24 lines
797 B
Python
24 lines
797 B
Python
import hashlib
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import math
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# Shark is a sha256+xor based encryption.
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# I made it because I want to try to break it.
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# (Precisely: Show it does not provide semantic security, because it is not IND-CPA-secure)
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# This will work iff I succeed in building a PPT-discriminator for sha256 from randomness
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# As my first approach this discriminator will be based on an LSTM-network.
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def xor(ta,tb):
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return bytes(a ^ b for a, b in zip(ta, tb))
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def enc(plaintext, key, iv):
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ciphertext = bytes()
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bs = 256/8
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for i in range(math.ceil(len(plaintext/bs))):
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m = hashlib.sha256()
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m.update(xor(key, iv + i.to_bytes(bs, byteorder='big')))
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k = m.digest()
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ciphertext += sxor(k, plaintext[bs*i:][:bs])
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def dec(ciphertext, key, iv):
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return enc(ciphertext, key, iv)
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