Document Liveness¶
Definition¶
Document liveness detects whether a presented document is a physical original or a reproduction — such as a screen display, photocopy, or printed photo of a document. It is the document equivalent of face liveness detection.
What Document Liveness Detects¶
| Attack | Method | Detection Cue |
|---|---|---|
| Screen display | Photo of document shown on phone/tablet screen | Moiré patterns, screen pixel grid, screen bezel, refresh artifacts |
| Photocopy | Black-and-white or color photocopy of document | Halftone dots, reduced contrast, paper texture change |
| Printed photo | High-quality print of document image | Print dot pattern, color gamut shift, paper texture |
| Screenshot | Document image displayed on screen, then screen captured | Screen artifacts, resolution mismatch |
Detection Methods¶
| Method | What It Analyzes |
|---|---|
| Moiré pattern detection | Interference patterns from screen pixel grid captured by camera |
| Halftone detection | Regular dot patterns from photocopier/printer |
| Texture analysis | Original document texture vs paper/screen surface |
| Color analysis | Color gamut differences between original and reproduction |
| Frequency analysis | Specific frequency signatures of screens and printers |
| Reflection analysis | Screen glare and reflection patterns |
| Edge analysis | Screen bezel or paper edge detection around document |
| Deep CNN | Learned features combining all above cues |
Key Takeaways¶
Summary
- Document liveness prevents document replay attacks — showing photos of documents on screens
- Moiré pattern detection is the strongest single cue for screen display detection
- Halftone analysis catches photocopies
- Deep CNN models combining multiple cues achieve best results
- Often combined with document forensics in a single pipeline