🤔 many cryptographic scheme(계획/제도/책략) have 'real world analogues'
e.g.) signature -> digital signitures
locks and keys -> public/private key

by case

수업 ppt 그냥 그대로 쭉 읽으면 댐 (사료중심의 example들 나열)

by period

Ancient period

transposition of letters substitution

• Greek Caesar shift cipher : replace latters
• Greeks letters into numbers

Technical Period

machine used for substitution

• enigma

Modern Period

Most Mathmatical & Computational

• Shannon : "a mathmatical theory of cryptography"
• DES : data encryption standard (create a hidden cipher text from a plaintext bits through series of complicated operations)
• Diffie-Hellmen Key Exchange : asymmetric cryptography. very significant step.

Hello Future

• network security is increasingly becoming important
• many new security problems aries