這裡我整理了一些考試資訊

但我不保證會考喔!

再額外補充三點

One-time Pad Cipher
(單次金鑰使用密碼法)
缺點：光要製造無窮的隨機數字金鑰便相當地耗時，更有複製以及發送端協調的問題，故難以落實

Diffusion跟Confusion

In cryptography, confusion and diffusion are two properties of the operation of a secure cipher which were identified by Shannon in his paper, "Communication Theory of Secrecy Systems" published in 1949.

In Shannon's original definitions, confusion refers to making the relationship between the key and the ciphertext as complex and involved as possible; diffusion refers to the property that redundancy in the statistics of the plaintext is "dissipated" in the statistics of the ciphertext.

簡單來說Confusion要表達的就是，再加密的時候

就是把Key跟PlainText之間的編碼，弄得越複雜越不相干越好

就是要做到盡量互相關係讓人猜不著Key~差不多就這樣XD~

Diffusion is associated with dependency of bits of the output on bits of the input. In a cipher with good diffusion, flipping an input bit should change each output bit with a probability of one half (this is termed the Strict Avalanche Criterion).

簡單來說DIffusion要表達的就是，再加密的時候

就是因為Plaintext在電腦內是有很多的Bit數組成的字串，那Key也是

而Diffusion要傳達的就是，可以擴散，擴散之意就是

第一個Bit數可以引響第二個，第二個影響第三個...etc

也就是可以盡量的影響後面的編碼，這樣就可以讓人猜不出密碼

至於下面這個...本來是覺得頗無聊的東西...

但是因為錄音老師是真的有講啦...那還是看一下吧...

5種攻擊...我不需要翻譯了吧- -

Cryptanalytic Attacks

1.ciphertext only
only know algorithm & ciphertext, is statistical, know or can identify plaintext
2.known plaintext
know/suspect plaintext & ciphertext
3.chosen plaintext
select plaintext and obtain ciphertext
4.chosen ciphertext
select ciphertext and obtain plaintext
5.chosen text
select plaintext or ciphertext to en/decrypt

注意：Linux更新了~可以看了

還有OSI之前要是有上課交作業應該都有寫吧~我就先不另外放了~

以下是這次考試會用到的投影片

所需要用的程式