[Cryptography] Python Caesar 암호

전역변수

- ENC : 암호화

- DEC : 복호화

from functools import reduce

ENC = 0

DEC =1

def makeDisk(key):

keytable = map(lambda x: (chr(x+65), x),range(26))

key2index = {}

for t in keytable:

alphabet, index = t[0],t[1]

key2index[alphabet] = index

if key in key2index:

k = key2index[key]

else:

return None,None

enc_disk = {}

dec_disk = {}

for i in range(26):

enc_i = (i+k)%26

enc_ascii = enc_i + 65

enc_disk[chr(i+65)] = chr(enc_ascii)

dec_disk[chr(enc_ascii)] = chr(i+65)

return enc_disk, dec_disk

def caesar(msg, key, mode):

ret = ''

msg = msg.upper()

enc_disk, dec_disk = makeDisk(key)

if enc_disk is None:

return ret

if mode is ENC:

disk = enc_disk

if mode is DEC:

disk = dec_disk

for c in msg:

if c in disk:

ret += disk[c]

else:

ret += c

return ret

def main():

plaintext = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

key = 'F'

print('Original:\t%s' %plaintext.upper())

ciphertext = caesar(plaintext, key, ENC)

print('Caesar Cipher:\t%s' %ciphertext)

deciphertext = caesar(ciphertext, key, DEC)

print('Deciphered:\t%s' %deciphertext)

if __name__=='__main__':

main()