Chair Professor ChinChen Chang National Tsing Hua University

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

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 Ex: (3, 5)-threshold Scheme (t=3, n=5,

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

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

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

stego image 1 stego image 2 stacked result 8

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

stego image 1 stego image 2 stacked result 10

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

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

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

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

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

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

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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 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 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, 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 Image: Minnie 4

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

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

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

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 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 shadow image 1 shadow image 2 stacked image 2 14

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 public key Message Check Message=? Message

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.