==== EIP 1820: Pseudo-introspection Registry Contract  ====
[[dido:public:ra:xapend:xapend.b_stds:defact:ethereum:eip| Return to Ethereum ERCs ]]

  : **Note**: The following is an excerpt from the official Ethereum site. It is provided here as a convenience and is not authoritative. Refer to the original document as the authoritative reference.

<table>
<caption>Data sheet for Pseudo-introspection Registry Contract</caption>
| Title                      | Pseudo-introspection Registry Contract |
| Author                     | Jordi Baylina, Jacques Dafflon |
| Status                     | Final |
| Created                    | 2019-03-04  |
| Description                | [[http://eips.ethereum.org/EIPS/eip-1820]] |
| Specification              | [[http://eips.ethereum.org/EIPS/eip-1820#Specification]] |
| Category                   | ERC |
| Requires                   | [[dido:public:ra:xapend:xapend.b_stds:defact:ethereum:eip:erc_0165|165 ]], [[dido:public:ra:xapend:xapend.b_stds:defact:ethereum:eip:erc_0214|214]]   |
| Replaces                   | [[ http://eips.ethereum.org/EIPS/eip-820 |ERC 820]] |
</table>

=== Simple Summary === 
  : //This standard defines a universal registry [[dido:public:ra:xapend:xapend.a_glossary:s:smart_contract|smart contract]] where any address (contract or regular account) can register which [[dido:public:ra:xapend:xapend.a_glossary:i:interface|interface]] it supports and which smart contract is responsible for its implementation.//

  : //This standard keeps backward compatibility with [[dido:public:ra:xapend:xapend.b_stds:defact:ethereum:eip:erc_0165| ERC165]].//

=== Abstract === 
  : //This standard defines a registry where smart contracts and regular accounts can publish which functionality they implement—either directly or through a proxy contract.//

  : //Anyone can query this registry to ask if a specific address implements a given interface and which smart contract handles its implementation.//

  : //This registry MAY be deployed on any chain and shares the same address on all chains.//

  : //Interfaces with zeroes (0) as the last 28 bytes are considered [[dido:public:ra:xapend:xapend.b_stds:defact:ethereum:eip:erc_0165|ERC165]] interfaces, and this registry SHALL forward the call to the contract to see if it implements the interface.//

  : //This contract also acts as an [[dido:public:ra:xapend:xapend.b_stds:defact:ethereum:eip:erc_0165|ERC165]] cache to reduce [[dido:public:ra:xapend:xapend.a_glossary:g:gas|gas]] consumption.//

=== Motivation === 
  : //There have been different approaches to define pseudo-introspection in [[dido:public:ra:xapend:xapend.a_glossary:e:ethereum|Ethereum]]. The first is [[dido:public:ra:xapend:xapend.b_stds:defact:ethereum:eip:erc_0165|ERC165]] which has the limitation that it cannot be used by regular accounts. The second attempt is [[ https://github.com/ethereum/EIPs/issues/672 |ERC672]] which uses reverse Ethereum Name Service (ENS)((
Ethereum Name Service, [[https://ens.domains/]]
)). Using reverse ENS has two issues. First, it is unnecessarily complicated, and second, ENS is still a centralized contract controlled by a ''multisig''. This ''multisig'' theoretically would be able to modify the system.//

  : //This standard is much simpler than ERC672, and it is fully decentralized.// \\ 

  : //This standard also provides a unique address for all chains. Thus solving the problem of resolving the correct registry address for different chains.//