crypto: add a few more challenges

crypto/substitution0/message.txt

@@ -0,0 +1,12 @@
+OHNFUMWSVZLXEGCPTAJDYIRKQB 
+
+Suauypcg Xuwaogf oacju, rvds o waoiu ogf jdoduxq ova, ogf hacywsd eu dsu huudxu
+mace o wxojj noju vg rsvns vd roj ugnxcjuf. Vd roj o huoydvmyx jnoaohouyj, ogf, od
+dsod dveu, yglgcrg dc godyaoxvjdj—cm ncyaju o wauod pavbu vg o jnvugdvmvn pcvgd
+cm ivur. Dsuau ruau drc acygf hxonl jpcdj guoa cgu ukdauevdq cm dsu honl, ogf o
+xcgw cgu guoa dsu cdsua. Dsu jnoxuj ruau uknuufvgwxq soaf ogf wxcjjq, rvds oxx dsu
+oppuoaognu cm hyagvjsuf wcxf. Dsu ruvwsd cm dsu vgjund roj iuaq aueoalohxu, ogf,
+dolvgw oxx dsvgwj vgdc ncgjvfuaodvcg, V ncyxf soafxq hxoeu Zypvdua mca svj cpvgvcg
+aujpundvgw vd.
+
+Dsu mxow vj: pvncNDM{5YH5717Y710G_3I0XY710G_03055505}

crypto/substitution0/solve.py

@@ -0,0 +1,107 @@
+#!/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)