def encrypt(message, key):
    cipher = ""
    
    for i in range(len(message)):
            char = message[i]
            keychar = key[i]
            
            if (char.isupper()):
                cipher += chr((ord(char) + ord(keychar) - 130) % 26 + 65)
                
            else:
                cipher += chr((ord(char) + ord(keychar) - 194) % 26 + 97)
        
    return cipher

def decrypt(cipher, key):
    message = ""
    
    for i in range(len(cipher)):
            char = cipher[i]
            keychar = key[i]
            
            if (char.isupper()):
                message += chr((ord(char) - ord(keychar) - 130) % 26 + 65)
                
            else:
                message += chr((ord(char) - ord(keychar)) % 26 + 97)
                
    return message
    
def newkey(text, key):
    newkey = ""
    length = 1
        
    while length <= len(text):
        for i in range(len(key)):
            if length <= len(text):
                newkey += key[i]
                length += 1
            else:
                break;
    return newkey
    
x = 1
while(x==1):
    print("1.Caesar Cipher \n 2.Vernam Cipher \n 3.Vigenere Cipher \n 4.Transposition Cipher \n 5.RSA \n")
    Choice = int(input("Choose one of the options above: "))
 
    if Choice == 1:
        print("\n1.Encrypt a message \n 2.Decrypt a message\n")
        option = int(input("Choose one option from above: "))
    
        if option == 1:
            cipher = ""
            message = input("Enter your message: ")
            shift = int(input("Enter the shift value: "))
        
            for i in range(len(message)):
                char = message[i]
            
                if (char.isupper()):
                    cipher += chr((ord(char) + shift - 65) % 26 + 65)

                else:
                    cipher += chr((ord(char) + shift - 97) % 26 + 97)
                
            print("Your cipher text = ",cipher)
 
        if option == 2:
            message = ""
            cipher = input("Enter your Cipher text: ")
            shift = int(input("Enter the shift value: "))
        
            for i in range(len(cipher)):
                char = cipher[i]
            
                if (char.isupper()):
                    message += chr((ord(char) - shift - 65) % 26 + 65)
        
                else: 
                    message += chr((ord(char) - shift - 97) % 26 + 97)
            print("Your decrypted message = ",message)
 
    elif Choice == 2:
        print("1.Encrypt a message")
        print("2.Decrypt a cipher")
        option = int(input("Choose one option from above: "))
    
        if option == 1:
            message = input("Enter your message : ")
            key = input("Enter the key: ")
        
            print("Your cipher text = ",encrypt(message, key))
        
        elif option == 2:
            cipher = input("Enter the cipher text: ")
            key = input("Enter the key: ")
        
            print("Your decrypted message = ",decrypt(cipher, key))
 
    elif Choice == 3:
        print("1.Encrypt a message")
        print("2.Decrypt a cipher")
        option = int(input("Choose one option from above: "))
    
        if option == 1:
            message = input("Enter your message: ")
            key = input("Enter the key: ")
        
            key = newkey(message, key)
            print("Your cipher text = ",encrypt(message,key))
        
        elif option == 2:
            message = ""
            cipher = input("Enter the cipher text: ")
            key = input("Enter the key: ")
        
            key = newkey(cipher, key)
            print("Your decrypted message = ",decrypt(cipher,key))
            
    opt = input("\nDo you want to continue?(y/n): ")
    if opt == 'n':
        x = 0
    elif opt == 'y':
        x = 1