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October 17, 2019 23:39
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| #Vigenere Cipher | |
| alphabet_pos = {'A':0, 'a':0, 'B':1, 'b':1, 'C':2, 'c':2, 'D':3, 'd':3, | |
| 'E':4, 'e':4, 'F':5, 'f':5, 'G':6, 'g':6, 'H':7, 'h':7, 'I':8, 'i':8, | |
| 'J':9, 'j':9, 'K':10, 'k':10, 'L':11, 'l':11, 'M':12, 'm':12, 'N': 13, | |
| 'n':13, 'O':14, 'o':14, 'P':15, 'p':15, 'Q':16, 'q':16, 'R':17, 'r':17, | |
| 'S':18, 's':18, 'T':19, 't':19, 'U':20, 'u':20, 'V':21, 'v':21, 'W':22, | |
| 'w':22, 'X':23, 'x':23, 'Y':24, 'y':24, 'Z':25, 'z':25 } | |
| def alphabet_position(letter): | |
| alphabet_pos = {'A':0, 'a':0, 'B':1, 'b':1, 'C':2, 'c':2, 'D':3, | |
| 'd':3, 'E':4, 'e':4, 'F':5, 'f':5, 'G':6, 'g':6, 'H':7, 'h':7, 'I':8, | |
| 'i':8, 'J':9, 'j':9, 'K':10, 'k':10, 'L':11, 'l':11, 'M':12, 'm':12, | |
| 'N': 13, 'n':13, 'O':14, 'o':14, 'P':15, 'p':15, 'Q':16, 'q':16, | |
| 'R':17, 'r':17, 'S':18, 's':18, 'T':19, 't':19, 'U':20, 'u':20, 'V':21, | |
| 'v':21, 'W':22, 'w':22, 'X':23, 'x':23, 'Y':24, 'y':24, 'Z':25, 'z':25 | |
| } | |
| pos = alphabet_pos[letter]+1 | |
| return pos | |
| def rotate(letter, rot): | |
| shift = 97 if letter.islower() else 65 | |
| return chr((ord(letter) + rot - shift) % 26 + shift) | |
| def encryptwithrepeatation(text, key): | |
| encrypted = [] | |
| starting_index = 0 | |
| for letter in text: | |
| # if it's alphanumerical, keep it that way | |
| # find alphabet position | |
| rotation = alphabet_position(key[starting_index]) | |
| # if it's a space or non-alphabetical character, append and move on | |
| if not letter in alphabet_pos: | |
| encrypted.append(letter) | |
| elif letter.isalpha(): | |
| encrypted.append(rotate(letter, rotation)) | |
| #if we've reached last index, reset to zero, otherwise + by 1 | |
| if starting_index == (len(key) - 1): | |
| starting_index = 0 | |
| else: | |
| starting_index += 1 | |
| return ''.join(encrypted) | |
| dict1 = {'A': 0, 'B': 1, 'C': 2, 'D': 3, 'E': 4, | |
| 'F': 5, 'G': 6, 'H': 7, 'I': 8, 'J': 9, | |
| 'K': 10, 'L': 11, 'M': 12, 'N': 13, 'O': 14, | |
| 'P': 15, 'Q': 16, 'R': 17, 'S': 18, 'T': 19, | |
| 'U': 20, 'V': 21, 'W': 22, 'X': 23, 'Y': 24, 'Z': 25} | |
| dict2={0:'A',1:'B',2:'C',3:'D',4:'E', | |
| 5:'F',6:'G',7:'H',8:'I',9:'J', | |
| 10:'K',11:'L',12:'M',13:'N',14:'O', | |
| 15:'P',16:'Q',17:'R',18:'S',19:'T', | |
| 20:'U',21:'V',22:'W',23:'X',24:'Y',25:'Z'} | |
| #This function generates the key in | |
| #a cyclic manner until it's length isi'nt | |
| #equal to the length of original text | |
| def generate_key(message,key): | |
| x=len(message) | |
| i=0 | |
| while True: | |
| if x==i: | |
| i=0 | |
| if len(key)==len(message): | |
| break | |
| key+=key[i] | |
| i+=1 | |
| return key | |
| #This function returns the encrypted text | |
| #generated with the help of the key | |
| def cipherText(message,key_new): | |
| cipher_text='' | |
| i=0 | |
| for letter in message: | |
| if letter==' ': | |
| cipher_text+=' ' | |
| else: | |
| x=(dict1[letter]+dict1[key_new[i]])%26 | |
| i+=1 | |
| cipher_text+=dict2[x] | |
| return cipher_text | |
| #This function decrypts the encrypted text | |
| #and returns the original text | |
| text = input("Enter some text:") | |
| key = input("Enter a key:") | |
| print (encryptwithrepeatation(text, key)) | |
| key_new=generate_key(text,key) | |
| cipher_text=cipherText(text,key_new) |
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