Added Caesar Cipher Algorithm

Author: manthan0227

Ciphers/Caesar Cipher/Caeser_Cipher.py

@@ -0,0 +1,51 @@
+import string
+
+# Ceaser Cipher
+# plain text: A B C D.... (if key is 3) || ascii value: 65, 66, 67, 68
+# cipher text: D E F G     (adding the key to the ascii value) || ascii value: 68, 69, 70, 71
+
+
+class CaeserCipher:
+    def __init__(self, key=3):
+        self.key = key%26   # whatever the key value it is append to the ascii value of the letter
+
+        # e is dictonary in which every key element store the item as ascii value of key element + key
+        # for storing the lowercase items
+        self.e = dict(zip(string.ascii_lowercase, string.ascii_lowercase[self.key:]+string.ascii_lowercase[:self.key]))  # {'a': 'd', 'b': 'e'.......'z':'c'}
+        #for storing the uppercase items
+        self.e.update(dict(zip(string.ascii_uppercase, string.ascii_uppercase[self.key:]+string.ascii_uppercase[:self.key])))  # After updating the e {'a': 'd', 'b': 'e'.......'z': 'c', 'A': 'D', 'B':'E',.....'Z':'C'}
+
+        # same as above description
+        self.d = dict(zip(string.ascii_lowercase[self.key:]+string.ascii_lowercase[:self.key],string.ascii_lowercase))
+        self.d.update(dict(zip(string.ascii_uppercase[self.key:]+string.ascii_uppercase[:self.key], string.ascii_uppercase)))
+
+    # encryption function
+    def encryption(self, plaintext):
+        ans = [] # To store the letters of the encrypted message
+        for letter in plaintext: # iterate every letter of the plain text
+            if letter in self.e:
+                ans.append(self.e[letter])
+            else:
+                letter
+        return ''.join(ans)
+
+    # decryption function
+    def decryption(self, ciphertext):
+        ans = []    # To store the letters of the decrypted message
+        for letter in ciphertext: # iterate every letter of the cipher text
+            if letter in self.d:
+                ans.append(self.d[letter])
+            else:
+                letter
+        return ''.join(ans)
+
+print("Input the Key: ")
+key = int(input(""))
+c = CaeserCipher(key) # Default key value is 3 but you can change value of key
+print("Enter the Message which you want to Encrypt: ")
+plain_text = input("")  # plain text which we have to enter the message
+print("Original text: ",  plain_text)
+encrypted_text = c.encryption(plain_text)  # encrypted text which is return by the encryption function
+print("Encrypted text: ", encrypted_text)
+decrypted_text = c.decryption(encrypted_text)  # decryption text which is return by the decryption function
+print("Decrypted text: ", decrypted_text)

Ciphers/Caesar Cipher/Images/Output_1.png

@@ -0,0 +1,46 @@
+
+# Ceaser_cipher
+### Aim 
+To Implement the Ceaser cipher 
+
+### Purpose
+- The Ceaser cipher Algorithm is simple to understand and implement.
+  This is used to Encrypt the message and Decrypt the message.
+
+### Description
+
+- In cryptography, a Caesar cipher also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. 
+  It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet.
+
+### Workflow
+- The complete process depends on length of the alphabets used.
+- The letter of an alphabet of size m are first mapped to the integers in the range 0...m-1.
+- Each letter of a given text is replaced by a letter some fixed number of positions down the alphabet. 
+- For example with a shift of 1, A would be replaced by B, B would become C, and so on. The method is apparently named after Julius Caesar, who apparently used it to communicate with his officials. 
+- Thus to cipher a given text we need an integer value, known as shift which indicates the number of position each letter of the text has been moved down. 
+- The encryption can be represented using modular arithmetic by first transforming the letters into numbers, according to the scheme, A = 0, B = 1,…, Z = 25. Encryption of a letter by a shift n can be described mathematically as. 
+ 
+### Compilation Steps
+
+- Download the file Ceaser_cipher.py
+- Run the File Ceaser_cipher.py
+- Input any key
+- Input the Message 
+- And finally we will get Encrypted message and Decrypted Message
+
+# Outputs
+
+### Output 1
+![Output_1](https://user-images.githubusercontent.com/78487398/135653838-f537c782-875b-4c1a-aef7-3dd7dc8c315b.png)
+
+
+### Output 2
+![Output_2](https://user-images.githubusercontent.com/78487398/135654075-6a373e48-ecb1-403f-8da5-520ed9eb31d9.png)
+
+
+### Output 3
+![Output_3](https://user-images.githubusercontent.com/78487398/135654147-e97beaed-c5d0-4d8c-8548-6ec2a6df17d1.png)
+
+### Author
+[Manthan Nagpurkar](https://github.com/manthan0227)
+