I saw a dapp using Decentralized approach for the buying and selling ERC20 Tokens ..But there's no proof of using the functions defined in smart contract in the web3js library.How is that possible ?..What am I missing here??

I know, Smart contract code is on etherscan..Another scenario is, The Dapp take notes of the users data and authorized them based on their credentials..I don't see any code related user structure in web3js nor solidity...Instead they use PHP with a form to check if the credentials match..but they do use Metamask or Trust Wallet..So is it centralized or decentralized approach or combination of both.. is it possible to do so??

  • while performing any action on this dapp, do you receive metamask popup for confirmation of transaction? It would be helpful if you could share the link for the dapp. Commented Nov 1, 2020 at 14:15
  • They do not have any registeration fees..So whenever I register through their Dapp, Metamask pops up and ask me to connect my wallet to the dapp..But when I want to buy their ERC20 Token, Metamask pops up and ask for eth Commented Nov 1, 2020 at 14:17
  • Please provide the dapp link Commented Nov 1, 2020 at 14:19
  • Sure, dttexchange.com Commented Nov 1, 2020 at 14:20

1 Answer 1


So this dapp here.

For sure this a dapp. So what is happening:

  1. Click on register: Dapp requests user for account access via Metamask, where user have to confirm so that Dapp can move forward.

  2. Once you have Registered, on the dashboard you see the smart contract address to which it is interacting i.e. "0x7abE2a84368af480fFd4Beb7676133C30F37DC05" and your selected address on right hand side. Please refer to snapshot below.

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  1. Now you can buy some tokens by submitting a transaction via metamask, metamask popup does appear for the confirmation. Due to some error tx didnt succeed in my case.

  2. Once Tx succeed, you can lookup that transaction on contract page.

Few things, since it didnt ask for any personal information, any KYC, its a non-custodial dapp where complete control over the funds and token is with user.

Rest how much logging are they doing behind the scene over their server not sure about that. You can check those things from developer tab and see if any request is being sent to any other application server, and what data is sent.

Hope this helps.

  • Hi, thank you for your time..I wanna know where do they get to know, is the user already registered in their Dapp or not..because, I didn't see any code related user storage in solidity nor smart contract..so, is it possibility that they are using Centralized approach for storing user data Commented Nov 1, 2020 at 15:00
  • Yes, for registration purpose they are storing the ethereum address with them. Reason I am sure about this is because it doesnt ask transaction confirmation when you login. Also I am connected to Rinkeby testnet and still I am able to register my address though the contract mentioned in the dashboard in not present on Rinkeby net. Commented Nov 1, 2020 at 15:18

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