Clear it in 3 steps
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Start the environment
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Investigate the target
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Submit the flag
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Encrypted Communication - GPG Public Key Cryptography
Mission
Practice GnuPG decryption. Import every private key under `/challenge/keys/` and decrypt each ciphertext under `/challenge/messages/`. Only one message -- the one encrypted to the genuine recipient key -- decrypts to a plaintext containing the flag; the others are harmless decoys that can also be isolated by matching the recipient key id. A real GnuPG runs unprivileged.
Hints
Hint 1 Show
You do not know which private key in keys/ matches which ciphertext in messages/; use gpg --list-packets to read each ciphertext's recipient key-id
Hint 2 Show
Use gpg --show-keys to read each private key's id and match it to the recipient
Hint 3 Show
Import all private keys and decrypt every message; only one yields the flag