OneRNG is a random number generator that you can use for cryptography – it’s completely open source, secure but hackable:
The board is designed to be physically inspected – there’s no traditional cover, instead we have a metal RF shield with a removable lid. The metal can is there to stop in internal noise from escaping, but equally to make sure that the internal circuits cannot be interfered with by outside influences. The lid is so you can look inside and make sure the board contains the components you expect. You can also inspect the traces on the top and bottom of the printed circuit board to see if they match our published layout.
via OneRNG – an open source entropy generator by Paul Campbell – Moonbase Otago — Kickstarter.
Interesting design but the use of the CC2531 seems odd. Why didn’t you just use a part like the MAXQ1010 or MaxQ1050 from Maxim? They have excellent hardware random number generators in silicon and you wouldn’t have needed a shield.