31 lines
825 B
Python
31 lines
825 B
Python
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#!/usr/bin/env python3
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import sys
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def attack(fctxt, pos, plainAtPos, newPlainAtPos):
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f = open(fctxt,"rb")
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ciphertext = f.read()
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f.close()
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plainAtPos = plainAtPos.encode()
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newPlainAtPos = newPlainAtPos.encode()
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txt_len = len(plainAtPos)
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diff = bytes([a ^ b for (a,b) in zip(plainAtPos,newPlainAtPos)])
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cipher_diff = bytes([a ^ b for (a,b) in zip(diff,ciphertext[pos:pos+txt_len])])
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new_ciphertext = ciphertext[:pos] + cipher_diff + ciphertext[pos+txt_len:]
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with open(fctxt+".attck","wb") as f:
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f.write(new_ciphertext)
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def main():
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argv = sys.argv[1:]
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argc = len(argv)
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if argc < 3 or argc > 5:
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sys.exit("Needs 4 arguments <fctxt> <pos> <ptxtAtPos> <newPtxtAtPos>")
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attack(argv[0],int(argv[1]),argv[2],argv[3])
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if __name__ == "__main__":
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main()
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