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I've continued to stay interested in alt-currencies, and, recently, a new one caught my eye: Riecoin. Named after Riemann, the proof-of-work in this currency is finding dense clusters of primes starting at a number n, where there are six primes "in a row": n, n+4, n+6, n+10, n+12, and n+16. To solve a block, you do some hashing of the block contents just as in Bitcoin, and use it to generate a "target" number. The proof-of-work is then to find a prime chain within a certain numerical distance above the target number.

Continue on da-data.blogspot.comI plan on a more technical post about the process of optimizing the search for these (you can see some discussion of it on the Riecoin bitcointalk thread if you really want). It's quite fun, but at this point, it still boils down to relatively straightforward prime sieving for huge numbers (1200-1300 bits).

There's one very important thing to understand about such sequences, though, before going further: They only appear at certain positions relative to multiples of lots of primes. For example, using the "primorial" 210 (2*3*5*7), a match can only occur at position 97. You can take this up to larger primorials if you want to. Using this search strategy can drastically speed a miner.

Instead, I wanted to look at the evolution of the mining ecosystem for a very young coin. It was born only a month ago, and the first cut miner was slow. The "difficulty" started out at about 304, as you can see, for example, in Block 1. This block was solved by a miner who found the prime number

16309310251386080651589092357489796440346150213043000915553887348582623387213161684406947617

as the start of a chain of six. For block 1, the prime was found at an "offset" of 0x2858cf21 relative to the target. I'm leaving it in hex so that you can see by examination that it's a 32 bit number. I point that out, because this is one of the best clues about how a miner is behaving: The first-released cpuminer could only f...