Bitcoin Mining the Hard Way: With Paper and Pencil

By Inside Bitcoins Sep 28, 2014 5:33 PM EST

bitcoin mining by hand
bitcoin mining with paper and pencil

Shirriff’s calculations

NEW YORK (InsideBitcoins) — Bitcoin mining equipment is expensive and often outmoded before it processes its first block. Industrial mining is rapidly becoming the norm, as deep-pocketed operations replace the homebrew miner.

But can mining be accomplished simply with paper and pencil, rather than racks and racks of water-cooled servers? Ken Shirriff, a computer programmer with Google, wanted to find out.

“I decided to see how practical it would be to mine Bitcoin with pencil and paper,” Shirriff writes on his blog. “It turns out that the SHA-256 algorithm used for mining is pretty simple and can in fact be done by hand. Not surprisingly, the process is extremely slow compared to hardware mining and is entirely impractical. But performing the algorithm manually is a good way to understand exactly how it works.”

[See also: What is Bitcoin Mining?]

“Bitcoin mining is a key part of the security of the Bitcoin system,” Shirriff adds. “The idea is that Bitcoin miners group a bunch of Bitcoin transactions into a block, then repeatedly perform a cryptographic operation called hashing zillions of times until someone finds a special extremely rare hash value. At this point, the block has been mined and becomes part of the Bitcoin block chain. The hashing task itself doesn’t accomplish anything useful in itself, but because finding a successful block is so difficult, it ensures that no individual has the resources to take over the Bitcoin system.”

His initial calculations took 16 minutes and 45 seconds.

“At this rate, hashing a full Bitcoin block (128 rounds) would take 1.49 days, for a hash rate of 0.67 hashes per day (although I would probably get faster with practice). In comparison, current Bitcoin mining hardware does several terahashes per second, about a quintillion times faster than my manual hashing. Needless to say, manual Bitcoin mining is not at all practical.”

Bitcoin mining powered by donuts

And surprisingly, though human-powered, not very energy efficient.

“There’s not much physical exertion, so assuming a resting metabolic rate of 1500kcal/day, manual hashing works out to almost 10 megajoules/hash. A typical energy consumption for mining hardware is 1000 megahashes/joule. So I’m less energy efficient by a factor of 10^16, or 10 quadrillion,” Shirriff says. “The next question is the energy cost. A cheap source of food energy is donuts at $0.23 for 200 kcalories. Electricity here is $0.15/kilowatt-hour, which is cheaper by a factor of 6.7 – closer than I expected. Thus my energy cost per hash is about 67 quadrillion times that of mining hardware. It’s clear I’m not going to make my fortune off manual mining, and I haven’t even included the cost of all the paper and pencils I’ll need.”

For the technically-inclined, Shirriff posted a YouTube video of the process.

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