crypto: add a few more challenges

crypto/substitution1/message.txt

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+ZWDg (gejfw djf zacwpfx wex dqar) afx a wscx jd zjicpwxf gxzpfbws zjicxwbwbjv. Zjvwxgwavwg afx cfxgxvwxm hbwe a gxw jd zeaqqxvrxg hebze wxgw wexbf zfxawbybws, wxzevbzaq (avm rjjrqbvr) gnbqqg, avm cfjtqxi-gjqybvr atbqbws. Zeaqqxvrxg pgpaqqs zjyxf a vpitxf jd zawxrjfbxg, avm hexv gjqyxm, xaze sbxqmg a gwfbvr (zaqqxm a dqar) hebze bg gptibwwxm wj av jvqbvx gzjfbvr gxfybzx. ZWDg afx a rfxaw has wj qxafv a hbmx affas jd zjicpwxf gxzpfbws gnbqqg bv a gadx, qxraq xvybfjvixvw, avm afx ejgwxm avm cqasxm ts iavs gxzpfbws rfjpcg afjpvm wex hjfqm djf dpv avm cfazwbzx. Djf webg cfjtqxi, wex dqar bg: cbzjZWD{DF3LP3VZS_4774ZN5_4F3_Z001_4871X6DT}

crypto/substitution1/solve.py

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+#!/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, "wex dqar bg: cbzjZWD{...}" looks like "the flag is: 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',
+    ' ': ' ',
+    ',': ',',
+    '.': '.',
+    ':': ':',
+    ';': ';',
+    '{': '{',
+    '}': '}',
+    '(': '(',
+    ')': ')',
+    'w': 't',
+    'e': 'h',
+    'x': 'e',
+    'd': 'f',
+    'q': 'l',
+    'a': 'a',
+    'r': 'g',
+    'b': 'i',
+    'g': 's',
+    'c': 'p',
+    'z': 'c',
+    'j': 'o',
+}
+
+# substitute(enc, substitution_map)
+
+# '(shoft fof captpfe the flag) afe a tspe' -> '(short for capture the flag) are a type'
+# 'coipetitiov' -> 'competition'
+
+substitution_map['f'] = 'r'
+substitution_map['p'] = 'u'
+substitution_map['s'] = 'y'
+substitution_map['i'] = 'm'
+substitution_map['v'] = 'n'
+
+# substitute(enc, substitution_map)
+
+# 'presentem hith' -> 'presented with'
+# 'numter' -> 'number'
+# 'security snills' -> 'security skills'
+
+substitution_map['m'] = 'd'
+substitution_map['h'] = 'w'
+substitution_map['t'] = 'b'
+substitution_map['n'] = 'k'
+
+# substitute(enc, substitution_map)
+
+# 'seryice' -> 'service'
+# 'FR3LU3NCY' -> 'FR3QU3NCY'
+
+substitution_map['y'] = 'v'
+substitution_map['l'] = 'q'
+
+substitute(enc, substitution_map)