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LibraryMarkets2022Design paperCorpus record

Refundable Fungible Token

ERC 5528. StartfundInc.

ERC 5528, Refundable Fungible Token. This specification defines a type of escrow service with the following flow: - The seller issues tokens.

Status in the source: Final. A reading of the public specification, not a copy of it and not a certification.

Refundable Fungible Token is worth reading for the rule it actually adds: This specification defines a type of escrow service with the following flow: - The seller issues tokens.

The five-minute read

The rule

This specification defines a type of escrow service with the following flow: - The seller issues tokens.

What was already failing

A token that each contract invents from scratch does not transfer, approve, or display in any other contract. The cost of a shared interface is that the interface's holes become everyone's holes.

What the number does not mean

The source marks this final. That is a statement about the text, not a promise that every wallet or node has shipped it.

What a builder should be able to point at

An implementation either constrains MUST or it is a different design.

One action, walked through

  1. Open ERC 5528 and read the status line before the examples.
  2. Write down the rule in one sentence. A fair version of that sentence is: This specification defines a type of escrow service with the following flow: - The seller issues tokens.
  3. Name the object that changes: MUST.
  4. Ask what an old client, an old contract, or an offline counterparty does. If the document is silent, the silence is part of the design.

The argument, unpacked

What the text is allowed to settle

Ethereum Request for Comment 5528 can settle the shape of Refundable Fungible Token. It cannot settle whether a later client, a later fork, or a later wallet still does this.

What this page will not pretend

There is no benchmark, no adoption number, and no claim that the mechanism is safe outside the assumptions written in the source.

What has to be true

  • You are implementing ERC 5528 at the status the text itself states: Final.
  • The object that has to change is MUST. A neighbouring document with a similar name is not this one.
  • The standard does not enforce royalties, identity, or a price. If the transfer function does not check it, the chain will not.

What happened after the paper

The source marks this final. That is a statement about the text, not a promise that every wallet or node has shipped it. Later documents can narrow, replace, or ignore this one. Cite the number you mean.

What to check before you use the idea

  • Which function in Refundable Fungible Token actually moves or approves value?
  • What happens on a callback, a zero amount, or a contract recipient that rejects?
  • Which names does the text commit to: MUST?

Terms

ERC 5528
The public text titled Refundable Fungible Token.
Final
The document's own label for how finished the text is. It is not a market fact.

The problem the paper names

A token that each contract invents from scratch does not transfer, approve, or display in any other contract. The cost of a shared interface is that the interface's holes become everyone's holes.

What the design proposes

  • This specification defines a type of escrow service with the following flow: - The seller issues tokens.
  • The seller creates an escrow smart contract with detailed escrow information like contract addresses, lock period, exchange rate, additional escrow success conditions, etc.
  • The seller funds seller tokens to the Escrow Contract.

How the mechanism is specified

  • Taken from the specification, the next constraint is: The seller creates an escrow smart contract with detailed escrow information like contract addresses, lock period, exchange rate, additional escrow success conditions, etc.
  • Locate MUST in ERC 5528 and apply it to one transaction or call.
  • Then check the failure the class of rule always has: a node that did not upgrade, a reverted call, a replayed signature, or a peer that does not speak the message.

What this page does not treat as proven

  • An application standard is not consensus. A contract can ignore it and still be a valid account.
  • The standard does not enforce royalties, identity, or a price. If the transfer function does not check it, the chain will not.
  • The source marks this final. That is a statement about the text, not a promise that every wallet or node has shipped it.

Why a venture studio still reads it

Use ERC 5528 when a pitch says 'Refundable Fungible Token' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.

This is Blockchain Lab's reading of a public design paper. It is not the paper, not a copy of it, and not an offer of tokens, equity, custody or a partnership. Later network behaviour can diverge from the text. Nothing here is investment, legal or technical advice.

Research status: Design paper. Last reviewed: 1 October 2026. This is a reading of a public paper, not investment, legal or security advice.