CyberWorld / training station / cryptography

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Tier 02 / five local challenges

Crypto Lab

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MISSION OBJECTIVERecover, verify, and explain five artifacts. Enter a result or use a lab tool; each confirmation stays in this browser tab.

Crypto Mission Context

Work through five deliberately small cryptography exercises: factor, decrypt, verify, find a collision, and decode.

These are toy or public test artifacts, not keys or payloads for a real system. Use the optional hints if you get stuck.

F11 Factor n = 3233 PENDING

The published RSA-toy modulus is n = 3233 with public exponent e = 17. Factor n by trial division (try every prime up to √n ≈ 56.86); submit either prime.

Need a factorization hint?

Try primes below √3233. If one divides evenly, check that the quotient is prime too. A second hint: test a prime in the low fifties.

F12 RSA-toy decryption PENDING

Ciphertext c = 352, public key (e=17, n=3233), private exponent d = 2753. Recover the plaintext integer m = c^d mod n.

m = pow(c, d, n)
  = 352^2753 mod 3233

How do I compute this without huge numbers?

Use repeated squaring with a modulus after every multiplication. In Python, pow(352, 2753, 3233) performs the same calculation.

F13 ECDSA P-256 signature verification PENDING

A NIST P-256 keypair has signed the message below. Verify the signature with WebCrypto's subtle.verify("ECDSA", { hash: "SHA-256" }, ...).

Inspect signed artifact and verification method

message: "Phoenix Operations: May 26 2026"
public:  046b17cc5608f5019e193bebe486935ce357448649545fcbe0409e80081c70cdd18ac691b9ed0f85868f7f83a60439bd90e8dfbfe72c03f49cea612a7d2f4a9b96
sig:     4714f43c994a6e20cc7e345cd7f1451a82f43c79df5b1b2904f2bbf1fd9434fc10eaa55e1cb3d03cc1ed906961911d39e5be8416315bca1ecf656ff9e51c71e2
curve:   P-256 / SHA-256

The browser imports the public key and verifies the signature over the exact message bytes. A valid signature does not prove that the message itself is trustworthy.

Click Verify to run the browser's WebCrypto verifier on the displayed artifact.

F14 16-bit HMAC target collision PENDING

Key cyberworld:F14:hmac16; anchor message Phoenix-2026 hashes to truncated tag HMAC-SHA-256(key, msg)[0:16 bits] = 0x5916. Find any other string whose HMAC has the same 16-bit prefix.

This is a fixed-target second-preimage search, not a birthday search between arbitrary pairs. Expect about 2¹⁶ guesses. The local Search tool reports progress and can be cancelled.

F15 Vigenere break PENDING

Ciphertext (uppercase, no spaces) -- key length 6, key is a 6-letter cryptographer's surname.

ZVASJFRBDSFAZLDRYBJIXVQIKWBVSIYQXTJBDQOMNX

Inspect repeating patterns or try a six-letter candidate key below. The preview tool does not submit your answer.

--/5 confirmed locally