Building out Incognito’s trustless bridge to Bitcoin and all other blockchains

What privacy problem are you solving?

Today, anyone can send BTC, ETH, and thousands of other cryptocurrencies to another party without going through a financial institution. For those who value privacy, these cryptocurrencies come with a big tradeoff. Transactions are recorded on public ledgers, displaying amounts involved, inscribing virtual identities of their senders and receivers. Given the choice, we strongly believe that very few people will willingly disclose their crypto financials to the entire world.

The inherent lack of privacy to cryptonetworks today is a real and present threat to the entire crypto space.

What is the solution?

We’re proposing a solution to shield any cryptocurrency – BTC, ETH, USDT, etc. In effect, any cryptocurrency can now be a privacy coin. Both shielding and unshielding processes are carried out via a decentralized group of trustless custodians. Once shielded, transactions are confidential and untraceable.

Shielding is the process of turning cryptocurrencies on other cryptonetworks (or “public coins”) into privacy coins on Incognito. Through Portal, a public coin can be shielded to obtain its privacy coin counterpart of the same value. For example, BTC can be shielded to obtain the privacy coin pBTC. pBTC has the same value as BTC, so 1 pBTC can always be redeemed for 1 BTC and vice versa.

Once shielded, privacy coin transactions are confidential and untraceable. A privacy coin enjoys the best of both worlds. It retains the value of its original counterpart and can be transacted confidentially on the Incognito network


Figure 1. Shielding BTC and minting pBTC. Other public coins follow the same shielding process. Note that we simplify step 5 to make it simple for readers to follow the main logic: the proof of deposit is not generated by the custodian, but by the miners of underlying cryptonetwork.

Unshielding is the reverse process of shielding: turning privacy coins back into public coins


Figure 2. Unshielding pBTC and releasing BTC. Other public coins follow the same unshielding process

What substitutes do people resort to because this doesn’t exist yet?

Current blockchain interoperability solutions mostly involve building ad-hoc bridges. BTC Relay, WBTC, and TBTC build ad hoc bridges between Bitcoin and Ethereum, while Kyber Network builds Waterloo, an ad hoc bridge between Ethereum and EOS. For Portal, doing it ad hoc – one bridge for every cryptonetwork – is not a scalable option.

Portal takes a different approach: build once, work with any cryptonetwork. The shielding mechanism operates via a general bridge design that connects Incognito to any number of cryptonetworks, allowing for secure bi-directional transfers of cryptocurrencies whenever privacy is needed. This means any coin can now be a privacy coin. This approach is especially helpful for creating interoperability with cryptonetworks that do not support smart contracts, like Bitcoin and Binance Chain.

Who are you?

The project will be implemented by @duc, @hiennguyen, and @hoang on the core team.

  • @duc is the engineer of Incognito’s interoperability team. He’s been with the project since the beginning, leading the design and implementation of the Ethereum bridge (see Incognito mode for Ethereum). Previously, @duc worked on data engineering, AI, and scalable systems. His first crypto project was on decentralizing data sets for machine learning.

  • @hiennguyen is an engineer in Incognito’s interoperability team. She joined Incognito at the very beginning. Previously, @hiennguyen worked on cryptography and has now implemented the privacy protocol for Incognito. She is looking forward to increasing her knowledge and experience by moving on and helping to build out the Portal project.

  • @hoang recently joined Incognito’s interoperability team to help build cool stuff. Previously, @hoang worked for one of the biggest e-commerce systems in Vietnam called Tiki. He has had experiences with the popular programming languages as well as messaging systems like Kafka in a microservices architecture. He’s strongly interested in building scalable and reliable systems with low latency APIs. On a less serious note, as a human, he’d love to sleep well at night by building monitoring systems apart from the main system.

Why do you care?

Monero, Zcash, and Grin introduced their own version of cryptocurrencies that focus on privacy. Portal takes a different approach, based on the premise that people don’t want a new cryptocurrency with privacy. What they really want is privacy for their existing cryptocurrencies: incognito mode for any cryptocurrency.

Portal is designed so users don’t have to choose between their favorite cryptocurrencies and privacy coins. They can have both. They can hold any cryptocurrency and still be able to use it confidentially whenever they want. Privacy needs to be ubiquitous, inclusive, and accessible.

For these reasons, Portal is a really challenging project that is and worth solving, and we’re excited to make it happen.

What’s your plan? What’s your schedule?

The project duration will be 2 months from Feb 1, 2020 to May 31, 2020.

Ship Date Deliverable
March 31, 2020 Ship trustless bridge with Bitcoin, Binance Chain (Incognito bond contract) for Protocol side
April 30, 2020 Ship trustless bridge with Bitcoin, Binance Chain (Incognito bond contract) for App side
May 31, 2020 Ship trustless bridge with Bitcoin (Ethereum bond contract) for both Protocol and App

What’s your budget?

The project will be undertaken by 3 engineers for 4 months:

Resource Quantity Monthly Cost
Incognito protocol engineer 3 3,000 PRV
TOTAL (x 4 months) 12,000 PRV

Is there an existing conversation around this idea?

A few months ago, we received a grant from Binance that took the development of Portal to this point, and will help offset additional development costs going forward. See Binance funds development of the Incognito Portal for more details.

Is there anything else you would like the community to know?

We are always happy to hear feedback from the community so feel free to leave comments if any. Thanks.


Quick update for Feb 2020:

  • Finished up the development for shielding process
  • We’re now writing unit-tests for cases of the process. It’ll be done by the end of Feb 2020.
  • Next week, we’ll be starting working on unshielding process.

@duc HI👋
I hope you remember I asked you to take me as one of the first lucky ones custodians?


“end of Feb 2020” = tomorrow :slight_smile:

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sure @zes333, you’re one of the most active members on the forum. we’re actually appreciated… as the plan, we’ll be delivering the first version of the bridge at the end of March (Incognito bond contract) so can’t wait to see you there.


yep @abduraman, we’re working hard to get the shielding process done internally on our local environment. Really excited to be able to ship the first version of the bridge by the end of March.


@duc the update looks good. Funds for Feb has been disbursed, please kindly check.
We will continue disburse every subsequent week dependent on progress, so keep us updated.


Update: week of March 2 - 6, 2020:

  • We’ve been working on the redeem flow of Portal (a.k.a, pTokens -> public coins). It’s almost done, we’re still on testing for the flow.
  • The thing left of development is the auto-liquidate process (before going to the testing stage)
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Updates for the week of March 9 - 15, 2020:
We’ve been working on 3 things:

  • Incentives for custodians - custodians will receive shield mining rewards in addition to shielding fees (100%)
  • Auto-liquidation - that happens when custodian doesn’t return public coins (eg, bnb, btc) to user or value of bonded collaterals drops significantly (95%, a few issues just came up and we’re fixing them)
  • Bitcoin SPV processes - Apart from Binance chain (that has been implemented already), we’re also getting Bitcoin supported in Portal. For more details, we’ve been working on header relaying as well as transaction verification with Merkle tree processes for a week now (~60%). These are expected to be done next week.

Updates for the week of March 16 - 22, 2020:

  • We’ve almost done the implementation of this proposal. However, from the core team, there are some other proposals that are being worked in parallel. One of them is Reduce Blockchain size by 50%. The work of this proposal is really cool when it’s introducing a new way to store chain’s data much more efficiently. Unfortunately, the data of trustless bridge (aka Portal) is storing & manipulating in the old way which is not 100% compatible with the new way so we need to merge code and rework on that a bit next week.
  • For that reason, we’re proposing an extension of the protocol ship date for the first version until April 10 (instead of March 31 as planned). Really apologized about this.

@duc i personally think delaying it just 10 days but being able to ship both trustless bridge to bitcoin and blockchain size reduction to 50% is totally awesome! :rocket: :rocket: :rocket:


I think this is make sense for our system. Last week, I reviewed pull request code from Db version 2, and we have a lot of thing which be changed. This is newest code branch for dev, in here. Maybe your team need to have 2-3 days to merge back your branch, and retest again from this.

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Updates for the week of March 23 - 29, 2020:

  • We’ve finished merging code and upgrading Portal persistence to one that’s completely compatible with Database V2 (see it here: Reduce Blockchain size by 50%)
  • So the implementation of Portal for both Bitcoin and Binance chain has been done and we’ll be focusing on testing (eg., writing unit tests or even automation tests) next week.
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Early, @duc, to make this feature can come to user,
I think we need to make it with another proposal for UI/UX on app

Updates for the week of March 30 - April 5, 2020:

  • We’ve worked on 3 backend workers that are getting external information (eg., block headers from Bitcoin, Binance chain and coin prices from Coinmarketcap) and feeding into Incognito chain for further processes. The code of these workers could be found here (
  • We’ve also been working on testing for a while and will be continuing to focus on it next week. If everything’s going to be okay, we’ll deploy the protocol to mainnet by the end of next week.
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