picoctf/crypto/substitution0/solve.py

108 lines
2.4 KiB
Python
Executable File

#!/usr/bin/env nix-shell
#!nix-shell -i python -p python3
# NOTE: the colors are used to keep track of which letters have been
# already substituted, and which are still unknown.
def green(s):
return f"\033[42m{s}\033[0m"
def red(s):
return f"\033[41m{s}\033[0m"
def substitute(cipher_text, substitution_map):
for letter in cipher_text:
if letter.lower() in substitution_map:
if letter.isupper():
x = substitution_map[letter.lower()].upper()
else:
x = substitution_map[letter]
print(green(x), end="")
else:
print(red(letter), end="")
with open('message.txt', 'r') as file:
enc = file.read()
# Here, I will be slowly substituting the letters in the ciphertext
# based on what I believe the words to be. I have commented out the
# invocations of substitute, and commented the newly found letters
# after each invocation.
# Starting off, "pvncDCM{...}" looks like "picoCTF{...}"
substitution_map = {
'0': '0',
'1': '1',
'2': '2',
'3': '3',
'4': '4',
'5': '5',
'6': '6',
'7': '7',
'8': '8',
'9': '9',
'-': '-',
'_': '_',
'\n': '\n',
' ': ' ',
',': ',',
'.': '.',
':': ':',
';': ';',
'{': '{',
'}': '}',
'p': 'p',
'v': 'i',
'n': 'c',
'c': 'o',
'd': 't',
'm': 'f',
}
# substitute(enc, substitution_map)
# 'Dsu fxow ij' -> 'The flag is'
substitution_map['d'] = 't'
substitution_map['s'] = 'h'
substitution_map['u'] = 'e'
substitution_map['x'] = 'l'
substitution_map['o'] = 'a'
substitution_map['w'] = 'g'
substitution_map['j'] = 's'
# substitute(enc, substitution_map)
# 'taligg all thiggs igto cogsifeaatiog' -> 'taking all things into consideration'
# 'rhich' -> 'which'
substitution_map['l'] = 'k'
substitution_map['g'] = 'n'
substitution_map['f'] = 'd'
substitution_map['a'] = 'r'
substitution_map['r'] = 'w'
# substitute(enc, substitution_map)
# 'roynd hlack spots' -> 'round black spots'
# 'ekceedinglq' -> 'exceedingly'
substitution_map['y'] = 'u'
substitution_map['h'] = 'b'
substitution_map['q'] = 'y'
substitution_map['k'] = 'x'
# substitute(enc, substitution_map)
# 'iery reearkable' -> 'very remarkable'
# 'pribe' -> 'pride'
# 'Zupiter' -> 'Jupiter'
substitution_map['i'] = 'v'
substitution_map['e'] = 'm'
substitution_map['b'] = 'd'
substitution_map['z'] = 'j'
substitute(enc, substitution_map)