The Eurocrypt 2013 gift is a scytale, an ancient Greek cryptographic mechanism. The message is written in a leather strip across the length of the secret-key which is a stick of certain diameter. The diameter determines the secret-key.

The puzzle of the conference asks participants to figure out another phrase that can be used in the same way. Due to the fact that wrapping the leather strip around different scytales produces collisions, a number of constraints are defined as explained in the puzzle definition page.

Fig. 2. The leather strip decrypted across the three different secret-keys: revealing “Security can be a mythos you spy on”

Each conference participant received one of three scytales and a common leather strip that decrypted differently when wrapped around each of the three secret-keys. The three resulting plaintexts assembled together in a phrase that was the motto of the conference.

Fig. 1. A Eurocrypt 2013 scytale with its engraving visible.