Chair Professor ChinChen Chang National Tsing Hua University

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視覺密碼與數位簽章 Chair Professor Chin-Chen Chang (張真誠) National Tsing Hua University (清華大學) n National Chung

視覺密碼與數位簽章 Chair Professor Chin-Chen Chang (張真誠) National Tsing Hua University (清華大學) n National Chung Cheng University (中正大學) n Feng Chia University (逢甲大學) http: //msn. iecs. fcu. edu. tw/~ccc n 1

How to Share a Secret (t, n)-threshold Scheme n Ex: (2, 3)-threshold Scheme (The

How to Share a Secret (t, n)-threshold Scheme n Ex: (2, 3)-threshold Scheme (The secret k=7) 3 shadows: (1, 9), (2, 0), (3, 2) y (1, 9) (2, 0) (3, 2) x 2

How to Share a Secret (t, n)-threshold Scheme Ex: (3, 5)-threshold Scheme (t=3, n=5,

How to Share a Secret (t, n)-threshold Scheme Ex: (3, 5)-threshold Scheme (t=3, n=5, k=13, p=17) Bob Alice ID 1=1 ID 2=2 (1, 8) Ken Jesse ID 3=3 (3, 10) ID 4=4 Eva ID 5=5 (5, 11) Lagrange Interpolation k 3

The Secret Image: Airplane Hidden in The Basis Image: Mickey Hidden in The Counterfeit

The Secret Image: Airplane Hidden in The Basis Image: Mickey Hidden in The Counterfeit Image: Minnie 4

The Basis Image: Mickey The Counterfeit Image: Minnie The Expanded Basis Image: Mickey-3 X

The Basis Image: Mickey The Counterfeit Image: Minnie The Expanded Basis Image: Mickey-3 X 3 The Expanded Counterfeit Image: Minnie-3 X 3 5

Mickey-3 X 3 Minnie-3 X 3 Airplane 6

Mickey-3 X 3 Minnie-3 X 3 Airplane 6

Experimental Results shadow 1 shadow 2 cover image 1 stego image 1 cover image

Experimental Results shadow 1 shadow 2 cover image 1 stego image 1 cover image 2 stego image 2 7

stego image 1 stego image 2 stacked result 8

stego image 1 stego image 2 stacked result 8

shadow 1 shadow 2 cover image 1 cover image 2 stego image 1 stego

shadow 1 shadow 2 cover image 1 cover image 2 stego image 1 stego image 2 9

stego image 1 stego image 2 stacked result 10

stego image 1 stego image 2 stacked result 10

Progressive Visual Cryptography (t, 6) (2, 6) (3, 6) (4, 6) (5, 6) (6,

Progressive Visual Cryptography (t, 6) (2, 6) (3, 6) (4, 6) (5, 6) (6, 6) 11

Progressive & Meaningful Visual Cryptography n Meaningful shares: friendly content … secret image shadow

Progressive & Meaningful Visual Cryptography n Meaningful shares: friendly content … secret image shadow 1 shadow n camouflage … cover image stego image 1 stego image n 12

Experimental Results (2, 6) (3, 6) (4, 6) (5, 6) (6, 6) 13

Experimental Results (2, 6) (3, 6) (4, 6) (5, 6) (6, 6) 13

Experimental Results shadow image 1 shadow image 2 stacked image 2 14

Experimental Results shadow image 1 shadow image 2 stacked image 2 14

Visual cryptography (Cont. ) Rotating 40 o Stacking Share 2 Share 1 Secret 1

Visual cryptography (Cont. ) Rotating 40 o Stacking Share 2 Share 1 Secret 1 “VISUAL” Secret 2 “SECRET” 15

三、數位簽章 The Model of Digital Signature Signer’s secret key Verification Function Signature Message Signer’s

三、數位簽章 The Model of Digital Signature Signer’s secret key Verification Function Signature Message Signer’s public key Message Check Message=? Message

RSA Public Key Cryptosystem and Digital Signature Scheme q RSA Digital Signature Scheme v

RSA Public Key Cryptosystem and Digital Signature Scheme q RSA Digital Signature Scheme v Sign Function: Signature S=Md mod N. v Verification Function: M=Se mod N. q Example 1. P=11, Q=13, N=143, and (143)=120. 2. e=103, then d=7 (for 103× 7 mod 120=1 ). 3. Sign for M=3: S=37 mod 143=42. 4. Verification: M= Se mod N = 42103 mod 143=3.

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