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38 lines
1.3 KiB
Python
38 lines
1.3 KiB
Python
import sys
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import os
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from itertools import cycle
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import gzip
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def ror(n, rotations, width):
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return (2**width - 1) & (n >> rotations | n << (width - rotations))
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def rol(n, rotations, width):
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return (2**width - 1) & (n << rotations | n >> (width - rotations))
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with open("3/withkey/juliakey.txt", "r") as julia_key_file, open(
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"3/withkey/juliaplaintext.txt.gz.enc", "rb"
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) as julia_cipher_file:
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julia_key_content = julia_key_file.read()
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key_shift = int(julia_key_content.split()[4])
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key_xor = julia_key_content.split()[-1]
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print("key shift", key_shift)
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print("key xor", key_xor)
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julia_cipher_content = julia_cipher_file.read()
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result = bytes()
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for c_byte, k_byte in zip(julia_cipher_content, cycle(key_xor)):
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tmp = c_byte ^ ord(k_byte)
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# kinda misleading, question mentions that encryption rotates bits but didn't mention which direction
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# imagine spending 3 hours thinking it's gzip when it turns out you rotate RIGHT
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result += ror(c_byte ^ ord(k_byte), 1, 8).to_bytes(1, "big")
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# gzip - write as bytes, read with decompression
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with open("test.gz", "wb") as f:
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f.write(result)
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with gzip.open("test.gz", "r") as gf:
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print(gf.read().decode())
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os.remove("test.gz")
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