A Hybrid Digital-Signature and Zero-Watermarking Approach for Authentication and Protection of Sensitive Electronic Documents

Table 2

Comparison of features and benefits between watermarking methods.

Concept/metric	Traditional watermark approaches	Zero-watermarking approach [1]	Zero-watermarking approach [35]	Zero-watermarking approach [34]	Zero-watermarking approach [33, 36]	Proposed watermarking method
Overhead (additional)	Proportional to embedded key size	None	None	None	None	None
Embedding mode	Format-encoding	Logical: zero-watermark encoding	Logical: zero-watermark encoding	Logical: zero-watermark encoding	Logical: zero-watermark encoding	Logical: zero-watermark encoding
Location of watermark message ()	Embedded in	Embedded in	Embedded in	Embedded in	Embedded in	Embedded in
Processing and embedding decision	Based on searching through text for candidate words, lines, and spaces	Based on double-letter words in English language	Based on sentence entropy	Based on the first letter with specific word lengths	Based on comparing Unicode summations	Based on comparing Unicode summations and logical operations
Compatible with various formats?	Limited	Yes, only English character support needed	Supports Chinese language only	Supports English language only	Yes, host-document language character support/Unicode needed	Yes, host-document language character support/Unicode needed
Language-dependent	No	Yes	Yes	Yes	No	No
Document- authenticity verification	No	Yes	Yes	Yes	Yes	Yes
Tamper-detection and identification capabilities	No	No	No	Yes	No	Yes
Integrity robustness	Weak	Strong	Strong	Strong	Strong	Strong
Perceptibility performance	Low-medium	High	High	High	High	High
Capacity ratio performance	Inversely proportional to perceptual similarity	High	High	High	High	High
Capability to extract publishers watermark logo	No	Yes	No	No	No	Yes