecting classified
information.

Type II cryptography - A cryptographic algorithm or device approved
by the National Security Agency for protecting sensitive
unclassified information in systems as specified in section 2315 of
Title 10 United States Code, or section 3502(2) of Title 44, United
States Code.

Type III cryptography - A cryptographic algorithm or device
approved as a Federal Information Processing Standard.

Type III(E) cryptography - A Type III algorithm or device that is
approved for export from the United States.
 
Qualifications: The protection provided by a security product or
system is dependent on several factors.  The protection provided by
the SKIPJACK algorithm against key search attacks is greater than
that provided by the DES algorithm (e.g., the cryptographic key is
longer).  However, provisions of this standard are intended to
ensure that information encrypted through use of devices
implementing this standard can be decrypted by a legally authorized
entity. 


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 185
(FIPS PUB 185), 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.


Federal Information
Processing Standards Publication 185

1994 February 9


Specifications for the


ESCROWED ENCRYPTION STANDARD


1. INTRODUCTION

This publication specifies Escrowed Encryption Standard (EES) 
functions and parameters.

2. GENERAL

This standard specifies use of the SKIPJACK cryptographic algorithm
and a LEAF Creation Method to be implemented in an approved
electronic device (e.g., a very large scale integration electronic
chip).  The device is contained in a logical cryptographic module
which is then integrated in a  security product for encrypting and
decrypting telecommunications.
 
Approved implementations may be procured by authorized
organizations for integration into security equipment.  Devices
must be tested and validated by NIST for conformance to this
standard.  Cryptographic modules must be tested and validated by
NIST for conformance to FIPS 140-1. 

3.  ALGORITHM SPECIFICATIONS

The specifications of the encryption/decryption algorithm
(SKIPJACK) and LEAF Creation Method 1 (LCM-1) are classified.  The
National Security Agency maintains these classified specifications
and approves the manufacture of devices which implement the
specifications.   NIST tests for conformance of the devices
implementing this standard in cryptographic modules to FIPS 140-1
and FIPS 81. 

4.  FUNCTIONS  AND PARAMETERS 

 4.1   FUNCTIONS

     The following functions, at a minimum, shall be implemented:

     1.  Data Encryption:  A session key (80 bits) shall be used to
encrypt plaintext information in one or more of the following modes
of operation as specified in FIPS 81:  ECB, CBC, OFB (64), CFB (1,
8, 16, 32, 64).

     2.  Data Decryption:   The session key (80 bits) used to
encrypt the data shall be used to decrypt resulting ciphertext to
obtain the data .

     3.  LEAF Creation:  A Family Key (e.g., KF-1) shall be used to
create a Law Enforcement Access Field (LEAF) in accordance with a
LEAF Creation Method (e.g., LCM-1).  The security equipment shall
ensure that the LEAF is transmitted in such a manner that the LEAF
and ciphertext may be decrypted with legal authorization.  No
additional encryption or modification of the LEAF is permitted. 

4.2  PARAMETERS

     The following parameters shall be used in performing the
prescribed functions:

     1.  Device Unique Identifier  (UID):  The identifier unique to
a particular device and used by the Key Escrow System.

     2.  Device Unique Key (KU):  The cryptographic key unique to
a particular device and used by the Key Escrow System.

     3.  Cryptographic Protocol Field (CPF):  The field identifying
the registered cryptographic protocol used by a particular
application and used by the Key Escrow System (reserved for future
specification and use).

     4.   Escrow Authenticator (EA):  A binary pattern that is
inserted in the LEAF to ensure that the LEAF is transmitted and
received properly and has not been modified, deleted or replaced in
an unauthorized manner.

     5.  Initialization Vector (IV):  A mode and application
dependent vector of bytes used to initialize, synchronize and
verify the encryption, decryption and key escrow functions.

     6.  Family Key (KF):  The cryptographic key stored in all
devices designated as a family that is used to create a LEAF.

     7.  Session Key (KS):  The cryptographic key used by a device
to encrypt and decrypt data during a session. 

     8.   Law Enforcement Access Field (LEAF):  The field
containing the encrypted session key and the device identifier and
the escrow authenticator. 


5.   IMPLEMENTATION

The Cryptographic Algorithm (i.e., SKIPJACK) and a LEAF Creation
Method (e.g., LCM-1) shall be implemented in an electronic device
(e.g., VLSI chip) which is highly resistant to reverse engineering
(destructive or non-destructive) to obtain or modify the
cryptographic algorithm, the UID, the KF, the KU, the EA, the CPF,
the operational KS, and any other security or Key Escrow System
relevant information.  The device shall be able to be
programmed/personalized (i.e., made unique) after mass production
in such a manner that the UID, KU (or its components), KF (or its
components) and EA fixed pattern can be entered once (and only
once) and maintained without external electrical power. 

The LEAF and the IV shall be transmitted with the ciphertext.  The
specifics of the protocols used to create and transmit the LEAF,
IV, and encrypted data shall be registered and a CPF assigned.  The
CPF  (and the KF-ID, LCM-ID) shall then be transmitted in
accordance with the registered specifications.

Various devices implementing this standard are anticipated.  The
implementation may vary with the application.  The specific
electric, physical and logical interface will vary with the
implementation.  Each approved, registered implementation shall
have an unclassified electrical, physical and logical interface
specification sufficient for an equipment manufacturer to
understand the general requirements for using the device.  Some of
the requirements may be classified and therefore would not be
specified in the unclassified interface specification.  
 
The device Unique Key shall be composed of two components (each a
minimum of 80 bits long) and each component shall be independently
generated and stored by an escrow agent.  The session key used to
encrypt transmitted information shall be the same as the session
key used to decrypt received information in a two-way simultaneous
communication.  The Lead Creation Method (LCM), the Cryptographic
Protocol Field (CPF), and the Family Key Identifier (KF-ID) shall
be registered in the NIST Computer Security Object Register.  

This standard is not an interoperability standard.  It does not
provide sufficient information to design and implement a security
device or equipment.  Other specifications and standards will be
required to assure interoperability of EES devices in various
applications.  Specifications of a particular EES device must be
obtained from the manufacturer.

The specifications for the SKIPJACK algorithm are contained in the
R21 Informal Technical Report entitled "SKIPJACK" (S), R21-TECH-
044-91, May 21, 1991.  The specifications for LEAF Creation Method
1 are contained in the R21 Informal Technical Report entitled "Law
Enforcement Access Field for the Key Escrow Microcircuit" (S).  
Organizations holding an appropriate security clearance and
entering into a Memorandum of Agreement with the National Security
Agency regarding implementation of the standard will be provided
access to the classified specifications.   Inquiries may be made
regarding the Technical Reports and this program to Director,
National Security Agency, Fort George G. Meade, MD 20755-6000,
ATTN: R21.




