We have now smoothly completed our hard fork which is now active past block 60,000. The hard fork resolves several bugs and also greatly improves the security of Zerocoin through fixes in our implementation and also libzerocoin, the cryptographic library which enables Zerocoin.
Prior to the hard fork being completed, there was an exploit that resulted in additional Zerocoin spends being generated. The team detected the problem quickly and deployed mitigating measures which were successful. A further emergency update through v0.13.3.1 completely halted the problem by disabling Zerocoin spends and which will be re-enabled automatically past the hard fork which resolves this issue.
The exploit resulted in 18,171 coins being generated (~0.5% of circulating supply or ~0.08% of total supply). We will adjust tail end mining rewards to maintain total supply at 21.4 million. We would like to thank all the pools and exchanges who were very quick to deploy this fix and thank them for their cooperation. This disclosure could only be made now to prevent further people taking advantage of the exploit until the hard fork rolled over.
Our hard fork also marks the release of libzerocoin v2 that is a significant security update to the original libzerocoin library. We recommend all projects using Zerocoin to reach out to us for details on these fixes for those that haven’t done so already. These changes may affect our peers to various degrees and we are happy to help where we can. In a later post, we will cover in further detail the important changes that libzerocoin v2 entails.
Our team has worked hard to resolve this issue and we greatly appreciate our passionate community’s support. Please do not hesitate to reach out to us on Discord!