NISTIR 7771
 

Conformance Test Architecture 

for Biometric Data Interchange 

Formats - Version Beta 2.0 

Fernando L. Podio 

Dylan Yaga 

Mark Jerde 
NISTIR 7771 

Conformance Test Architecture 

for Biometric Data Interchange 

Formats - Version Beta 2.0 

Fernando L. Podio 

Dylan Yaga 

Mark Jerde 

February 2011 

U.S. Department of Commerce 

Gary Locke, Secretary 

National Institute of Standards and Technology 

Patrick D. Gallagher, Director 
 

 

Reports on Computer Systems Technology 

The Information Technology Laboratory (ITL) at the National Institute of Standards and Technology 

(NIST) promotes the U.S. economy and public welfare by providing technical leadership for the Nation’s 

measurement and standards infrastructure. ITL develops tests, test methods, reference data, proof of 

concept implementations, and technical analysis to advance the development and productive use of 

information technology. ITL’s responsibilities include the development of technical, physical, 

administrative, and management standards and guidelines for the cost-effective security and privacy of 

sensitive unclassified information in Federal computer systems. This Interagency Report discusses ITL’s 

research, guidance, and outreach efforts in computer security, and its collaborative activities with 

industry, government, and academic organizations. 

National Institute of Standards and Technology Interagency Report 

37 pages (2011) 

Certain commercial entities, equipment, or materials may be identified in this 

document in order to describe an experimental procedure or concept adequately. 

Such identification is not intended to imply recommendation or endorsement by the 

National Institute of Standards and Technology, nor is it intended to imply that the 

entities, materials, or equipment are necessarily the best available for the purpose. 

iii 
 

Abstract 

The success of biometric applications is particularly dependent on the interoperability of biometric 

systems. Deploying these systems requires a comprehensive portfolio of biometric standards 

developed in support of interoperability and data interchange. A number of these domestic and 

international standards have been published and others are under development. The existence of 

these standards alone is not enough to demonstrate that products meet the technical requirements 

specified in the standards. Conformance testing captures the technical description of a specification 

and measures whether an implementation faithfully implements the specification. The Computer 

Security Division of NIST/ITL supports conformity assessment efforts through active technical 

participation in the development of conformance testing methodology standards and the development 

of associated conformance test architectures (CTA) and test suites (CTS). This NIST IR discusses 

the technological characteristics of the recently released CTA Beta 2.0. This architecture supports 

CTSs such as those designed to test implementations of biometric data interchange data formats. The 

information provided includes CTA module communication methods, key CTA features and highlevel sequence diagrams such as testing and decoding operations. It also addresses an introduction to 

testing binary data, structure testing by groups of fields and a discussion on test cases. Ongoing work 

on related tools development is also presented. 

Disclaimer 

Statements made in this paper should not be interpreted as standards, guidelines, best practices, or 

recommendations for specific changes to any other NIST publications. 

iv 
 

Table of Contents 

1 Introduction to Biometric Standards and Conformance Testing....................................1
 

1.1 Current Biometric Standard Development Activities in Support of Interoperability and 

Data Interchange....................................................................................................................... 1
 

1.2 Overview of Conformance Testing .................................................................................2
 

1.3 Previous and Current Development Work ......................................................................2
 

1.3.1 BioAPI Conformance Test Suite..............................................................................2
 

1.3.2 Conformance Test Architecture for Biometric Information Records - Beta 1.1 ........3
 

1.3.3 Advanced CTA for Biometric Data Interchange Formats and BIRs - Beta 2.0 ........3
 

1.3.4 Ongoing work ..........................................................................................................4
 

2 Technical Characteristics of NIST/ITL CSD CTA Beta 2.0................................................5
 

2.1 Introduction ..................................................................................................................... 5
 

2.2 High Level Architecture - GUI, Controller and CTS Modules..........................................5
 

2.3 GUI / Controller Communication Methods ......................................................................7
 

2.4 CTA Beta 2.0 Key Features ............................................................................................7
 

2.4.1 Dynamically-Loaded Modules .................................................................................7
 

2.4.2 Binary Data is in Context.........................................................................................7
 

2.4.3 Fields Belong to Groups ..........................................................................................7
 

2.4.4 Additional Data ........................................................................................................8
 

2.4.5 XML Manifests.........................................................................................................8
 

2.4.6 Decode ..................................................................................................................10
 

2.4.7 Test Cases ............................................................................................................10
 

2.4.8 Multiple Errors .......................................................................................................10
 

2.4.9 Approaches to Increase Confidence and Reliability ..............................................10
 

3 Introduction to Testing Binary Data .................................................................................12
 

3.1 Testing Binary Data – Manifest-Based .........................................................................12
 

3.2 Testing Binary Data - Decode-Based ...........................................................................12
 

3.3 Loading Binary Data into a Manifest .............................................................................12
 

3.4 Field-Based vs. Binary-Input-Only Testing ...................................................................14
 

3.4.1 Separate “Decode” Operation .....................................................................................14
 

3.4.2 Field-Length Testing ...................................................................................................14
 

4 Characteristics of NIST/ITL CSD CTA Local and Web Services Controllers ................15
 

4.1 Local Controller ............................................................................................................15
 

4.2 Web Services Controller ...............................................................................................15
 

4.3 Local and Web Services Controllers ............................................................................16
 

4.4 Multiple Web Services Controllers................................................................................16
 

4.5 Advantages and Disadvantages of the Web Services Architecture ..............................17
 

4.5.1 Advantages: ..........................................................................................................17
 

4.5.2 Disadvantages .......................................................................................................17
 

v 
 

Annex A- Structure Testing by Field Groups .........................................................................18
 

A.1 Testing of Groups of Fields ...............................................................................................18
 

A.1.1 Simple Finger Minutiae Format ..................................................................................18
 

A.1.2 Post Valid-Structure Processing.................................................................................20
 

Annex B. More About Test Cases ...........................................................................................22
 

B.1 Background....................................................................................................................... 22
 

B.2 Characteristics of the Test Cases Implemented in CTA Beta 2.0 .....................................23
 

Annex C - High Level Sequence Diagrams .............................................................................26
 

C.1 Initialization ...................................................................................................................... 26
 

C.2 Testing.............................................................................................................................. 26
 

C.3 Decoding...........................................................................................................................27
 

Annex D - More on Biometric Information Records ..............................................................29
 

Annex E- References ................................................................................................................ 30
 

List of Figures
 

Figure 2-1: NIST/ITL CTA............................................................................................................ 5
 

List of Tables
 

Figure 2-2: CTA High-Level Architecture ..................................................................................6
 

Figure 4-1: CTA’s Local Controller..........................................................................................15
 

Figure 4-2: CTA’s Web Services Controller............................................................................15
 

Figure 4-3: CTA’s Local and Web Services Controller Configuration .................................16
 

Figure 4-4: CTA’s Local and Web Services Controller Configuration .................................16
 

Figure C-1: Initialization Process ............................................................................................26
 

Figure C-2: The Testing Process.............................................................................................27
 

Figure C-3: The Decoding Process .........................................................................................28
 

Table 2-1: Binary data displayed in a hex editor ......................................................................9
 

Table 2-2: Binary data displayed in Altova’s XMLSpy® ..........................................................9
 

Table 2-3: Additional data included in the Manifest ................................................................9
 

Table 3-1: Initial Content of the Sample Manifest ..................................................................13
 

Table 3-2: Sample Manifest Showing Data Erased ................................................................13
 

Table 3-3: Input Binary Data Applied to the Sample Manifest ..............................................13
 

Table 3-4: Input Binary Data Longer Than Expected .............................................................13
 

Table 3-5: Input Binary Data Length Matches the Manifest’s Total expected Length ........14
 

Table A-1: Sample Manifest Showing Data Erased ...............................................................18
 

vi 
 

Table A-2: Sample Record Containing Three Finger Representations ................................ 18
 

Table A-3: Sample Record Showing an Error During MinX Values ...................................... 20
 

Table B-1 – Test Case Results ................................................................................................. 23
 

vii
 
 

 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

1 Introduction to Biometric Standards and Conformance Testing 

1.1 Current Biometric Standard Development Activities in Support of 

Interoperability and Data Interchange 

 One of the critical issues related to secured Information Technology (IT) systems and 

applications is the verification of the users’ identities. The relationship between a biometric 

characteristic (e.g., something that you are) and the users of a system or application provides 

a binding that is stronger than the binding that can be achieved between a user and other 

technologies that are currently in use for “personal authentication” such as passwords (e.g., 

something that you know) and tokens (e.g., something that you have). For decades, 

biometric technologies were used primarily in law enforcement applications. However, over 

the past several years the marketplace for biometrics solutions has significantly widened. 

Currently, they are increasingly being required in public and private sector applications 

worldwide to authenticate a person's identity, secure national borders and restrict access to 

secure sites including buildings and computer networks. 

The success of biometric applications is particularly dependent on the interoperability of 

biometric systems. Deploying these systems requires a comprehensive portfolio of biometric 

standards developed in support of interoperability and data interchange. In the U.S., the 

InterNational Committee for Information Technology Standards (INCITS) Technical 

Committee M1 – Biometrics was established with the purpose to ensure a high priority, 

focused, and comprehensive approach in the United States for the rapid development and 

approval of formal national and international biometric standards [1]. A number of American 

National Standards developed by INCITS M1 have been published [2]. They include 

biometric technical interface standards, data interchange formats, conformance and 

performance testing methodologies and biometric application profiles. 

NIST/ITL is responsible for the development of the ANSI/NIST ITL standard "Data Format 

for the Interchange of Fingerprint, Facial & Other Biometric Information". NIST/ITL (and 

its predecessor organizations) has been accredited by ANSI as a standards developer since 

October 5, 1984. NIST/ITL is accredited to develop voluntary consensus standards as a 

sponsor using the ANSI Canvass Method. This standard is used by law enforcement, 

intelligence, military, and homeland security organizations throughout the world. The 

current version of the ANSI/NIST-ITL standard is: Part 1 – (ANSI/NIST-ITL 1-2007) in 

Traditional Format and Part 2 – (ANSI/NIST-ITL 2-2008) in NIEM1

-conformant XML 

format [3]. 

ISO/IEC JTC 1/SC 37 - Biometrics was established in June 2002 and is responsible for the 

development of a large portfolio of international biometric standards in support of 

interoperability and data interchange. Currently the subcommittee’s membership includes 

twenty-eight national bodies, ten observer countries and a number of liaison organizations 

[4]. At the present time, the subcommittee is developing the “second generation” of 

1 NIEM, the National Information Exchange Model, is a partnership of the U.S. Department of Justice, the U.S. 

Department of Homeland Security, and the U.S. Department of Health and Human Services. It is designed to develop, 

disseminate and support enterprise-wide information exchange standards and processes that can enable jurisdictions to 

effectively share critical information in emergency situations, as well as support the day-to-day operations of agencies 

throughout the nation. 

1 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

biometric standards with the goal of improving the existing standards, adding functionality to 

the published standards and reflecting technology innovations and new customers’ needs. At 

the time of publication, forty-four international standards and six technical reports developed 

by the subcommittee have been published [5]. In addition to the type of standards developed 

by INCITS M1, ISO/IEC JTC 1/SC 37 is responsible for the development of biometric 

sample quality standards and standards and technical reports in support of cross jurisdictional 

issues related to the utilization of biometric technologies in commercial applications. The 

subcommittee is also developing a harmonized biometric vocabulary to serve the standards 

community as well as other customers. 

1.2 Overview of Conformance Testing 

The existence of base biometric standards alone (e.g., biometric data interchange standards, 

technical interface standards) is not enough to demonstrate that products meet the technical 

requirements specified in the standards. Conformance testing captures the technical 

description of a specification and measures whether an implementation faithfully implements 

the specification. INCITS M1 and JTC 1/SC 37 are responsible for the development of 

conformance testing methodology standards. At the present time, a number of these 

standards have been published and others are under development. They specify conformance 

testing methodology standards for biometric technical interfaces (e.g., BioAPI specification 

developed in INCITS M1 and JTC 1/SC 37) and biometric data interchange standard formats 

(e.g., 1st and 2nd generation of international biometric data interchange formats published or 

under development in JTC 1/SC 37). 

The Computer Security Division (CSD) of NIST/ITL supports the development of biometric 

conformance testing methodology standards and other conformity assessment efforts through 

active technical participation in the development of these standards and the development of 

associated conformance test architectures and test suites. NIST/ITL CSD develops these 

conformance test tools to support users that require conformance to selected biometric 

standards and to also support product developers interested in conforming to biometric 

standards by using the same testing tools available to users. These test tools support the 

possible establishment of conformity assessment programs to validate conformance to 

biometric standards. Conformance testing provides developers, users, and purchasers, with 

increased levels of confidence in product quality and increases the probability of successful 

interoperability. 

1.3 Previous and Current Development Work 

1.3.1 BioAPI Conformance Test Suite 

In 2006, NIST/ITL CSD released a BioAPI Conformance Test Suite (CTS) developed to test 

implementations of ANSI INCITS 358-2002, the BioAPI specification. This software tool 

was developed to help users verify the conformance of Biometric Service Providers to the 

BioAPI Specification 1.1 [6]. NIST/ITL CSD also co-sponsored with other members of 

INCITS M1 the development of a conformance testing methodology standard for BioAPI. 

This standard was published in 2008 as ANSI INCITS 429-2008, Information technology - 

Conformance Testing Methodology for ANSI INCITS 358-2002 BioAPI Specification. The 

BioAPI CTS implementation was developed using concepts and principles specified in the 

conformance testing methodology standard. This CTS was thoroughly tested with a number 

2 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

of commercially available vendor biometric subsystems for different modalities (e.g., face, 

iris and fingerprint recognition) claiming conformance to the BioAPI standard. The test 

results were successfully cross-validated with another similar CTS independently developed 

by DoD’s Biometric Task Force. The National Science and Technology Council 

Subcommittee on Biometrics and Identity Management listed the BioAPI CTS developments 

as one of the “Technology Successes” of 2006. 

1.3.2 Conformance Test Architecture for Biometric Information Records - Beta 

1.1 

In August 2008 NIST/ITL CSD released a conformance test architecture for Biometric 

Information Records and a Conformance Test Suite (CTS) for Patron Format A data 

structures specified in ANSI INCITS 398-2008, Information technology - Common 

Biometric Exchange Formats Framework [7]. The CTS for Patron Format A supported by 

this conformance testing architecture was developed to help users determine whether binary 

file implementations of Biometric Information Records (BIRs) based on this Patron Format 

conform to the standard. NIST/ITL CSD sponsored in INCITS M1 development of a 

conformance testing methodology standard for CBEFF (Common Biometric Exchange 

Format Framework) data structures specified in ANSI INCITS 398-2008 and submitted to 

INCITS M1 the test assertions and related test cases developed for the Patron Format A 

Conformance Test Suite as well as test assertions and test cases for other Patron Formats 

specified in the ANSI INCITS 398-2008 standard. 

1.3.3 Advanced CTA for Biometric Data Interchange Formats and BIRs - Beta 2.0 

CTA Beta 2.0, recently developed, supports CTSs designed to test implementations of 

biometric data interchange formats and the three components of BIRs conforming to CBEFF 

standards. As detailed below, CTA Beta 2.0 incorporates features designed to improve the 

confidence and reliability of test results and the usability of the test tools. Software 

development testing approaches incorporated in this CTA version allow for the potential of 

cleaner, more trustworthy code. In August 2010, this CTA was released with CTSs designed 

to test implementations of finger image and finger minutiae biometric data interchange 

formats specified in four American National Standards: 

− ANSI INCITS 378, American National Standard for Information technology – Finger 

Minutiae Format for Data Interchange (2004 and 2009 versions) 

− ANSI INCITS 381, American National Standard for Information technology - Finger 

− Image Based Interchange Format (2004 and 2009 versions) 

Downloads of CTA Beta 2.0 and the CTS, associated documentation, and sample data can be 

found in the download page [8] of the NIST Biometric Resource Center which is maintained 

by NIST/ITL Computer Security Division [9]. This NIST IR provides information on the 

technical characteristics of CTA Beta 2.0, including Graphical user Interface/Controller 

communication methods, key CTA features and high-level sequence diagrams. This NIST IR 

also addresses an introduction to testing binary data, structure testing by groups of fields and 

a discussion on test cases. 

3 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

1.3.4 Ongoing work 

Upgrades to the current version of the CTA are being made to improve usability and 

performance. Development of CTSs to test implementations of selected international 

standards (finger, face and iris image data formats) is underway. NIST/ITL CSD is also 

developing a CTS to test implementations of selected Record Types of ANSI/NIST ITL 1­

2007, Data Format for the Interchange of Fingerprint, Facial, & Other Biometric Information 

– Part 1” and started analysis of the existing draft for the 2011 version of the ANSI/NIST ITL 

standard [3]. 

4 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

2 Technical Characteristics of NIST/ITL CSD CTA Beta 2.0 

2.1 Introduction 

NIST/ITL CSD Beta 2.0 CTA supports CTSs designed to test implementations of biometric 

data interchange formats and any of the three components of Biometric Information Records 

(see Annex D). These CTSs determine whether data conforms to one or more 

implementations of standards or specifications. Typically, the user selects the data to be 

tested as well as the CTS designed to test implementations of the particular standard or 

specification, and then begins the testing process. Figure 2-1 depicts a conceptual 

representation of the CTA. The output of the selected CTS includes Graphical user Interface 

(GUI) indicators as well as user-selectable Logs in XML format and Reports developed in 

HTML format. 

Figure 2-1: NIST/ITL CTA 

2.2 High Level Architecture - GUI, Controller and CTS Modules 

As shown in Figure 2-2, the CTA architecture has three main components: the GUI, the 

Controller and the CTS Modules. 

The GUI is the component that interacts with the user to perform conformance testing. The 

Controller is the component between the GUI and the Testing Modules (CTSs) that accepts 

testing requests from the GUI, calls the specified modules with the required data, and returns 

the consolidated results from the Modules to the GUI. The Controller is more than a traffic 

cop between the GUI and the Modules. It performs high-level data testing such as: “Error: 

512 bytes expected but only 100 passed.” It also ensures all Field sub-arrays are initialized so 

that Modules are freed from null testing. 

CTSs are the components that test implementations of a standard or specification for 

conformance to that standard or specification (e.g., ANSI INCITS 378-2009 - Information 

Technology - Finger Minutiae Format for Data Interchange). As stated above, the CTA 

currently supports CTS Modules designed to test implementations of biometric data 

interchange formats as well as Modules to test implementations of each component of a 

Biometric Information Record (i.e., Standard Biometric Header (SBH), Biometric Data Block 

(BDB), and Security Block (SB)). 

5 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Figure 2-2: CTA High-Level Architecture 

The architecture design supports conformance testing performed against any single Module 

or any combination of Modules to test BIR components. As indicated by the Figure above 

there can be multiple biometric data interchange format Modules as well as BIR component 

Modules. The Controller discovers and loads the Modules at runtime using an “Add-in” or 

“Plug-in” architecture similar to many other programs. The primary benefits of the 

dynamically-loaded Module architecture are simplified development and distribution: 

−	 Simplified Development: The Modules are developed separately from the GUI and 

Controller. Significantly, no changes need to be made to the GUI or Controller to create 

a new Module or modify an existing Module. 

−	 Simplified Distribution: The GUI and Controller can be installed independently of any 

Modules, which means installing new or updated Modules can be as simple as copying 

the Module to a folder. 

The only requirement of a Module is that it be a .DLL that implements the IModule interface 

in the NIST_ITL.Modules namespace. The Modules are installed in the "Modules" 

subfolder. 

6 
 

 

 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

2.3 GUI / Controller Communication Methods 

The GUI and the Controller support two interfaces known as the Local Controller and the 

Web Service Controller. CTS Modules can be used on a local computer or they can be 

accessed on the Internet or an Intranet via Web Services. Advantages and disadvantages of 

the Web Service architecture versus the operation via the local controller are discussed in 

section 4. The recently released CTA Beta 2.0 supports only the local controller. The Web 

Services controller is under testing. 

2.4 CTA Beta 2.0 Key Features 

As discussed above, the CTA is a set of individual components that work together to perform 

conformance testing. Each component can be independently developed and tested. Users 

benefit from this approach since it allows for faster upgrades. Key features incorporated in 

the design of the architecture are discussed below. 

2.4.1 Dynamically-Loaded Modules 

The testing Modules are automatically loaded at runtime; they do not have to be “compiled 

into” or “linked into” the rest of the software. They can be developed and deployed without 

changing any other CTA software. A CTA user can simply download and install a new or 

upgraded testing Module without changing any other CTA software component. 

2.4.2 Binary Data is in Context 

When the CTA processes binary data, the first step is to place the data into an array of Field 

data structures. The primary benefit is that the users never have to interpret what the 27th (or 

10,027th) byte is; the CTA shows which Field the byte belongs to. A Module’s complexity is 

greatly reduced by the pre-parsed array of Fields. Fields are one of the keys that enable “Unit 

Testing for Data Formats Testing.” Section 2.4.9 introduces the reader to a brief discussion 

on Unit Testing. 

2.4.3 Fields Belong to Groups 

The CTS Modules implement testing of groups of fields. Annex A- Structure Testing by
 

Field Groups discusses this approach in detail and provides examples. 

These are three typical rules for the Record Header group of fields: 

− The Record Header must occur first. 

− The Record Header can occur only once. 

− The Record Header consists of these fields, in this order: 

− Format Identifier, Version, Record Length, ...
 

Processing of fields by groups enhances CTS Module confidence and reliability by reducing 

software complexity. These are the primary reasons:
 

− The CTS Modules call the same software library for group processing. The library has 

been thoroughly tested. No CTS Module has to create its own software for processing 

fields by groups. 

7 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

− Groups are defined in XML, not by hard-coded values typed by hand into a CTS Module. 

The XML format is far superior to hard-coded values for editing, proofreading, and 

transformation of the group information into other useful forms. 

− The part of the CTS Module that determines if the set of groups forms a valid data 

structure is very small and clear. 

− Once the structure has been determined valid, many level 2 assertions2

 become trivial to 

write and test. 

Additional information on this approach is discussed in Annex A. 

2.4.4 Additional Data 

The CTA supports optional auxiliary binary information called "Auxiliary Data". The 

purpose of Additional Data is to allow a field to pass that would normally fail under certain 

conditions. For example, some Modules are designed to test the content of the CBEFF 

Product Identifier field. Some standards state that CBEFF Product Identifier codes can be 

registered with the International Biometric Industry Association (IBIA) at www.ibia.org. 

The CTA Modules are released with a version of the codes from IBIA. During testing, if the 

CBEFF Product Identifier field has a code that is not on the list, the test fails. However, if the 

value matches exactly the value in Additional Data, the test passes. This allows tests to pass 

where the CBEFF Product Identifier code has not yet been registered, was registered after the 

release of the Module, or is strictly used for internal purposes and will not be registered. 

Additional Data is specified at the GUI level but acted upon at the Module level. The 

Module developer implements and documents the exact meaning of Additional Data for each 

field in which it is used. In existing Modules Additional Data is ignored for most fields and 

does not affect the processing at all. 

2.4.5 XML Manifests 

A Manifest defines the format to which a binary file conforms. It is saved in XML format. 

In testing, any number of binary files can be tested against a specific Manifest. When the 

format of a binary implementation of a standard is known in detail, the user provides the CTS 

that will be used to test the binary file(s) with information on the format via a Manifest. The 

CTA accepts Manifests in XML and provides the means for developing them. The Fields 

with all their information (Bytes, Lengths, Comments, etc.) can be saved in a Manifest. In 

addition to the Fields, the Manifest has additional information such as the Manifest’s Name, a 

Description, the Module(s) used, etc. The Manifests can be easily shared and displayed. 

Since a Manifest defines a format, binary data is more easily analyzed and understood. Table 

2-1 depicts binary data displayed in a hex editor. 

2 In Level 1 testing, an implementation is checked field‐by‐field, for conformance with the specification of the 

standard, both in terms of ranges, character types, encoding and cardinality. In Level 2 testing, an implementation is 

checked to determine if it is internally consistent. This is achieved by relating values from one or more fields or 

information items within an implementation to other values within the same implementation. Level 2 tests require more 

complex testing than Level 1, usually after the entire implementation has been parsed. 

8 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Table 2-1: Binary data displayed in a hex editor 

Table 2-2 shows a screenshot of the same data, saved in a Manifest and displayed in Altova’s 

XMLSpy®. The binary data, shown in the last column, is associated with a Field Name, 

shown in the “= Name” column. 

Table 2-2: Binary data displayed in Altova’s XMLSpy® 

Table 2-3 shows additional data shown in the XMLSpy® screenshot, this additional 

information included in the Manifest is useful too. Note that the exact versions of the 

Modules that created the Manifest are saved in the Manifest. 

Table 2-3: Additional data included in the Manifest 

9 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

2.4.6 Decode 

When the structure of a binary implementation of a standard is not known, a Manifest to 

describe the binary input to the CTS cannot be developed. In this case, Manifest-Based 

testing cannot be performed. The CTS develops the related Manifest based on decoding the 

input binary file. This is called Decode-Based binary testing. The structure of the data is 

determined as the input bytes are processed; there is no external template, schema or 

Manifest that describes the structure. 

2.4.7 Test Cases 

A CTA Test Case encapsulates both the data for and the expected results of a testing 

operation. When saved the Test Case is stored in XML format. A Test Case can test, for 

example, “This list of 10 fields should have these 4 specific errors.” When the Test Case is 

tested, if 4 errors are found, and they exactly match the 4 expected errors, the GUI indicates 

the Test Case succeeded. 

“I am expecting to find these 4 errors. These same 4 errors were found during testing. Since 

I found what I was looking for, proof that the Module finds the errors it should, the Test Case 

passes.” 

Well designed Test Cases are a critical tool to test the reliability of a CTS. They are 

primarily used by CTS Module developers. A CTA/CTS user may never need to use a Test 

Case. Test Cases are very similar to Manifests; the chief difference between them is their 

purpose. Generally speaking, CTA/CTS users use Manifests to perform data testing, whereas 

CTS Module developers use Test Cases to ensure the correct operation of their Modules. 

Manifests and Test Cases contain the format specification of binary data in a convenient form 

for storage, sharing and analysis. For testing, their data is converted by the GUI into the 

array of Fields and supporting information that is passed to the Controller. When testing is 

complete the results are stored in the Manifest or Test Case. Depending on the specific GUI 

operation, the updated Manifest or Test Case can optionally be saved. 

To reduce CTS software complexity, Manifests and Test Cases have an identical format. In 

fact, a Manifest is just a “Complete” Test Case that expects to “Pass.” For the convenience 

of CTA/CTS users, the GUI defaults to working with Manifests and Test Cases are different 

at the GUI and documentation level, but they have the same XML structure. A more detailed 

discussion on Test Cases can be found in Annex B. 

2.4.8 Multiple Errors 

To minimize users’ time and work in correcting problems, the CTA supports Modules 

returning multiple errors from a single test. 

2.4.9 Approaches to Increase Confidence and Reliability 

To trust a software program, it is not enough to know that the software returns good results 

when presented with good data. The Module developer and the user also need to know that 

the software behaves as expected when it is presented with erroneous data. Perhaps the 

single greatest improvement in software reliability in the past 30 years has come from the use 

of Unit Testing. These tests verify the correct operation of the product under both good and 

bad conditions. When a bug is discovered it is common practice to first write a unit test that 

10
 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

duplicates the error, then fix the error, and then add the updated unit test to the product’s 

suite of tests to ensure the bug never occurs again. By using both good software development 

methods and the Beta 2.0 CTA’s Test Case capability, the software developers have a great 

deal of confidence that the Modules they create will respond appropriately to both good and 

bad data. The Beta 2.0 CTA brings Unit Testing to data formats testing. 

11
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

3 Introduction to Testing Binary Data 

As stated in section 2, testing binary data can be performed using a Manifest that describes 

the format of the binary data or by decoding the binary data. 

3.1 Testing Binary Data – Manifest-Based 

In this common GUI operation a user elects to test one or more binary files with one 

Manifest. The online help tool or the Users' Guide that can be downloaded from the 

NIST/ITL CTA Beta 2.0 release web page [8] provides detailed information on how to 

perform binary testing. The process within the GUI is as follows: 

1. The Manifest is loaded in memory. 

2. The binary file is loaded into the Manifest as illustrated in section 3.3. 

3. The Manifest is passed to the Controller for Testing. See the High Level Sequence 

Diagrams in Annex C. 

4. When the results are received back from the Controller, the GUI is updated. If 

selected by the user, the results are added to the Log and/or Report. 

5. If there are more binary files, the process continues with step 2. If there are no more 

binary files the operation is complete. 

3.2 Testing Binary Data - Decode-Based 

This common GUI operation is very similar to the Manifest-Based Binary Data Testing 

process discussed above. The difference is that each binary file creates its own Manifest. 

These are the steps: 

1. The binary file is loaded into memory and passed to the Controller for Decoding. See 

the High Level Sequence diagrams in Annex C. 

2. The Controller returns the array of Field data structures created by the CTS Module 

"Decode" operation. 

3. The array of fields is passed back to the Controller for Testing. 

4. When the test results are received back from the Controller the GUI is updated. If 

selected by the user, the results are added to the Log and/or Report. 

5. If there are more binary files, the process continues with step 1. If there are no more 

binary files, the operation is complete. 

3.3 Loading Binary Data into a Manifest 

Loading binary data into a Manifest happens frequently in GUI operations. These are the 

steps: 

1. The Manifest is loaded into memory. For simplicity, the sample Manifest shown in Table 

3-1 below has three fields and a total of six expected bytes. The Manifest initially looks like 

this. 

12
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Table 3-1: Initial Content of the Sample Manifest 

2. Next, the Manifest’s data is erased. The cells highlighted in Table 3-2 (Actual Length) 

indicate length errors that would be identified by Testing. 

Table 3-2: Sample Manifest Showing Data Erased 

3. Next, as shown in Table 3-3, the input binary data is applied to the memory Manifest, 

filling each field completely with bytes before going to the next field. If there are too few 

bytes, one or more fields are not filled to capacity. 

Table 3-3: Input Binary Data Applied to the Sample Manifest 

As shown in Table 3-4, if the binary input is longer than expected, the excess data is in the 

last field and the actual field length is highlighted in yellow. 

Table 3-4: Input Binary Data Longer Than Expected 

When the length of the binary input data exactly matches the Manifest’s total expected 

length, each field has the expected number of bytes as shown in Table 3-5 below. 

13
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Table 3-5: Input Binary Data Length Matches the Manifest’s Total expected Length 

The memory-Manifest is loaded with new binary data, ready for the next part of the GUI 

operation. 

3.4 Field-Based vs. Binary-Input-Only Testing 

The Fields data structure and its persistence as an XML Manifest bring a high level of 

understanding and documentation to binary data. This organization of binary data means the 

CTA operates somewhat differently from a binary-data-only testing approach where data 

input is just an array of bytes. 

3.4.1 Separate “Decode” Operation 

In binary-input-only testing, the structure of the data is determined as the input bytes are 

processed; there is no external template, schema or Manifest that describes the structure. In 

the CTA, with its Fields data structure architecture, determining the structure is called 

Decoding and it is a separate operation from Testing. (Decoding is discussed in section 

2.4.6.) Most of the time when Decode is called in user testing, it is immediately followed by 

a Testing call. 

3.4.2 Field-Length Testing 

During binary-input-only testing, if the first field is two bytes long, the first two bytes of the 

input are the first field’s data. There is no other interpretation. 

In Field-Based testing, the first field is a Field data structure. It has Length and Data 

components. In the CTA, each Field’s Length is verified. There is no analogous concept in 

binary-input-only testing. This is not as inconvenient as it may sound because of the 

intelligence built into the GUI. For example, users cannot change the length of a fixed-length 

field. 

14
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

4 Characteristics of NIST/ITL CSD CTA Local and Web Services 

Controllers 

4.1 Local Controller 

Figure 4-1 depicts a graph of the Local Controller interface. In this configuration the GUI, 

Controller and Modules are all on the same computer and communicate in the simplest, 

fastest method. 

Figure 4-1: CTA’s Local Controller 

4.2 Web Services Controller 

The recently released CTA Beta 2.0 supports only the local controller. The Web Services 

controller is under testing. Figure 4-2 shows the Web Services Controller configuration. In 

this configuration, the GUI and Controller use the Simple Object Access Protocol (SOAP) 

standard to exchange data. This has more overhead than Local Controller communication, 

but little difference in speed was noted during initial testing when the Web Services 

Controller was installed on the same PC as the GUI. 

Figure 4-2: CTA’s Web Services Controller 

15
 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Not all operating systems support self-hosting of web services. For example, a Web Services 

Controller can be installed and run on Microsoft® Windows XP Professional, but not on 

Microsoft® Windows XP Home. 

4.3 Local and Web Services Controllers 

As shown in Figure 4-3, the GUI can be configured to support both communication methods, 

but only one can be active at a time. 

Figure 4-3: CTA’s Local and Web Services Controller Configuration 

4.4 Multiple Web Services Controllers 

Finally, since Web Services are specified by a Uniform Resource Identifier (URI), similar to 

a URL, the GUI that supports the Web Services Controller can connect to many different 

Web Services Controllers, one at a time. 

Figure 4-4: CTA’s Local and Web Services Controller Configuration 

16
 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

4.5 Advantages and Disadvantages of the Web Services Architecture 

4.5.1 Advantages: 

There are three key advantages to implementing and using a Web Services architecture 

instead of using a local controller: 

•	 Simple PC Configuration and Maintenance: Only the GUI needs to be installed on a 

user’s PC. An organization can be responsible for maintaining the server(s) which have 

the Controller and Modules. In this architecture, upgrading every user to a new version 

of a specific Module is just a matter of updating the server, not each individual PC. 

•	 Testing Flexibility: Since the GUI can connect with many different Web Services 

Controllers, specific Web Services Controllers can be established for different
 

purposes. For example, Module developers may establish several Web Services 

Controllers that demonstrate the capabilities of their Module at various points in its 

development. 

•	 Enhanced Intellectual Property (IP) Protection: If an organization develops a 

Module that contains IP, they may not wish to release the Module for installation on 

PCs, as there is little or no protection against a sufficiently-motivated individual 

disassembling their Module. If they make the Module available only from a Web 

Services Controller installed on their own secure server(s), the IP is much better 

protected. 

4.5.2 Disadvantages 

•	 Connectivity: If the Web Services Controller is located on a separate machine from 

the GUI, a network connection is required between the GUI computer and the Web 

Services Controller computer. 

•	 Potentially Slower Testing: In NIST/ITL CSD's initial testing there was a negligible 

speed difference between the Local Controller configuration and the Web Services 

Controller configuration when the Web Service Controller was installed on the same 

computer as the GUI. Network conditions and Internet speed will be factors in 

execution speed. 

17
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Annex A- Structure Testing by Field Groups 

A.1 Testing of Groups of Fields 

The CTS Modules implement testing of groups of fields. Examples of these groups in 

biometric data interchange formats include a Record Header and a Finger View Header or a 

General Header and a Finger Minutiae Header (Finger Header). Processing of fields by 

groups reduces complexity. The main reasons for using this approach were detailed in CTA 

Beta 2.0 Key Features in Subsection 2.4.3. To better illustrate this concept, a simple finger 

minutiae standard and its field groups is described. Though the format is fictional, it 

highlights key points of actual standards and testing of their implementations with CTS 

Modules. 

A.1.1 Simple Finger Minutiae Format 

A simple finger minutiae standards' structure is a Record Header followed by one or more 

Finger Records. A Finger Record consists of a Finger Header followed by zero or more sets 

of (X, Y) Minutiae Points that make up a Minutiae Data Group. Table A-1 shows the field 

names, their abbreviations, and the group to which they belong. 

Table A-1: Sample Manifest Showing Data Erased 

As shown in Table A-2, this is a sample record of three fingers with three, one and two 

Minutiae Point pairs each. Fields that are not important for this discussion are blank. 

Table A-2: Sample Record Containing Three Finger Representations 

18
 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

The higher level of abstraction of groups vs. fields has the potential for cleaner, more 

trustworthy code. Using table-driven logic, the software to test the record should begin with 

the Record Header. This is much simpler than field-by-field testing: 

The first field should be the Format Identifier. 

 The next field should be the Version. 

 The next field should be ... 

This is especially true when the number of fields in a group, say the Minutiae Data group, 

varies based on a value in a header field. Some groups could have just (X, Y) sets but others 

may also have angle and quality information. In real-world Modules, some groups may have 

two fields and others five in different parts of the record. 

The pseudo code below is for testing the Sample format record using Field Groups. 

Check RecordHeader, Exit if bad 

Read NumberOfFingers 

ForEach NumberOfFingers 

{ 

Check FingerHeader, Exit if bad 

Read NumberOfMinutiae 

ForEach NumberOfMinutiae 

Check MinutiaeDataGroup, Exit if bad 

} 

19
 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Flag any remaining fields as Unexpected. 

The same structure testing can be done using just the fields, but many more lines of code are 

needed. 

A.1.2 Post Valid-Structure Processing 

An exciting consequence of separate structure testing is that many other tests become easy to 

do as a separate pass once the structure is known to be good. Consider testing that every 

MinX is in range of its SizeX value. If the record structure is known to be good then there 

are no “orphan MinX” fields; each MinX field “belongs” to a Finger Header that has the 

SizeX field that applies to the MinX field. The algorithm for SizeX/MinX testing then 

becomes very simple as illustrated by this pseudo code. 

ForEach Field 

{ 

If Field is SizeX

 Read ValueSizeX 

If Field is MinX 

{ 

 Read ValueMinX 

If ValueMinX >= ValueSizeX 

 Indicate Error 

} 

} 

In the following example a MinX value of 125 occurs twice. The first occurrence is an error 

because it is larger than its corresponding SizeX value. The second occurrence is valid. 

Table A-3: Sample Record Showing an Error During MinX Values 

20
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

This is a very simple, made-up format with limited example potential. The principle is valid. 

In real-world Modules, there are tests that are much easier to perform if the record’s structure 

is known to be good. 

21
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Annex B. More About Test Cases 

B.1 Background 

CTA Beta 2.0 introduces new, more powerful Test Case features that allow more testing with 

less effort. This Annex provides information primarily for Module Developers, but it is 

included in this document because some CTA users may find that the information helps them 

understand the CTA and associated Conformance Test Suites better. 

Perhaps a made-up scenario will make this section as short and clear as possible. Suppose a 

Module is being written for a standard that has this text: 

The name of the second field shall be “Foo”. It shall be two bytes long and shall have the 

value 3 (0x 00 03). 

Ideally, all possible values should be tested, but realistically that cannot be done for nontrivial test Modules. One quickly encounters the “More tests are needed than electrons in the 

universe” combinatorial condition where the required testing time is measured in geologic 

eras. 

Choosing test values is therefore somewhat of an art in which choosing “values likely to fail” 

is very important. The following are the required Foo value tests, the minimal set of tests 

necessary to gain confidence that the Module is very likely to handle Foo values properly: 

1. Three (3). The expected value must pass. 

2. Two (2) and four (4). It is important to test values just outside of the range of valid values 

to make sure they fail. 

3. No-bits and all-bits (0x 00 00 and 0x FF FF). Boundaries, the edge conditions that 

overflow, underflow and signed-vs-unsigned considerations potentially raise havoc. 

Boundary-bits values should fail. 

The 5 test values (3, 2, 4, 0x 00 00 and 0x FF FF) are sufficient to test this feature, provided 

that a competent programmer wrote software that is intended to work. Additional strategies 

are needed to protect against malicious code. 

Therefore, a minimum of five values should be tested in this example: 3, 2, 4, 0x 00 00 and 

0x FF FF. Only one value (3) should pass and the rest should fail. Prior to CTA Beta 2.0, 

these five test values required five different, complete Test Cases. They could not be 

combined in a single Test Case because they required a complete record. Over time the 

following problems were noted. 

1. Developing Test Cases was a slow process. Each Test Case had to pass all the Module’s 

tests with the exception of the specific error desired (e.g., having all fields passed but 

Format ID would be a failing Test Case for Format ID). Therefore, each Test Case was 

essentially a complete record, with at least the minimum number of fields. 

2. Test Case maintenance was an issue. Each Test Case had to pass all Module tests or allbut-one test if it was testing for failure. Since the Module and its Test Cases were 

developed side by side as the project progressed, it was fairly common for a new test in the 

Module to break a number of existing Test Cases. 

22
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

3. Test Cases were obscure. Since the one field in error was just another field in a list of 20, 

30 or 50 fields, it did not stand out in any way. The purpose of the Test Case could not be 

determined by superficial examination. 

4. At one point there were so many Test Cases developed for a Module that they had to be 

put in separate folders because the standard Windows® “Open File” dialog box, in 

Microsoft® Windows® XP Professional, could not open all of them at the same time. 

5. There were so many Test Cases that there was a “Cannot see the forest for the trees” 

problem. It was hard to look at the list of Test Cases and determine “Test Coverage”, that 

is, whether or not the existing Test Cases tested every desired test scenario. 

B.2 Characteristics of the Test Cases Implemented in CTA Beta 2.0 

The Modules supported by the previous CTA version were “internally modular.” That is, the 

code that tested that Foo=3 was separate from the code that checked that Foo was the 2nd 

field, which was itself separate from code that made sure the Foo field only occurred once. 

Different parts of the code tested different characteristics of the data. Test Cases had always 

run all tests in the module, but changes could be made to allow the Module to run only some 

of its tests, and to allow the passing of a “flag value” to the Module to determine which code 

paths to run and which tests to perform. 

In this CTA version, each module has associated Test Cases that "prove" that they work with 

a wide variety of data. The Test Cases allowed the developers to, if you will, “hammer loud 

and long” on the code, thoroughly chasing away all bugs. If and when more bugs were 

found, one or more Test Cases were created to show they have been fixed. These errors were 

not expected to reappear since all Test Cases were run before a Module was released. 

Continuing the Foo scenario, it is suggested that Module developers support the “Data Only” 

type of Test Case testing, and implement Modules in such as way as to only call the valuetesting parts of the code. In “Data Only” testing the code that makes sure Foo is the second 

field or the code that makes sure Foo occurs but once are not addressed in the Test Case (this 

tests data only without testing the relationship between fields and the structure). These are 

tested under testing types such as “Complete”, “Structure”, or “Partial”. Just fields’ data 

values are tested and all the structural considerations are ignored. As shown in Table B-1, 

doing this allows a single Test Case to test all five values discussed above. 

Table B-1 – Test Case Results 

Test 

Number 

Field 

Name Value 

Expected 

Test 

Result 

1 Foo 3 Pass 

2 Foo 2 Fail 

3 Foo 4 Fail 

23
 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Test 

Number 

Field 

Name Value 

Expected 

Test 

Result 

4 Foo 0x 00 00 Fail 

5 Foo 0x FF FF Fail 

When the Module returns these results, the developer can save this Test Case so that it 

“Passes” whenever it is tested and the Module returns these exact errors. The Test Case can 

be run anytime during the Module’s lifetime to ensure Foo’s value is handled correctly by the 

Module. 

A real worth of Test Case Types is in limiting the Errors returned to those of interest. 

It is suggested that Module developers adopt a Test Case naming convention that conveys 

maximum understanding by simply looking at the Test Case names. Below is a partial list of 

the Test Cases developed for a NIST/ITL CTS Module. Though there are fewer than 100 

Test Cases, confidence is high that the Module performs as expected. 

L1-02-PassFail-Format Identifier.xml3
 

L1-02-PassFail-Version.xml 

L1-03-L2-PassFail-Record Length.xml

L1-04-PassFail-CBEFF PID Owner.xml 

L1-05-Pass-CBEFF PID Type.xml

L1-06-07-Pass-CaptureEquipment.xml

L1-08-Pass-ImageSizeX.xml

L1-09-Pass-ImageSizeY.xml 

... 

L1-42-PassFail-Delta Angle 1.xml

L1-43-PassFail-Delta Angle 2.xml

L1-44-PassFail-Delta Angle 3.xml 

L2-CoreDelta-01 Fail No XData Area.xml 

L2-CoreDelta-02 Fail Not XDAType.xml

L2-CoreDelta-03 Fail XDAType Not CoreDelta.xml

L2-CoreDelta-04 Fail Not CoreInfType_Num.xml 

... 

L2-RidgeCount-01 Fail No XData Area.xml

L2-RidgeCount-02 Fail Not XDAType.xml

L2-RidgeCount-03 Fail Not RidgeCount.xml

L2-RidgeCount-04 Fail Missing XDAL.xml 

... 

L2-XDLen 04 - Orphan XDAL.xml

L2-XDLen 05 - Len Err.xml 

L2-XDLen 06 - Pass Multiple XDALs.xml

L2-XDLen 07 - Zero len XDAL Passes.xml 

L2-XDLen 08 - Zero len XDAL Orphan.xml 

3

 PassFail” represents a mixture of passes and fails. 

24
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Level 1 tests are named, “L1 - FieldNumber(s) – Results – FieldName”. 

Level 2 tests are named, “L2 - FieldsGroup – Counter Other-Information.” 

The Test Case “L1-03-L2-PassFail-Record Length.xml” is an exception. It is both possible 

and desirable for the field Record Length to perform both Level 1 testing (“Is the value in the 

allowable range?”) and Level 2 testing (“Does the value match the number of bytes read?”) at 

the same time in the same block of code. The Test Case name, therefore, reflects both L1 

and L2 testing. 

In summary, CTA Beta 2.0’s Test Cases provide an excellent mechanism for thoroughly 

testing CTS Modules. 

25
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Annex C - High Level Sequence Diagrams 

Three operations involve all the CTA components. They are initialization, testing and 

decoding. 

C.1 Initialization 

The diagram in Figure C-1 illustrates the initialization process. 

Figure C-1: Initialization Process 

Note: "4" and "5" are the same as "2" and "3". 

The GUI initializes the Controller, expecting to receive information about all available 

Modules. The controller loads each Module it finds, receiving from each Module the 

Module’s type, its fields and the list of errors it can find as part of its testing. The Controller 

consolidates this information, returning to the GUI a list of all loaded Modules, their fields 

and their errors. 

C.2 Testing 

The diagram in Figure C-2 illustrates the testing process. This is the “behind the scenes” 

process called by a number of separate GUI operations: testing binary files with a Manifest, 

testing a Manifest or Test Case individually on the “Builder Tab”, and testing a number of 

Test Cases at the same time. 

The Controller gets the request from the GUI and calls up to three modules (i.e., SBH, BDB 

SB). See Annex D, More on Biometric Information Records. The Controller gets the list of 

26
 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

errors from each module, consolidates the errors into a single Error List and returns it to the 

GUI. When the GUI receives the results, it interprets the Error List and informs the user. 

For example, an Error List with four items would indicate failure of a Manifest + Binary File 

test, but it could be a success if the test was a Test Case and the four errors matched the 

expected errors. 

Figure C-2: The Testing Process 

C.3 Decoding 

As stated above, Decoding refers to an analysis operation performed by a Module. The input 

is binary (an array of bytes) and the output is an array of Fields that correspond to the binary 

input. 

In most GUI operations the Decode operation is immediately followed by a Test operation, 

without any further user intervention. Put another way, to Decode a binary file is to develop 

or discover its structure. 

The diagram in Figure C-3 illustrates the decoding process. The GUI sends the Controller an 

array of bytes. The Controller calls the proper Module, passing it the array of bytes. (CTA 

Beta 2.0 calls one Module as part of a Decode operation.) The Module passes back to the 

controller the array of Fields as determined by specific values in the byte array. The 

Controller returns the array of Fields to the GUI. For most operations in the GUI, the GUI 

immediately calls the Controller to perform a Test operation on that same array of Fields. 

27
 
 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Figure C-3: The Decoding Process 

28
 
 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Annex D - More on Biometric Information Records 

The Common Biometric Exchange Formats Framework (CBEFF) standards describe a set of 

data elements and values to support biometric data records in a common way. These data 

elements can be encoded in a record header that facilitates exchange of biometric data 

between different system components or between systems. The CBEFF standards provide 

forward compatibility for technology improvements and allow creation of new patron 

formats (instantiations of CBEFF). The BIR structure defined by CBEFF supports security 

(digital signatures and data encryption), processing information and descriptive attributes of 

the biometric data. 

The CBEFF record defines three components in a single structure: 

1.The SBH (Standard Biometric Header) includes the data elements (required and 

optional) that describe the biometric data's structure and selected attributes (metadata) 

of its content. These include the appropriate standardized data elements and values 

defined by CBEFF, and may also include data elements and values defined by a 

patron format specification to satisfy unique requirements. 

2.The BDB (Biometric Data Block) contains the biometric data. It can contain processed 

or unprocessed data. A BDB typically conforms to a standardized data interchange 

format such as the formats developed by INCITS M1 [2] or JTC 1/SC 37 [5] but 

could – alternatively – contain a proprietary data structure. Fields in the SBH 

specifically identify the BDB format and other metadata so the biometric application 

can pass the BIR or the BDB content to the correct biometric processing module. 

3.The SB (Security Block) can contain a digital signature, message authentication code 

(MAC), or algorithm identifier information and parameters required for applying 

integrity and encryption processes to the BDB. CBEFF requires that the SBH not be 

encrypted, although it can be covered by integrity algorithms. As with the BDB 

format, the SB format is defined by an SB "owner" and can be adapted to the specific 

requirements of an application or system. Fields in the SBH identify the SB format 

to guide integrity checking of the entire BIR and to support appropriate decryption of 

the BDB. 

As discussed in the introduction, CTA Beta 2.0 supports CTSs to test implementations of 

biometric data interchange data formats as well as implementations of the three components 

of CBEFF Biometric Information Records (BIRs). 

29
 
 

 

 

 

 

NISTIR 7771 - Conformance Test Architecture for Biometric Data Interchange Formats - Version Beta 2.0 

Annex E- References 

[1] INCITS M1 – Biometrics Public Homepage - 

http://standards.incits.org/a/public/group/m1 

[2] Published Biometric American National Standards Developed by INCITS M1 as of 

September 2010 - 

http://www.incits.org/tc_home/National_Standards_Published_as_of_09_08_2010.pdf 

[3]	 ANSI/NIST-ITL Standards Homepage – 

http://www.nist.gov/itl/iad/ig/ansi_standard.cfm 

[4] ISO/IEC JTC1/SC 37 – Biometrics Public Homepage - 

http://www.iso.org/iso/jtc1_sc37_home 

[5] Published Biometric International Standards Developed by ISO/IEC JTC 1/SC 37 – 

Biometrics as of September 2010 - 

http://www.incits.org/tc_home/International_Standards_Published_as_of_09_08_2010.p 

df 

[6]	 BioAPI Conformance Test Suite and associated documentation download - 

http://www.itl.nist.gov/div893/biometrics/BioAPI_CTS/index.htm. 

 [7] Conformance Test Architecture for Biometric Information Records and CBEFF Patron 

Format A Conformance Test Suite - 

http://www.itl.nist.gov/div893/biometrics/CBEFF_PFA_CTS/index.htm. 

[8] NIST/ITL Conformance Test Architecture (CTA) and Test Suites (CTSs) for Biometric 

Data Interchange Formats and Biometric Information Records Beta Implementation 

V2.0 Homepage - http://www.nist.gov/itl/csd/biometrics/biocta_download.cfm 

[9] NIST’s Biometric Resource Center: http://www.nist.gov/itl/csd/biometrics/ 

30