It takes a lot of energy to mine popular cryptocurrencies such as bitcoin (). That’s why researchers are working to develop blockchain algorithms that are lighter on the grid.
Bitcoin mining alone uses as much energy as Chile consumes, according to . In the past 12 months, the estimated terawatt hours per year consumed by bitcoin mining has risen from 13.66 TWh to 71.12 TWh, according to the website.
Proof of useful work makes it feasible for large data centers to become miners without dramatically increasing their computing overhead.
Bitcoin and many other popular digital currencies rely on something called a (PoW) model, in which computers on a blockchain compete against one another to solve complex mathematical problems. The one that solves a problem first gets to add a new block containing recent transactions to the chain and is rewarded with freshly “mined” cryptocurrency.
‘Game of Chance’
“In PoW, miners guess values,” Ittay Eyal, an assistant professor at Israel’s Technion and the associate director of the , tells ThirtyK. “For each value, they calculate a hash function to see whether it’s a legal value. It’s a game of chance.”
Eyal and his colleagues have developed a different approach, however, called (PoUW). In this system, computers can be used for any desired workload such as complex calculations used in scientific research, and they simultaneously contribute their work toward securing a blockchain. Basically, PoUW uses a central processing unit’s (CPU) normal instructions as the puzzle, rather than requiring it to perform additional work.
Proof of useful work makes it feasible for data centers with large quantities of CPUs to become miners without dramatically increasing their computing overhead.
“Miners using PoUW might be doing long tasks for their own goals, such as protein folding or machine learning,” Eyal, the lead developer, explains. “Each machine instruction is accounted for (just like PoW instructions), but is performing useful work. The miner’s computer randomly decides whether any of those instructions results in a legal block.”
To prevent scams, PoUW uses (TEE) like those created by (SGX) chips, which allow applications to set aside private regions of code and data. This ensures that processes execute correctly and confidentially in a protected address space, thus providing hardware-level security against attacks on the host machine.
Eyal, proof of useful work’s lead developer, says that if a CPU is doing its normal work and no blockchain mining, it has few computations that aren’t necessary for the task at hand or that are redundant (computational waste). As a baseline, Eyal and colleagues at Cornell gave this a wastage value of 1.0. A CPU using the proof-of-useful-work algorithm to mine and do their useful work will have a wastage value of 1.1. The widely used proof-of-work and Lazy PoET algorithms, by contrast, each have computational wastage values of 4.2 because most of their computations are used only for mining.
Eyal says the team is “looking at secure waste reduction in blockchain with and without Intel’s SGX chip. There are at least four or five public projects using our solution, including the payment network.”
Other Energy Savers
PoUW is only one of several energy-efficient blockchain algorithms. Some (PoS) algorithms also promise dramatically reduced energy usage. Rather than having miners solve computational puzzles to validate transactions and create new blocks, as in PoW, people mine or validate transactions depending on how many coins they hold. Currently, PoS algorithms are used by .
(originally called Spacecoin) takes a completely different approach. Rather than performing calculations, it proves the CPUs have certain quantities of disk space. Developed by researchers at MIT and IST Austria, this “nothing at stake” approach generates blocks within 30 seconds and verifies them within one second. Energy usage to mine one SpaceMint is estimated to be one-sixth that of mining one bitcoin.