Kohei Tanaka
Jul 30 · 3 min read


We designed the Passer Contract and Distributor Contract for 0x protocol ecosystem.The BlockBase Team has developed two extension contracts that enable projects to offer new forms of NFT trading to their users.

Who we are?

BlockBase, Inc. is a development and consulting firm of blockchain technology based in Japan. And we build Marketplace of NFT which named bazaaar. 3 months ago, we were adopted by Acceleration program of 0x. Therefore we replaced backend system to 0x protocol and built new 0x Extensions contracts for Japanese regulation and a better UX.

Passer Contract

Wrapping ETH into ERC-20 compliant wETH has been a barrier to adoption for the greater DeFi ecosystem. With the Passer Contract, users can simply send ETH and the orders they want to fill. It is similar to a forwarder contract, but the passer contract that the taker to send ETH and get ETH to the maker.

The algorithm of passer contract is temporarily mint and approve PASS tokens(ERC20) when the fill order is executed. Then PASS token and ERC721 token are transferred by ERC20Proxy and ERC721Proxy. When PASS token TransferFrom is called, the minted passer token is burned and ETH is automatically send to the maker. These processes is executed in one single transaction. Please refer to this image for details of the transaction.

Passer tokens are like a gear. It is for the smooth sending and receiving of ETH.More information of the Passer Contract can be found here.

Distributor Contract

In the current 0x Protocol system, although the fee payment was ZRX, the users needs to get ZRX tokens, We need to improve usability more easily. It is also discussed in ZEIPs.
The distributor contract allows taker and maker fees to be paid in ETH.The developer and the service provider set the fee distribution address and distribution ratio, and the distributor contract enables distribution. The distribution is possible up to 10 or more addresses because it is made with emphasis on extensibility. This also enables the return of profits to developers and creators who provide NFT. More information of the Distributor Contract can be found here.


We are confident that we can contribute to the 0x ecosystem. This contracts has already been released (Apache License 2.0). A library using this contract will be provided as an open source soon.We deliver NFT developers much easier and simpler way to build MarketPlace of NFT!


プロトコルやチェーンと既存のビジネスの間に立ち、 プロダクトのプロトタイピングを高速且つ大量に繰り返し 本当に有用なblockchainのユースケースを探し続ける

Thanks to KentaroYamamura and BlockBase

Kohei Tanaka

Written by

BlockBase,Inc | Blockchain Engineer



プロトコルやチェーンと既存のビジネスの間に立ち、 プロダクトのプロトタイピングを高速且つ大量に繰り返し 本当に有用なblockchainのユースケースを探し続ける

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