47 lines
1.3 KiB
Python
47 lines
1.3 KiB
Python
from cStringIO import StringIO
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flag = "wh3n_y0u_h4ve_p&q_RSA_iz_ez"
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def modx(base,exp,mod):
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r = 1;
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while (exp > 0):
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if (exp % 2 == 1):
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r = (r * base) % mod
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base = (base * base) % mod
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exp = exp/2
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return r
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def probprime(s):
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while (modx(2,s-1,s) != 1 or modx(3,s-1,s) != 1 or modx(5,s-1,s) != 1 or modx(7,s-1,s) != 1):
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s += 1
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return(s)
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def get_problem(random):
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# add Probable Prime function later
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p = probprime(random.randint(10**39,9*10**39))
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q = probprime(random.randint(10**39,9*10**39))
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e = 3
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salt = "".join([random.choice("0123456789abcdef") for i in range(8)])
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return (p, q, e, salt)
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def generate_ciphertext(random):
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p, q, e, salt = get_problem(random)
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encoded = int(("easyctf{%s_%s}" % (flag, salt)).encode('hex'),16)
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ciphertext = 'p: '+str(p)+'\n'
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ciphertext += 'q: '+str(q)+'\n'
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ciphertext += 'e: '+str(e)+'\n'
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ciphertext += 'c: '+str(pow(encoded, e, p*q))+'\n'
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return StringIO(ciphertext)
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def generate(random):
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return dict(files={
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"ciphertext_rsa1.txt": generate_ciphertext
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})
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def grade(random, key):
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n, salt = get_problem(random)
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if key.find("%s_%s" % (flag, salt)) >= 0:
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return True, "Correct!"
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return False, "Nope."
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