It's the Caesar code. (*‘▽‘*)*

Catalog

introduction

The story

Thought analysis

Code implementation

Analysis of the code

Letter

Write it at the end

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introduction

Through the ages , People never stop Access to information And Protection of information （ encryption ）. And in history , There is a well-known encryption method ; This encryption method also gave rise to the later encryption methods 、 Development provides a useful reference .“ What is this encryption method ？ yes , Caesar code .”

“ that , What is the Caesar code ？ How do we understand it ？ In this post , Maybe , You'll find out .”

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The story

……

Caesar: "V'z fbeel gb urne gung lbh'ir pnhtug n pbyq, Pvpreb."

A few days later.

Cicero: "Nsgre erfg n srj qnlf, V sryy zhpu orggre, abj."

……

After watching the dialogue between Caesar and Cicero , Do you think it's cloudy ？ Feeling , Full of the feeling of Martian ……“ That's because Caesar and Cicero encrypted the contents of the letter .”

that , Is there any way we can crack their letter （ although , This is a bit immoral .）？

……

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Thought analysis

1. The core idea of Caesar's code , yes , According to the alphabet , Change the order of letters , So as to realize the encryption of text .
2. Let's start with letters “A” For example .
3. We know , The English alphabet has a total of 26 Letters , that , You know , remove “A” after , There is still left 25 Letters .
4. such , It will be easy for us to understand —— When will “A” The position of moves to the right 26 When a , We are back to our original position “A”.
5. “ reflection , If we only move 13 Who? ？”
6. Alphabet “A” To the right 13 position , Find letter “N”（ Did you find , Letter “N” And then to the right 13 position , We get the letters “A” What about it ？）.
7. Naturally , With 13 For the key , We can achieve letters “A” And letters “N” Mutual reference to .

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Code implementation

# -*- coding: utf-8 -*-

# Created by Violet. All rights reserved!

#%%
#  Call function library .

import time as t

#%%
#  Create the alphabet .

Alp = dict()

for y in (65,97): # Unicode In the encoding  "A"&"a"  The coding .
    
    for x in range(26): #  Traverse 26 Letters .
    
        Alp[chr(x + y)] = chr(((x + 13) % 26) + y)
    
#print(Alp)    

#%%        
#  Import text , encryption / Decrypt .

while True:

    Txt = input("Encrypt or decrypt?")
    
    t.sleep(0.3)
    
    print("")

    print("".join(Alp.get(txt,txt) for txt in Txt))
    
    t.sleep(0.4)
    
    #  continue ？
    
    print("\nPress Q/q to exit. (*'▽'*)*")
    
    t.sleep(0.4)
    
    Ans = input('Que: Shall we continue?')
    
    if Ans in {"Q","q"}:
        
        break
    
    else:
        
        print("")
        
        pass

#%%
# To be continued.

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Analysis of the code

1. ……
2. Since you want to encrypt the text / Decrypt , So first of all , We need an alphabet （ For translation ）.“ therefore , In encryption / Before decryption , We have to make such an alphabet first .”
3. stay “Unicode code ” in ——“A” The code of is “65”;“a” The code of is “97”.
4. “chr() function ”： Find the string corresponding to the encoding ;“ord() function ”： Find the encoding corresponding to the string .
5. “ reflection , Such a question .”
6. The alphabet is used for translation , The format for “A” Express “N”, And so on. . that , What kind of （ Tuples ？ list ？ aggregate ？ Dictionaries ？） To make this alphabet ？ Dictionaries ！
7. “ Teaching a man to fish is better than giving him a fish .” therefore , Understanding of the code that created the alphabet , I hope the readers will come down and think .
8. ……
9. Alp.get(txt,txt) for txt in Txt  It means —— Traverse “Txt character string ” Each of them “txt character ”, use “get() function ” From the alphabet “Alp” Find the corresponding value in , If there is , Return the corresponding value , If not, return to the original “txt” value .
10. "".join(Alp.get(txt,txt) for txt in Txt) It means , Connect the translated characters （ As for why there are no spaces in quotation marks , because , There are already spaces in the text you entered , When translating, the blank space is also reserved , therefore , There is no need to add any more space .）
11. ……
12. When we have to translate many texts , Press again and again “F5 key ” Would it be too much trouble ？ trouble .“ therefore , We used one While loop , however , Remember to set the exit path .”
13. then , When we try to run the program , Find out , The display speed is a little fast , It's weird ,, that , Let's use “ Time bank time” Come and help us （t.sleep()）.
14. To be continued.
15. ……

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Letter

that , What did Caesar and Cicero say ？

……

Caesar: " I'm sorry to hear that you've caught a cold, Cicero."

Cicero: "After rest a few days, I feel much better, now."

……

（ Beep warning , It's a bad habit to pry into other people's privacy .）

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Write it at the end

• “ Cuddle wood , Born in the end . Platform on the ninth floor , From tired soil . A journey , Begins with a single step .”
• I want to go to the north pole to see the aurora , I want to take a walk in the Sahara desert , I want to dive in the Great Barrier Reef , I want to go to Hawaii , I want to punch in the statue of liberty ……“ You also have many places you want to go ？ that , Let's make up our minds to be better .”