The Most Serene Republic, reunited in congress, decided :

That all presently known block ciphers suck ; That an actually useful block cipher is required for our own purposes; That we will consider proposals from barbarians as well as citizens.

Consequently, you are cordially invited to submit a proposal for a block cipher that :

Works on block sizes of 1 kbytes, 4 kbytes, 16 kbytes and 64 kbytes. Bonus points for ciphers that work on an arbitrary block size. Use a 64 kbyte key. Fits In Head Items which come with a proof of hardness, as well as items that eschew basic arithmetic operations as implemented by computers will be particularly favoured. While we will consider purely theoretical proposals, items which come with sample implementation and assorted tests will be preferred.

The rewards will be a 10 BTC payment from me, as well as a honoris causa position in the very Lordship. Let the party begin!

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