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A solution is given by Peter Ryan, Crypto Santa. In The New Codebreakers, vol. 9100 of Lecture Notes in Computer Science, pp. 543-549, Springer, 2016. An earlier version (with Sjouke Mauw and Sasa Radomirovic) can be found at (Open access), Security protocols for Secret Santa.


I made a toy cipher that functioned in this manner. It had a bytewise transposition step that was performed by an invertible randomized permutation, similar to the Fisher-Yates shuffle, but easily invertible. Key material was used to select the next "random" index to shuffle, so as to enable decryption. At first, I really liked the idea, figuring that ...

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