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Horizen (Zencash) software update scheduled for release on September 27th 2018

There is a new version of ZEN software (2.0.15) scheduled for release on September 27th, 2018.

All mining pools, node operators, and Swing wallet users must upgrade to ZEN 2.0.15 prior to block 392512 which will occur around midnight on October 10th.

ZEN 2.0.15 replaces the current version 2.0.14, which is set to deprecate (no longer run). The major focus of this version is the new 51% attack prevention feature.

ZEN 2.0.15 replaces the current version 2.0.14, which is set to deprecate (no longer run). The major focus of this version is the new 51% attack prevention feature. This is not a hard fork.


  • 51% attack prevention code
  • Update RPC commands/thread names/messages with new Horizen name
  • Update Horizen logo
  • Fix erroneous log messages on wallet rescan


  • Miners and node operators: ZEND will not work and thus you will not be able to earn ZEN until you upgrade to ZEN 2.0.15
  • Swing wallet users: You will not be able to access your funds until you upgrade to the latest Swing wallet version.

Zen version 2.0.15 is scheduled to be released on September 27th, 2018 to address the upcoming deprecation of the current version on October 10th, 2018.

The release includes the new 51% attack prevention code which has been successfully tested and works as expected. It also includes some backend rebranding updates. Zen 2.0.14 will shut off at block height #392512 around October 10th (near midnight UTC or shortly after) automatically.

All node operators, exchanges, and anyone running the full version will have to update to zen 2.0.15 before then. The new 2.0.15 version will be available at on September 27th by end of the day. Updated versions of the Swing wallet will be available several days after.

Update instructions for node operators and miners will be provided soon.

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ZenCash (Horizen) To Fight Against The 51% Attack

The past two weeks have been an exciting and trying time for the ZenCash (Horizen) team. However, even in the face of adversity, the ZenCash (Horizen) team continues to thrive and deliver on our promises to you, the community.

Approximately two weeks ago, our exchange partner was the victim of a double spend attack, where a malicious actor was able to spend their ZEN twice. Double spends are possible in all proof-of-work chains due to consensus rules inherited from Bitcoin.

This attack targeted the exchange, not the ZenCash (Horizen) blockchain.

We just want to kill this, we don’t want this ever be a problem again for the industry.  – Rob Viglione, Co-founder of ZenCash (Horizen)

This attack ignited the ZenCash (Horizen) team to create a comprehensive protocol level defensive strategy for our project and for the entire industry. The ZenCash development team has proposed an enhancement to the Satoshi Consensus in order to prevent 51% attacks.

The longest chain rule, or Satoshi Consensus, worked well in the relatively decentralized environment in which it was introduced in 2009.  Mining resources have since concentrated and dropped in cost for lease, such that the original dominant strategy of playing by the rules no longer holds for all proof-of-work (PoW) blockchains that rely on the longest chain rule.  As recent events have proven, in some circumstances it can be economically feasible to launch 51% attacks on operational public blockchain networks.  This paper proposes a novel adjustment to Satoshi Consensus that makes it exponentially more costly, and hence unlikely, to launch such attacks for any proof-of-work mineable cryptocurrency system.