GAO United States

General Accounting Office

Washington, D.C. 20548

Accounting and Financial

Management Division

B-253174 

May 4, 1993

Mr. Charles E. Tompkins, III

Deputy Program Manager

Reserve Component Automation System

Department of the Army

Dear Mr. Tompkins:

This letter responds to your March 5, 1993, request that we sanction the

electronic authentication system used in the Reserve Component

Automation System (RCAS) for financial applications. RCAS processes

unclassified and classified data. Based on the material provided with your

letter and discussions with your staff, we have concluded that the

electronic signatures generated by this system do not provide the same

quality of evidence as the handwritten signatures they are designed to

replace. We are unable to sanction your electronic authentication system

for financial and contractual purposes because it does not provide

reasonable assurance that the signatures generated will meet the criteria

outlined in 71 Comp. Gen. l09 (1991). Specifically, we note that your

system uses cryptographic algorithms and techniques which have not been

approved by either the National Institute of Standards and Technology

(NIST) or the National Security Agency (NSA). We do not sanction systems

whose algorithms and techniques have not been approved by the

appropriate agency.

The Computer Security Act assigns to NIST the authority and the

responsibility to establish standards for federal computer systems that

process sensitive but unclassified information after coordination with NSA.

These standards include acceptable methods to ensure the security and

privacy of information in those systems. In addition, NSA establishes

policies and procedures that must be used for the protection of classified

material. Both NIST and NSA have established procedures for the evaluation

and approval of cryptographic algorithms for use by the federal

government.

Although the RCAS contractor’s conceptual approach of condensing the

data to be signed and then encrypting the condensed value can produce

acceptable electronic signatures, the techniques adopted do not follow

federal government standards and practices which have been approved by

NIST and NSA. Our concerns include the use of (1) proprietary

cryptographic and hash algorithms which have not been approved by

Page 1 GAO/AFMD-93-70R RCAS Authentication
B-253174 

either NIST or NSA and (2) a cryptographic process that primarily depends

on the protection and secrecy of the cryptographic and hash algorithms.

We believe that several options are available to address our concerns.

Cryptographic and

Hash Algorithms

It is our understanding that the cryptographic and hash algorithms used in

your system were developed by your contractor and have not been

approved by either NIST or NSA. Since these agencies are recognized

experts on cryptographic algorithms, systems, and techniques for

unclassified and classified applications, respectively, we defer to them for

ensuring that the methodology selected is appropriate. The hash algorithm

appears to be critical to your signature generation process because it

represents a condensed version of the data which is used in that process.

Therefore, the hash algorithm needs to be designed so that it is

computationally infeasible to (1) find a message which corresponds to a

given message digest or (2) find two different messages which will

produce the same message digest. As in the case of cryptographic

algorithms, very few hash algorithms have maintained their integrity over

time.

Secrecy of

Cryptographic and

Hash Algorithms

As discussed in the material provided, the cryptographic and hash

algorithms appear to construct the keys used in their processes from the

data being signed. Since the algorithms are able to generate and derive the

critical keying material, any individual who has access to the algorithm

can derive the key. Once the key is known, the data can be changed and a

forged signature generated. When these altered data are validated later,

the forged signature will validate the changed data. We are concerned

about this approach because relying primarily on an algorithm’s secrecy

for its security increases the risk of accepting an improper signature as

valid. According to a NIST official, good cryptographic systems do not

depend entirely on the secrecy of the algorithm. Instead, they depend on

(1) using good key generation methods and (2) keeping the critical keying

material from unauthorized disclosure.

The unauthorized disclosure of your cryptographic algorithm would be

catastrophic to your electronic signature system. All data would become

suspect, and the electronic signature system would have to be

reengineered. During this reengineering process, other methods, probably

costly manual paper and handwritten signatures, would need to be

employed. We recognize that in good cryptographic systems the

unauthorized disclosure of critical keying material can also cause

Page 2 GAO/AFMD-93-70R RCAS Authentication
B-253174 

significant problems and may cause the existing data to become suspect.

However, the primary advantage of using sound cryptographic techniques

is that the system itself can still be used with new keying material.

Furthermore, the risk of unauthorized disclosure is increased in your

system because the electronic signature system is software-based and is

maintained in the RCAS system where access is more readily available than

if it resided in secure hardware-based cryptographic modules. For

example, one possible source of unauthorized disclosure would appear to

include the programmers working on the electronic signature generation

and validation modules.

Available Options Adopting and properly implementing government approved standards and

techniques would address our concerns. For example, proper

implementation of the proposed Digital Signature Standard (DSS) would be

acceptable for your unclassified data and NSA has agreed to accept it on a

case-by-case basis for classified applications. Therefore, NSA may also

approve its use in your system. Since your system processes classified

data, we would also accept a statement from NSA that your system has

adequate controls to ensure that the GAO criteria have been met.

Specifically, the signatures generated are to be (1) unique to the signer,

(2) under the signer’s sole control, and (3) capable of being verified. The

signatures must also be generated in a manner that links the data to the

signature. Therefore, should the underlying data change, the signature

would be invalidated during the signature verification process. We

recognize that other alternatives may also address our concerns.

We appreciate the opportunity to comment on your proposed electronic

signature approach and the challenges that your agency faces in

undertaking a major system development such as RCAS. We hope that our

comments will assist your efforts. Should you have any questions, please

contact Chris Martin, Assistant Director, at (202) 512-9481.

Sincerely yours,

Donald H. Chapin

Assistant Comptroller General

(901633) Page 3 GAO/AFMD-93-70R RCAS Authentication
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