This work is on biometric data indexing for large-scale identification systems with a focus on different biometrics data indexing methods. It provides state-of-the-art coverage including different biometric traits, together with the pros and cons for each. Discussion of different multimodal fusion strategies are also included.

Preface i

Contents iii

List of Figures ix

List of Tables xix

1 Fundamentals of Biometric Technology 1

1.1 Biometric Authentication Technology 1

1.2 Some Major Biometric Applications 2

1.3 Operational Process of Biometric Technology 4

1.4 Biometric Data Indexing 7

1.5 Metrics for Performance Measure 7

1.6 Biometric Modalities 8

      1.6.1 Iris Biometric 9

      1.6.2 Fingerprint Biometric 9

      1.6.3 Face Biometric 9

      1.6.4 Palmprint Biometric 10

      1.6.5 Hand Geometry Biometric 10

      1.6.6 Voice Biometric 11

      1.6.7 Gait Biometric 12

      1.6.8 Signature Biometric 12

1.7 Comparative Study of Different Biometric Modalities 13

      1.7.1 Identification of Parameters 13

      1.7.2 Estimation of Values of Parameters 14

      1.7.3 Estimation of Impact Value 15

      1.7.4 Quantitative Comparison 21

1.8 Summary 21

2 Multimodal Biometric and Fusion Technology 33

2.1 Multimodal Biometric Authentication Technology 33

2.2 Fusion of Multimodalities 34

2.3 Fusion Levels 36

      2.3.1 Sensor Level Fusion 36

      2.3.2 Feature Level Fusion 38

      2.3.3 Match-score Level Fusion 40

      2.3.4 Decision Level Fusion 41

2.4 Different Fusion Rules 42

      2.4.1 Fixed fusion rules 42

      2.4.2 Trained Fusion Rules 45

2.5 Comparative Study of Fusion Rule 62

2.6 Summary 68

3 Biometric Indexing: State-of-the-Art 79

3.1 Survey on Iris Biometric Data Indexing 79

      3.1.1 Iris Texture-Based Indexing 80

      3.1.2 Iris Color-Based Indexing 82

3.2 Survey on Fingerprint Biometric Data Indexing 83

      3.2.1 Minutiae-Based Indexing 85

      3.2.2 Ridge Orientation-Based Indexing 88

      3.2.3 Other Feature-Based Indexing Techniques 92

3.3 Survey on Face Biometric Data Indexing 94

3.4 Survey on Multimodal Biometric Data Indexing 95

3.5 Summary 97

4 Iris Biometric Data Indexing 111

4.1 Preliminaries of Gabor Filter 112

4.2 Preprocessing 115

4.3 Feature Extraction 117

4.4 Index Key Generation 118

4.5 Storing 119

      4.5.1 Index Space Creation 119

      4.5.2 Storing Iris Data 120

4.6 Retrieving 124

4.7 Performance Evaluation 127

      4.7.1 Performance Metrics 128

      4.7.2 Databases 130

      4.7.3 Evaluation Setup 131

      4.7.4 Validation of the Parameter Values 132

      4.7.5 Evaluation 134

4.8 Comparison with Existing Work 141

4.9 Summary 143

5 Fingerprint Biometric Data Indexing 149

5.1 Preprocessing 150

      5.1.1 Normalization 150

      5.1.2 Segmentation 151

      5.1.3 Local Orientation Estimation 152

      5.1.4 Local Frequency Image Representation 152

      5.1.5 Ridge Filtering 153

      5.1.6 Binarization and Thinning 154

      5.1.7 Minutiae Point Extraction 154

5.2 Feature Extraction 157

      5.2.1 Two Closest Points Triangulation 157

      5.2.2 Triplet Generation 158

5.3 Index Key Generation 160

5.4 Storing 163

      5.4.1 Linear Index Space 164

      5.4.2 Clustered Index Space 165

      5.4.3 Clustered kd-tree Index Space 168

5.5 Retrieving 173

      5.5.1 Linear Search (LS) 174

      5.5.2 Clustered Search (CS) 175

      5.5.3 Clustered kd-tree Search (CKS) 177

5.6 Performance Evaluation 178

      5.6.1 Databases 178

      5.6.2 Evaluation Setup 181

      5.6.3 Evaluation 182

      5.6.4 Searching Time 192

      5.6.5 Memory Requirements 195

5.7 Comparison with Existing Work 195

5.8 Summary 199

6 Face Biometric Data Indexing 205

6.1 Preprocessing 206

      6.1.1 Geometric Normalization 206

      6.1.2 Face Masking 208

      6.1.3 Intensity Enhancement 209

6.2 Feature Extraction 210

      6.2.1 Key Point Detection 211

      6.2.2 Orientation Assignment 215

      6.2.3 Key Point Descriptor Extraction 217

6.3 Index Key Generation 218

6.4 Storing 220

      6.4.1 Index Space Creation 220

      6.4.2 Linear Storing Structure 223

      6.4.3 Kd-tree Storing Structure 223

6.5 Retrieving 225

      6.5.1 Linear Search 228

      6.5.2 Kd-tree Search 230

6.6 Performance Evaluation 232

      6.6.1 Database 232

      6.6.2 Evaluation Setup 234

      6.6.3 Validation of the Parameter Value 237

      6.6.4 Evaluation 239

6.7 Comparison with Existing Work 251

6.8 Summary 252

7 Multimodal Biometric Data Indexing 257

7.1 Feature Extraction 259

7.2 Score Calculation 261

7.3 Reference Subject Selection 262

      7.3.1 Sample Selection 262

      7.3.2 Subject Selection 264

7.4 Reference Score Calculation 266

7.5 Score Level Fusion 267

      7.5.1 Score Normalization 267

      7.5.2 Score Fusion 268

7.6 Index Key Generation 270

7.7 Storing 272

      7.7.1 Index Space Creation 272

      7.7.2 Storing Multimodal Biometric Data 273

7.8 Retrieving 275

7.9 Rank Level Fusion 278

      7.9.1 Creating Feature Vector for Ranking 279

      7.9.2 SVM Ranking 279

7.10 Performance Evaluation 282

      7.10.1 Database 282

      7.10.2 Evaluation Setup 285

      7.10.3 Training of SVM-based Score Fusion Module 286

      7.10.4 Training of SVM-based Ranking Module 286

      7.10.5 Validation of the Parameter Values 287

      7.10.6 Evaluation 290

7.11 Comparison with Existing Work 296

7.12 Summary 298

8 Conclusions and Future Research 305

8.1 Dimensionality of Index Key Vector 305

8.2 Storing and Retrieving 308

8.3 Performance of Indexing Techniques 310

8.4 Threats to Validity 312

      8.4.1 Internal Validity 312

      8.4.2 External Validity 314

      8.4.3 Construct Validity 314

8.5 Future Scope of Work 315

Index 323

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