We have proven conclusively by the exhaustive search of all possible rulers that the previously predicted 27-mark ruler is indeed the most optimal one. We were confident that we would find a more optimal ruler during this search, but it was not to be.

The best known ruler is 27/3-12-26-25-29-2-9-36-10-68-1-4-17-53-35-8-16-28-6-14-13-71-18-19-23-7 (length 553). Represented the other way, this is marks at positions 0 3 15 41 66 95 97 106 142 152 220 221 225 242 295 330 338 354 382 388 402 415 486 504 523 546 553.

In total, we verified 302,621,586 unique stubs (2,526 with 3-diffs, 179,120 with 4-diffs, 6,457,815 with 5-diffs and 295,982,125 with 6-diffs).

Final participant and team stats results for OGR-27 are pretty impressive: Distributed Amiga finished third overall, out of 896 teams! Also, and perhaps more surprisingly, the largest individual contributor overall (i.e. from all 19919 participants), is a team member going by the name "[distributed amiga] Erik" :) Well done Erik!

What does the future hold? Obviously there is OGR-28 so you can continue to contribute as before (with the same client as for OGR-27). If you are still participating in the RC5-72 effort, please stop. It has become counterproductive for a number of reasons. First of all, besides the fact that the challenge has officially been dropped by RSA Labs themselves almost 7(!) years ago now, there is also the inescapable zeitgeist: the Snowden revelations have confirmed that RSA has accepted $10 million from the NSA to secretly include a backdoor in their products as early as 2004 and therefore taints the company and any ongoing promotion through continueing with an RC5 effort. This is diametrically opposed to the original intent of their own challenges.

Secondly, many more worthwhile efforts and distributed projects have emerged since then. If you do not want to participate in a scientific project like OGR, proteine folding related efforts and similar, there are interesting alternatives like securing the networks of cryptocurrencies such as Bitcoin. Since this is public domain/open source and aligns with many of the Distributed Amiga philosophies I have briefly pondered an 'Amicoin', but do not think there is presently the critical mass to (securely) support this. Although I personally believe Bitcoin has a future as a payment system (amongst others, the currency aspect only scratches the surface of the protocol's possibilities, think distributed, secure, anonymous p2p everything, filesharing, mail, DNS, contracts, etc.), if you are interested in this beyond that I suggest looking at alternatives that either use algorithms designed to prevent technological races to the bottom (through FPGA/ASIC implementation) such as Litecoin (which uses scrypt), or ones with scientific value like Riecoin/Primecoin (using Riemann hypothesis/Fermat test proofs of work to find prime numbers). There are two added benefits above RC5: the mining process for many of these currencies generates at least partial return on investment (electricity cost), and perhaps more importantly supports a future of (amongst others) financial sovereignty, regardless of any immediate benefits like being much cheaper and faster than traditional transaction methods. Take care though that apart from the main ones there are already dozens of more or less useless or shady alternatives and more surfacing every day ("doggy" coin..), and that this is definitely not investment advice.