crypto: add a few more challenges

crypto/basic_mod1/message.txt

@@ -0,0 +1 @@
+128 322 353 235 336 73 198 332 202 285 57 87 262 221 218 405 335 101 256 227 112 140 

crypto/basic_mod1/solve.py

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+#!/usr/bin/env python3
+
+# Take each number mod 37 and map it to the following character set: 0-25 is the alphabet (uppercase), 26-35 are the decimal digits, and 36 is an underscore.
+
+with open('message.txt') as file:
+    content = file.read().strip()
+
+print("picoCTF{", end="")
+for n in content.split(' '):
+    number = int(n)
+    number %= 37
+    if number < 26:
+        print(chr(number + ord('A')), end="")
+    elif number >= 26 and number < 36:
+        print(number - 26, end="")
+    elif number == 36:
+        print('_', end="")
+    else:
+        print()
+        print(f"Code author seems to have forgotten a number.... {number}")
+        exit(1)
+print("}")

crypto/interencdec/enc_flag

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+YidkM0JxZGtwQlRYdHFhR3g2YUhsZmF6TnFlVGwzWVROclgya3lNRFJvYTJvMmZRPT0nCg==

crypto/interencdec/flag.txt

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+1. base64 decode
+2. remove surroudning b''
+3. base64 decode
+4. ROT13 (value 19)
+
+picoCTF{caesar_d3cr9pt3d_b204adc6}

crypto/read_my_cert/readmycert.csr

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+-----BEGIN CERTIFICATE REQUEST-----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+-----END CERTIFICATE REQUEST-----

crypto/read_my_cert/solve.sh

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+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p bash openssl
+
+openssl req -noout -text -in 'readmycert.csr' | grep -o 'picoCTF{.*}'

crypto/rotation/encrypted.txt

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+xqkwKBN{z0bib1wv_l3kzgxb3l_555957n3}

crypto/rotation/flag.txt

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+Cyberchef ROT13 (value 18):
+picoCTF{r0tat1on_d3crypt3d_555957f3}

crypto/substitution0/message.txt

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+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

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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, "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)

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)

crypto/substitution2/message.txt

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+nafyffoxenefufytpqnafymfppfentkpxeafbaxraezaqqpzqgswnfyefzwyxnhzqgsfnxnxqlexlzpwbxlrzhkfystnyxqntlbwezhkfyzatppflrfnafefzqgsfnxnxqlevqzwesyxgtyxphqlehenfgetbgxlxenytnxqlvwlbtgflntpemaxzatyfufyhwefvwptlbgtycfntkpfecxppeaqmfufymfkfpxfufnafsyqsfyswysqefqvtaxraezaqqpzqgswnfyefzwyxnhzqgsfnxnxqlxelqnqlphnqnftzautpwtkpfecxppekwntpeqnqrfnenwbflnexlnfyfenfbxltlbfozxnfbtkqwnzqgswnfyezxflzfbfvflexufzqgsfnxnxqletyfqvnflptkqyxqwetvvtxyetlbzqgfbqmlnqywllxlrzafzcpxenetlbfofzwnxlrzqlvxrezyxsneqvvflefqlnafqnafyatlbxeaftuxphvqzwefbqlfospqytnxqltlbxgsyquxetnxqltlbqvnflatefpfgflneqvspthmfkfpxfuftzqgsfnxnxqlnqwzaxlrqlnafqvvflexuffpfgflneqvzqgswnfyefzwyxnhxenafyfvqyftkfnnfyufaxzpfvqynfzafutlrfpxegnqenwbflnexltgfyxztlaxraezaqqpevwynafymfkfpxfufnatntlwlbfyentlbxlrqvqvvflexufnfzalxiwfexefeeflnxtpvqygqwlnxlrtlfvvfznxufbfvfleftlbnatnnafnqqpetlbzqlvxrwytnxqlvqzweflzqwlnfyfbxlbfvflexufzqgsfnxnxqlebqfelqnpftbenwbflnenqclqmnafxyflfghtefvvfznxufphtenftzaxlrnafgnqtznxufphnaxlcpxcftltnntzcfysxzqznvxetlqvvflexufphqyxflnfbaxraezaqqpzqgswnfyefzwyxnhzqgsfnxnxqlnatneffcenqrflfytnfxlnfyfenxlzqgswnfyezxflzftgqlraxraezaqqpfyenftzaxlrnafgflqwratkqwnzqgswnfyefzwyxnhnqsxiwfnafxyzwyxqexnhgqnxutnxlrnafgnqfospqyfqlnafxyqmltlbfltkpxlrnafgnqkfnnfybfvflbnafxygtzaxlfenafvptrxesxzqZNV{L6Y4G_4L41H515_15_73B10W5_8F1KV808}

crypto/substitution2/solve.py

@@ -0,0 +1,144 @@
+#!/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, "sxzqZNV{...}" 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',
+    '_': '_',
+    '{': '{',
+    '}': '}',
+    's': 'p',
+    'x': 'i',
+    'z': 'c',
+    'q': 'o',
+    'n': 't',
+    'v': 'f',
+}
+
+# substitute(enc, substitution_map)
+
+# Using frequency analysis (https://www.dcode.fr/frequency-analysis), we find that:
+
+# F	175×	13.87%
+# N	125×	9.9%
+# X	103×	8.16%
+# Q	102×	8.08%
+# L	98×	7.77%
+# E	83×	6.58%
+# T	68×	5.39%
+# Z	63×	4.99%
+# Y	61×	4.83%
+# A	56×	4.44%
+# P	46×	3.65%
+# W	42×	3.33%
+# V	39×	3.09%
+# G	35×	2.77%
+# B	34×	2.69%
+# S	28×	2.22%
+# R	24×	1.9%
+# U	20×	1.58%
+# H	19×	1.51%
+# K	16×	1.27%
+# M	9×	0.71%
+# C	9×	0.71%
+# O	5×	0.4%
+# I	2×	0.16%
+
+# Based on this, and the frequency of letters in the english alphabet, we can guess for 'e'
+
+substitution_map['f'] = 'e' # 13.87% ~= 12.7%
+
+# 'petitiol' -> 'petition'
+
+substitution_map['l'] = 'n'
+
+# 'incpwbinr' -> 'including'
+# 'effectiue' -> 'effective'
+
+substitution_map['p'] = 'l'
+substitution_map['w'] = 'u'
+substitution_map['b'] = 'd'
+substitution_map['r'] = 'g'
+
+# 'encountey' -> 'encounter'
+
+substitution_map['y'] = 'r'
+
+# 'eecurith' -> 'security'
+
+substitution_map['e'] = 's'
+substitution_map['h'] = 'y'
+
+# 'effectiuely' -> 'effectively'
+
+substitution_map['u'] = 'v'
+
+# 'cogputer' -> 'computer'
+
+substitution_map['g'] = 'm'
+
+# 'catllenge' -> 'challenge'
+
+substitution_map['a'] = 'h'
+substitution_map['t'] = 'a'
+
+# 'thinc' -> 'think'
+
+substitution_map['c'] = 'k'
+
+# 'valuakle' -> 'valuable'
+
+substitution_map['k'] = 'b'
+
+# 'thereeoists' -> 'there exists'
+
+substitution_map['o'] = 'x'
+
+# 'homever' -> 'however'
+
+substitution_map['m'] = 'w'
+
+# 'techniiue' -b 'technique'
+
+substitution_map['i'] = 'q'
+
+substitute(enc, substitution_map)
+

crypto/vigenere/flag.txt

@@ -0,0 +1,4 @@
+rgnoDVD{O0NU_WQ3_G1G3O3T3_A1AH3S_cc82272b}
+
+From cyberchef:
+picoCTF{D0NT_US3_V1G3N3R3_C1PH3R_ae82272q}