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QIP-19: Confidential Assets #19

shannon1916 opened this issue Jun 7, 2019 · 0 comments


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commented Jun 7, 2019


This QIP would enable the implementation of confidential assets on Qtum.


Qtum is a public blockchain where all data, including transactions and contracts, are open and permanently stored in the blockchain. Although addresses are generated from random private keys, their links to user identities can be leaked from exchanges, merchants or even by collecting and clustering the blockchain data. This level of confidentiality is not enough for applying Qtum to some business scenarios.

There are several solutions proposed, like zk-SNARKs and MimbleWimble, to improve the confidentiality of blockchain. These solutions make significant changes to the blockchain system, so they are normally implemented on new blockchains instead of existing ones.

But recently, some projects are trying to use smart contracts to implement them on Ethereum, for example, AZTEC and Zether. These projects benefit from the precompiled contracts for elliptic-curve operations introduced by EIP-196, which make it possible to realize some core functions of the solutions in a relatively low gas cost. With these projects, users are able to issue confidential assets on Ethereum.

Whereas, gas costs for confidential assets are still very high. The cost of a confidential transfer is approximately 900k in AZTEC and 7188k in Zether, while a block’s gas limit is roughly 8000k. So they rely on some EIPs, like EIP-1108 and EIP-1109, to further reduce the gas cost. On the other hand, precompiled contracts of more elliptic-curve operations would be helpful to them.


Since Qtum supports EVM, AZTEC and Zether can be definitely ported to Qtum. The main work needs to do is to reduce their gas costs.


Something can be done to enable the implementation of confidential assets on Qtum.

  1. Run these projects on Qtum, analyzing actual gas costs for node resources.
  2. Reduce gas costs of precompiled contracts, like EIP-1108 and EIP-1109.
  3. Add new precompiled contracts for elliptic-curve operations, as should be further investigated.

@shannon1916 shannon1916 changed the title QIP-19: Confidential Assets QIP-19 Jun 7, 2019

@shannon1916 shannon1916 changed the title QIP-19 QIP-19: Confidential Assets Jun 7, 2019

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