Shufflebox.

Two known rows expose a hidden permutation. Invert it once, recover the censored input, then prove the answer by running every row forward again.

FIELD Beginner cryptoARTIFACT 16 positions × 3 rowsSTATUS Reproduced offline

01 / METHOD

The order was the only secret.

The organizer's program shuffles input positions. It uses the same 16-position order for three rows and leaves each character unchanged.

Label each source index. In the first known input, four-character blocks identify its group. In the second, repeating abcd identifies the position in that group.
Read the outputs together. Each pair of output characters matches exactly one pair in the two known inputs, revealing all 16 source indices.
Invert the third row. Put each character from the censored output back at its recovered source index.
Check forward. Reapply the recovered order to the two known inputs and recovered third input. All three outputs must match the handout byte for byte.

RECOVERED MAPPING16 / 16 INDICES

input indices in output order

09 10 00 08 11 13 03 06
15 05 14 07 04 02 12 01

known row A → 16 / 16 matched
known row B → 16 / 16 matched
censored row → 16 / 16 matched

The mapping is derived from the two known pairs. The recovered row matches the published censored output.

02 / RESULT + VERIFICATION

One answer.
Three exact checks.

Restoring the third input yields a 16-character phrase. The organizer's archived answer confirms the same value.

DUCTF{udiditgjwowsuper}

Historical challenge answer. No platform submission, rank, or prize is claimed.

Known row A re-encodes exactly
Known row B re-encodes exactly
Recovered row re-encodes exactly
Organizer archive confirms the flag

Official challenge ↗Official handout ↗Solver + writeup ↓

Shufflebox.

The order was the only secret.

One answer.Three exact checks.

One answer.
Three exact checks.