In the end, I think applying these privacy and anonymity technologies to every blockchain out there is going to be essential because to limit freedom of expression, to limit freedom of association, you don’t only have to deal with prior restraint. If you have the freedom to transact with everyone, but all your transactions are visible to everyone, then you can be punished after the fact for transacting with the wrong people, which essentially robs you of your freedom to transact. We have to realise that privacy is a foundational human right and without it, freedom of association, freedom of (political) expression, all go away. - Andreas Antonopolous

Brief History of Digital Privacy

If privacy is outlawed, then only outlaws will have privacy. - Philip R. Zimmermann, Why I Wrote PGP

Designed to empower individual rights, Pretty Good Privacy (PGP) was published on the Internet in 1991 by Phil Zimmermann. PGP is an encryption program that provides cryptographic privacy and authentication for data communication. By open sourcing PGP, Zimmermann violated the US export restrictions for cryptographic software, putting him at the center of a brutal criminal investigation that spanned nearly half a decade. In 1996, the US government dropped its case against Zimmermann, but the fight for privacy was far from over. As Zimmermann recounts in Why I Wrote PGP, “the only way to hold the line on privacy in the information age is strong cryptography”.

Although the struggle for control over digital interactions has not abated, progress on the implementation of cryptography has enabled the de facto encryption of communication over the Internet via SSL (Secure Socket Layer) and TLS (Transport Layer Security). When these protocols were first introduced, there was much of the same criticism that we see today in the form of “encryption enables criminal activity” and “you shouldn’t be scared if you have nothing to hide”. While these arguments may seem appealing on the surface, they ignore history by assuming trust in the underlying system and everyone else that uses it.

This is a mistake. To foster an environment in which people can be truly safe, we must aspire towards systems in which the requirement of trust itself is minimized. Blockchain technology is a step in the right direction; it minimizes trust in the underlying system by incentivizing cooperation among a network’s stakeholders [1]. Still, most contemporary blockchains operate as open public ledgers, displaying transaction data pseudonymously. This can lead to critical leaks of user identity. To alleviate this problem and uphold digital privacy in all forms, it bears repeating the vision first set out by Eric Hughes in A Cypherpunk Manifesto: “privacy in an open society requires anonymous transaction systems…An anonymous system empowers individuals to reveal their identity when desired and only when desired; this is the essence of privacy”.

[1] see explanations by (i) Vitalik and (ii) Preethi for a more nuanced explanation of how blockchains minimize trust

Zcash

Building on decades of research, Zcash was developed and launched by top cryptographers from MIT, Technion, John Hopkins, Tel Aviv University, and UC Berkeley. Zcash is a blockchain that ensures complete confidentiality of transaction data. Zero-knowledge proofs allow transactions to be verified without revealing the sender, receiver or transaction amount.