ASA Burning App

Abstract

This ARC provides TEAL which would deploy a application that can be used for burning Algorand Standard Assets. The goal is to have the apps deployed on the public networks using this TEAL to provide a standardized burn address and app ID.

Motivation

Currently there is no official way to burn ASAs. While one can currently deploy their own app or rekey an account holding the asset to some other address, having a standardized address for burned assets enables explorers and dapps to easily calculate and display burnt supply for any ASA burned here.

It is important to note that assets with clawback enabled are effectively impossible to “burn” and could at any point be clawed back from any account or contract. The definitions below attempt to clarify some terminology around tokens and what can be considered burned.

Token Type	Clawback	No Clawback
Total Supply	Total	Total
Circulating Supply	Total - Qty in Reserve Address - Qty in burn address	Total - Qty in Reserve Address - Qty in burn address
Available Supply	Total	Total - Qty in burn address
Burned Supply	N/A (Impossible to burn)	Qty in burn address

Specification

`ARC-4` JSON Description

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{
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  "name": "ARC54",
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  "desc": "Standardized application for burning ASAs",
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  "methods": [
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    {
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      "name": "arc54_optIntoASA",
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      "args": [
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        {
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          "name": "asa",
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          "type": "asset",
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          "desc": "The asset to which the contract will opt in"
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        }
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      ],
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      "desc": "A method to opt the contract into an ASA",
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      "returns": {
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        "type": "void",
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        "desc": ""
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      }
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    },
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    {
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      "name": "createApplication",
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      "desc": "",
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      "returns": {
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        "type": "void",
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        "desc": ""
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      },
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      "args": []
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    }
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  ]
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}

Rationale

This simple application is only able to opt in to ASAs but not send them. As such, once an ASA has been sent to the app address it is effectively burnt.

If the burned ASA does not have clawback enabled, it will remain permanently in this account and can be considered out of circulation.

The app will accept ASAs which have clawback enabled, but any such assets can never be considered permanently burned. Users may use the burning app as a convenient receptable to remove ASAs from their account rather than returning them to the creator account.

The app will, of course, only be able to opt into a new ASA if it has sufficient Algo balance to cover the increase minimum balance requirement (MBR). Callers should fund the contract account as needed to cover the opt-in requests. It is possible for the contract to be funded by donated Algo so that subsequent callers need not pay the MBR requirement to request new ASA opt-ins.

Reference Implementation

TEAL Approval Program

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#pragma version 9
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// This TEAL was generated by TEALScript v0.62.2
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// https://github.com/algorandfoundation/TEALScript
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// This contract is compliant with and/or implements the following ARCs: [ ARC4 ]
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// The following ten lines of TEAL handle initial program flow
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// This pattern is used to make it easy for anyone to parse the start of the program and determine if a specific action is allowed
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// Here, action refers to the OnComplete in combination with whether the app is being created or called
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// Every possible action for this contract is represented in the switch statement
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// If the action is not implemented in the contract, its respective branch will be "NOT_IMPLEMENTED" which just contains "err"
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txn ApplicationID
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int 0
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>
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int 6
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*
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txn OnCompletion
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+
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switch create_NoOp NOT_IMPLEMENTED NOT_IMPLEMENTED NOT_IMPLEMENTED NOT_IMPLEMENTED NOT_IMPLEMENTED call_NoOp
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NOT_IMPLEMENTED:
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  err
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// arc54_optIntoASA(asset)void
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//
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// /*
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// Sends an inner transaction to opt the contract account into an ASA.
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// The fee for the inner transaction must be covered by the caller.
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//
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// @param asa The ASA to opt in to
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abi_route_arc54_optIntoASA:
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  // asa: asset
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  txna ApplicationArgs 1
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  btoi
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  txnas Assets
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  // execute arc54_optIntoASA(asset)void
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  callsub arc54_optIntoASA
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  int 1
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  return
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arc54_optIntoASA:
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  proto 1 0
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  // contracts/arc54.algo.ts:13
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  // sendAssetTransfer({
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  //       assetReceiver: globals.currentApplicationAddress,
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  //       xferAsset: asa,
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  //       assetAmount: 0,
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  //       fee: 0,
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  //     })
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  itxn_begin
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  int axfer
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  itxn_field TypeEnum
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  // contracts/arc54.algo.ts:14
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  // assetReceiver: globals.currentApplicationAddress
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  global CurrentApplicationAddress
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  itxn_field AssetReceiver
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  // contracts/arc54.algo.ts:15
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  // xferAsset: asa
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  frame_dig -1 // asa: asset
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  itxn_field XferAsset
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  // contracts/arc54.algo.ts:16
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  // assetAmount: 0
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  int 0
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  itxn_field AssetAmount
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  // contracts/arc54.algo.ts:17
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  // fee: 0
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  int 0
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  itxn_field Fee
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  // Submit inner transaction
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  itxn_submit
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  retsub
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abi_route_createApplication:
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  int 1
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  return
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create_NoOp:
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  method "createApplication()void"
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  txna ApplicationArgs 0
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  match abi_route_createApplication
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  err
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call_NoOp:
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  method "arc54_optIntoASA(asset)void"
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  txna ApplicationArgs 0
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  match abi_route_arc54_optIntoASA
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  err

TealScript Source Code

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import { Contract } from '@algorandfoundation/tealscript';
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// eslint-disable-next-line no-unused-vars
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class ARC54 extends Contract {
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  /*
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   * Sends an inner transaction to opt the contract account into an ASA.
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   * The fee for the inner transaction must be covered by the caller.
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   *
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   * @param asa The ASA to opt in to
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   */
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  arc54_optIntoASA(asa: Asset): void {
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    sendAssetTransfer({
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      assetReceiver: globals.currentApplicationAddress,
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      xferAsset: asa,
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      assetAmount: 0,
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      fee: 0,
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    });
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  }
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}

Deployments

An application per the above reference implementation has been deployed to each of Algorand’s networks at these app IDs:

Network	App ID	Address
MainNet	1257620981	BNFIREKGRXEHCFOEQLTX3PU5SUCMRKDU7WHNBGZA4SXPW42OAHZBP7BPHY
TestNet	497806551	3TKF2GMZJ5VZ4BQVQGC72BJ63WFN4QBPU2EUD4NQYHFLC3NE5D7GXHXYOQ
BetaNet	2019020358	XRXCALSRDVUY2OQXWDYCRMHPCF346WKIV5JPAHXQ4MZADSROJGDIHZP7AI

Security Considerations

It should be noted that once an asset is sent to the contract there will be no way to recover the asset unless it has clawback enabled.

Due to the simplicity of a TEAL, an audit is not needed. The contract has no code paths which can send tokens, thus there is no concern of an exploit that undoes burning of ASAs without clawback.