Tag Archives: Zero-knowledge proof

Censorship Resistant Payment Technologies

On Coin Center’s blog, Matthew Green and Peter van Valkenburgh write:

Censorship resistance is the only way to guarantee that a digital asset truly is “bearer” and can be sent directly from one person to another without reliance on a third party. Cryptocurrencies achieve this property by making network participants (miners) compete for the power to add transactions to the ledger. Even if some miners wish to censor a transaction, we assume that others will not, particularly if it means they are forgoing fee revenue. A centralized digital dollar would not have competitive mining but if the role of the ledger-keeper was reduced to verifying zero-knowledge proofs then any refusal to perform that verification risks indiscriminately censoring users throughout the economy. If the Treasury became corrupt, it could degrade the performance of the network system-wide, but it would be difficult to selectively block certain individuals or surveil their activities.

None of these protections, however, are guaranteed, and new technologies always present unpredictable risks and unintended consequences. We must, therefore, preserve and defend physical cash and should never celebrate its demise. Cash, along with cryptocurrencies, is essential as a payment method of last resort that cannot be surveilled or controlled by corrupt governments or unscrupulous corporations.


The Economist reports about a new digital currency platform, Zcash. The platform could handle more transactions than for example, Bitcoin. The open-source project backed by outside investors offers confidentiality:

Bitcoin obscures the identity of currency owners, but the “blockchain”, the ledger that keeps track of all the coins, is open and can be analysed to see the flows of funds. This is a serious barrier for banks: blockchains could reveal their trading strategies and information about their customers. Zcash, by contrast, shields transactions from prying eyes with a scheme based on “zero-knowledge proofs” (hence the “Z” in its name). These are cryptographic protocols proving that a statement (who owns coins, for instance) is true without revealing any other information (how many and where the money came from). And it is by selling this technology—called “zk-SNARK” (don’t ask)—to banks that Zcash, the company, wants to earn its keep.