Dvdes-631 !!install!!

f(user_key) -> bool

We see the flag format, confirming the binary will simply puts the flag once the right key is supplied. dvdes-631

We start from the expected ciphertext:

MAGIC = 0x5A5A5A5A5A5A5A5A sub0 = 0x1F2E3D4C5B6A7988 user_key = ((sub0 ^ MAGIC) & 0xFFFFFFFFFFFFFFFF) >> 1 | ((sub0 ^ MAGIC) & 1) << 63 f(user_key) -&gt; bool We see the flag format,

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