1994年Naor和Shamir提出視覺加解密方式,基本上此種方式是門檻方法的
一個應用,它的基本雛型簡單言之包含一個存在於紙上的資訊M和一張做為
秘密金匙的投影片S,當M和S重疊時藉由人眼便能得知秘密影像為何.傳統
的加解密系統在加解密的過程中,都須要藉助電腦的運算,並非是由人腦所
能駕馭,所以相對而言視覺加解密的方式就顯得簡單的多了,解密過程只須
重疊投影片,不過Naor和Shamir所提的是屬於類似隨用即丟之方式,可能是
這次做完加解密程序後就不再重覆使用相同的金匙解密.在此提出架構在
視覺加解密理論的加解密系統,這是一個對稱性加解密系統,不過建構方式
是別於已往的運算方式而以Naor和Shamir的方式取代之.和傳統加解密系
統不同的是通訊的資料是影像,利用此點我們可用傳真機傳遞資料以增簡
便性.在這篇論文的第二章是介紹視覺加解密的理論及所用到的基礎概念,
第三章談利用Naor和Shamir的方式來架構出一套加解密系統並探討金匙的
持續使用性,而第四章的多人共用秘密影像係利用第三章的概念所構築而
成,我們將這架構和DES做比較,第五章根據傳統金匙加解密系統的優缺點
來探討第三章所提之系統,第六章為結論.
In 1994,Naor and Shamir proposed Visual Cryptography (VC) theory
that is anapplication of threshold scheme. To put it simply ,
the prototype of VC c-onsists of a printed page of ciphertext
and a printed transparency serves as decrpted key. Upon
receiving the ciphertext, we can stack the ciphertext and the
transparency to gain the secret with eyes . In conventional
cryptosystem , we have to do crypting operation with the
computer. Ho-wever , it is simple for human to do decrypting
operation in VC,because we can stack transparencies to achieve
the decrypting operation. The method of Na-or and Shamirs'' is
like one time pad , it does not do the crypting operationwith
the same key.We propose a cryptosystem based on visual
cryptographictheory of Naor and Shamir . We construct this
cryptosystem as a symm-etric one , naturally, it bases on VC
theory .In this structure, we can u-se fax machine to achieve
communication .