130 likes | 301 Views
Multiple layer data hiding scheme for medical images. Source: Computer Standards & Interfaces Authors: Der-Chyuan Lou, Ming-Chiang Hu and Jiang-Lung Liu Speaker: Chia-Chun Wu ( 吳佳駿 ) Date: 2008/11/14. Outline. Introduction Review of difference expansion embedding
E N D
Multiple layer data hiding scheme for medical images Source: Computer Standards & Interfaces Authors: Der-Chyuan Lou, Ming-Chiang Hu and Jiang-Lung Liu Speaker: Chia-Chun Wu (吳佳駿) Date: 2008/11/14
Outline • Introduction • Review of difference expansion embedding • The proposed method • The experimental results • Conclusions
Cover image Introduction • Image Steganography Interceptor Sender Secret data: 0101… Secret data: 0101… Public channel (Ex: Internet) Receiver Stego-image Cover image
Embedding: Review of difference expansion embedding (1/3) • Tain’s reversible data embedding method (DE) Pixel pair (206, 201) Pixel pair (x, y) m=203, d=5, b=1 d'=(101b)2→(1011)2=11 x'=203+6=209, y'=203-5=198 New pixel pair (209,198)
Review of difference expansion embedding (2/3) • Tain’s reversible data embedding method (DE) New pixel pair (209,198) Pixel pair (206, 201) m=203, d'=11 m=203, d=5, b=1 d'=11= (1011)2→b=1 d'=(101b)2→(1011)2=11 d= (101)2=5 x'=203+6=209, y'=203-5=198 x'=203+3=206, y'=203-2=201 New pixel pair (209,198) Original pixel pair (206, 201)
55 10 255 127 128 m=200 0 m=10 Review of difference expansion embedding (3/3) • Overflow and underflow • Overflow: (255, 254) → (256, 254) • Underflow: (1, 0) →(1, -1) • Solution: expandable
Cover image Reduce DE Stego-image The proposed method (1/3) • Multiple-layer embedding concept Cover image DE Stego-image • The visual quality of embedded image will be drastically degraded • Cause the underflow or overflow problem • Decrease the hiding capacity
h'=5-21=3, b=1 h'=(101b)2→(1011)2=11 h''=(11b)2→(111)2=7 x'=203+6=209, y'=203-5=198 x'=203+4=207, y'=203-3=200 New pixel pair (207,200) Location map = 1 The proposed method (2/3) Pixel pair (206, 201) reduce m=203, h=5, b=1 New pixel pair (209,198)
The proposed method (3/3) New pixel pair (207, 200) Location map = 1 m=203, h'=7 h=3+21=5 h'=7= (111)2→b=1 x'=203+3=206, y'=203-2=201 h'=3 Original pixel pair (206, 201)
Problem • Double location map size • 512×512 image • 131072 + 65536 = 196608 bits = 0.75 bpp 512×256 512×256×50% The first location map (1: expandable, 0: changeable) (50% expandable, 50% changeable) The second location map 119628+113266-2*65536=101822 bits
Conclusions • The proposed method has remarkable improvement in the visual quality of the embedded image • The proposed method provide high-capacity