HashCash 2.0

HashCash is a Crypto-economic protocol to have better public communication tools.

The problem HashCash 2.0 solves

Generally any open public communication forum created by an individual is always spammed by people. E-mail service is the most abused. It forces people whose time is valuable to not check their inbox because it has a million emails with only a handful of them as useful to the individual. This spoils things for people who want to reach this individual for geneuine purposes and totally spoils the purpose of having an email account.

We want to make these public communication tools spam resistant and using economics bubble up things that matter to the individual


  • Reduce spam
  • Ability to priortise emails by urgency
  • Ability to buy attention of important people
  • Creating personal economies


  • VC’s for receiving pitch decks
  • People who get a lot of emails. For eg: those who use superhuman email client
  • Hiring process
  • General people to reduce spam and to never miss an important email
  • Ability to priortise emails by urgency
  • Ability to buy attention of important people
  • Creating personal economies

HOW IT WORKS (Personal Tokens)

  1. Sender(Alice) and Reciever(Bob) both have created a hashcash2.0 account.
  2. Alice buys $BOB from uniswap and sends an email to Bob with X $BOB tokens attached to it.
  3. As soon as the email hits Bob, he starts a reverse stream sending Alice her precious $BOB back at a predefined rate "r" defined by the amount and the duration of stream.
  4. As the email sits on the inbox it keeps on losing $BOB, this forces the receiver to respond to emails as soon as possible.
  5. Now if this is amongst the top emails by value that Bob has, he will see this email on the top and then if the email is spammy he can burn the amount remaining in the email, or he can choose to refund the amount, or he can choose a ratio between both.
  6. If the email was spam the burnt amount will decrease the total supply thus increasing the value of remaining $BOB i.e rewarding all token holders.
  7. As $BOB gets used more and more, the token holders are

Challenges we ran into

Amidst the lockdown our brainstorming sessions were through the means of video calls and we divided our work accordingly.

There were intial problems in integrating the smart contract as the different steps required validation and setting up the reverse stream was a difficult task to accomplish.

Another hurdle we came were setting up a email service in the application. We tried to setup our own SMTP server to have full control of the email headers and content to inject the contract details during sending of email but that was a difficult task to accompalish. So we stuck with using a central database to build the Proof of Concept.