Merge branch 'master' of github.com:failedxyz/easyctf

listen-closely/description.md

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+We intercepted a secret message, but we can't tell what it's saying. Maybe you can help? [super secret message](${listenclosely_wav})?

listen-closely/grader.py

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+def grade(autogen, key):
+    if key.find("CAN_YOU_EVEN_HEAR_ME_YET") != -1:
+        return True, "Correct!"
+    return False, "Nope!"

listen-closely/problem.yml

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+author: GenericNickname
+title: Listen Closely
+hint: 1, 16, 8000
+category: Crytpography
+autogen: false
+programming: false
+value: 50
+files:
+  - listenclosely.wav

rsa2/description.md

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+Some more RSA! This time, there's no P and Q... [this](${ciphertext_txt}).

rsa2/grader.py

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+from cStringIO import StringIO
+
+flag = "l0w_n"
+
+def modx(base,exp,mod):
+    r = 1;
+    while (exp > 0):
+        if (exp % 2 == 1):
+            r = (r * base) % mod
+        base = (base * base) % mod
+        exp = exp/2
+    return r
+
+def probprime(s):
+    if s%2==0:
+        s += 1
+    smolprimes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]
+    while len(set([modx(i,s-1,s) for i in smolprimes])) != 1 or modx(2,s-1,s) != 1:
+        s+=2
+    return(s)
+
+def get_problem(random):
+    # add Probable Prime function later
+    p = probprime(random.randint(10**20,9*10**20))
+    q = probprime(random.randint(10**20,9*10**20))
+    e = 3
+    salt = "".join([random.choice("0123456789abcdef") for i in range(4)])
+    return (p, q, e, salt)
+
+def generate_ciphertext(random):
+    p, q, e, salt = get_problem(random)
+    encoded = int(("flag{%s_%s}" % (flag, salt)).encode('hex'),16)
+    ciphertext =  'n: '+str(p*q)+'\n'
+    ciphertext += 'e: '+str(e)+'\n'
+    ciphertext += 'c: '+str(pow(encoded, e, p*q))+'\n'
+
+    return StringIO(ciphertext)
+
+def generate(random):
+    return dict(files={
+        "ciphertext_rsa2.txt": generate_ciphertext
+    })
+
+def grade(random, key):
+    n, salt = get_problem(random)
+    if key.find("%s_%s" % (flag, salt)) >= 0:
+        return True, "Correct!"
+    return False, "Nope."

rsa2/problem.yml

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+title: RSA 2
+value: 35
+author: neptunia
+autogen: true