凱撒密碼pythin密碼

Caesar cipher is one of the well-known techniques used for encrypting the data. Although not widely used due to its simplicity and being more prone to be cracked by any outsider, still this cipher holds much value as it is amongst the firstly developed encryption techniques which gave us the idea of developing the entire encryption and decryption process.

凱撒密碼是用于加密數據的眾所周知的技術之一。 盡管由于其簡單性而未被廣泛使用，并且更容易被任何外人破解，但該密碼仍然具有很大的價值，因為它是最早開發的加密技術之一，使我們有了開發整個加密和解密過程的想法。

Now, talking about its characteristics and details, Caeser cipher is also known as "shift cipher". This is because, in this technique, we just shift the letters of the plain text to a certain number, (which is determined by the key) in a lexicographic order to obtain the ciphertext. The same number of letters in reverse lexicographic order is shifted back in the decryption process to obtain the plain text back.

現在，談到其特征和細節， Caeser密碼也被稱為“移位密碼” 。 這是因為，在這種技術中，我們只是按照字典順序將純文本的字母移動到某個數字(由密鑰確定)以獲取密文。 在解密過程中，將相同數量的字母按逆序字典順序移回以獲取純文本。

The following key points can be drawn for the Caeser cipher,

可以為Caeser密碼得出以下要點，

• Caesar Cipher is also known as a shift cipher.

  凱撒密碼也被稱為移位密碼。

• It is a type of symmetric-key cryptography.

  它是一種對稱密鑰密碼術 。

• It follows the mono-alphabetic cipher, being a part of the substitution cipher.

  它遵循單字母密碼，是替代密碼的一部分。

加密過程 (Encryption Process)

Here, we assume the numbers 0-25 represent the English alphabets in lexicographic order, i.e. from a to z.

在這里，我們假設數字0-25代表按字母順序排列的英語字母，即從a到z 。

Suppose, we have number denoting the letters of plain text denoted by 'P', and a key, say 'K' (Note that it is better to choose key within the range of alphabets: 0 to 25).

假設我們有一個數字，表示由'P'表示的純文本字母，一個鍵稱為'K' (請注意，最好在字母范圍0到25之間選擇鍵)。

Therefore, the encryption on the plain text to convert it into ciphertext is performed as follows,

因此，對純文本進行加密以將其轉換為密文的過程如下：

    E (P, K) = ( P + K ) mod 26

解密過程 (Decryption Process)

Here also, the numbers 0-25 represent the English alphabets in lexicographic order, i.e. from a to z, and we choose the same key 'K' that we used to encrypt our data. Suppose we denote the numbers representing the letters of the ciphertext using 'C'.

同樣，這里的數字0-25表示按字母順序排列的英語字母，即從a到z ，我們選擇用于加密數據的相同密鑰“ K” 。 假設我們用'C'表示代表密文字母的數字。

The decryption of the ciphertext to convert it back into plain text is performed as follows,

解密密文以將其轉換回純文本的過程如下：

    D (C, K) = ( C - K ) mod 26

示例問題 (Example Problem)

    Given Plain text: 'HELLO'Key: 3Convert the given plain text into ciphertext:Solution:We write all the numbers associated with every letter of the plain text:H   :  7E   :  4L   :  11O   :  14Therefore, applying the Caeser cipher for each letter:E(H,3) = ( 7 + 3 ) mod 26= 10    = KE(E, 3) = ( 4 + 3) mod 26=  7    = HE(L, 3) = ( 11 + 3) mod 26=  14   = OE(O, 3) = ( 14 + 3) mod 26=  7    = RTherefore, the ciphertext that we get for the word 'HELLO' is 'KHOOR'.

Note: You can cross-check your answer by applying the decryption process over the ciphertext, and if it comes back to be the same as the plain text, then it means that our answer is correct.

注意：您可以通過對密文應用解密過程來交叉檢查您的答案，如果它與純文本相同，則表明我們的答案是正確的。

翻譯自: https://www.includehelp.com/cryptography/caesar-cipher.aspx

凱撒密碼pythin密碼