A vulnerability that could have permitted an attacker to coin infinite ZEC has been patched and disclosed by the company behind the coin.
Ariel Gabizon, an engineer at the Zerocoin Electric Coin Company — the startup behind privacy-focused cryptocurrency Zcash — reportedly discovered the vulnerability the night before his talk at the Financial Cryptography 2018 conference in March 2018. Gabizon contacted Sean Bowe, a cryptographer at the Zcash Company, the same day.
A fix for the vulnerability was covertly included (to prevent exploitation) in the Sapling network upgrade adopted on Oct. 28, 2018. The bug was contained in the variant of zk-SNARKs — the kind of cryptography that grants anonymity to shielded Zcash transactions — and had been independently implemented by other projects.
Namely, Horizen (previously known as ZenCash) and Komodo blockchains both suffered from the same vulnerability. The Zcash team reportedly “disclosed the impact and fix path of this issue to Horizen’s” security team and Komodo’s developers via encrypted email in mid-November.