Pull request for this CIP draft is at:
https://github.com/cardano-foundation/CIPs/pull/319
Abstract
This Cardano Improvement Proposal (CIP) specifies a process, by which a relation between Cardano addresses and Domain Name System (DNS) domains can be established. Such a relation can be used in both directions: Wallet apps can allow to discover addresses based on given domains and they can also annotate given addresses with domains found for them.
Motivation
Different proposals have been made to, on one hand, increase the confidence that the receive address is the correct one when sending transactions, on the other hand, make discovery and input of addresses in wallet apps easier.
For example, ADA Handles can be used in some wallet apps instead of an address. adadomains.io is another project with a similar goal. But these solutions are not decentralised and depend on the projects behind them continuing their work.
This CIP proposes a decentralised process for relating Cardano addresses to DNS domains and validating these relations in both directions. This relates Cardano addresses to the established identities of projects, organisations, and companies given by the domains they own and manage.
Moreover, the tokens used to define the relation from addresses to domains can be minted by the owners of the addresses themselves. This leaves the full control of the process with these owners and does not give it to commercial entities, which may or may not continue to operate and may or may not exploit a monopolistic position regarding the provision of identities for addresses on the Cardano blockchain.
Specification
Domain Tokens
In the direction from a Cardano address to a DNS domain, the relation is established by Cardano native tokens with an asset name of Domain (446f6d61696e as hexadecimal bytes) and metadata attached to them in their minting transactions.
These tokens are meant to be minted by the owner of the address(es) and the domain(s) – or someone acting on their behalf. Therefore, they will have varying policy IDs and they are to be found only by the asset name.
Like, for example, in CIP 25, only the metadata attached to the latest minting transaction for the same combination of policy ID and asset name must be considered, so that it can be overwritten by newer minting transactions – even without sending the token to the target address(es).
If, however, Domain tokens with different policy IDs are found at an address, the metadata found for all of them, must be taken into account.
The domain tokens are only used as containers for or pointers to data – the domain names – in this CIP. They do not convey ownership of the domain and anyone can mint a token claiming a connection to any domain. It is the purpose of the validation in later sections to ensure the truth of these claims.
This also means that it doesn’t necessarily make sense to use time-locked or even Plutus policies for them. A policy with only constraints on the public key hash(es) is probably enough, but this CIP does not prohibit more complicated policies.
Domain Token Metadata
The transaction_metadatum_label for the DNS domains recorded in the metadata of Domain tokens shall be registered as 53 (the standard port number of DNS):
| transaction_metadatum_label | description |
|---|---|
| 53 | DNS Domain |
The metadatum at this label is the domain that is represented by this token – either as a single UTF-8 string or as an array of strings, in JSON representation:
{ "53": "example.org" }
or
{ "53": [ "very.long.subdomain.for.",
"example.org" ] }
Since strings in the metadata of Cardano transactions are restricted to 64 bytes, the domain has to be split into such an array of strings if it is longer than 64 bytes.
The domain must be a DNS domain name as specified in RFC 1034 and following. For internationalised domain names as specified in RFC 5890 and following, the Punycode encoding of RFC 3492 has to be used.
DNS Validation
The first method for establishing the relation in the opposite direction – from a DNS domain to Cardano addresses – is realised by TXT records in DNS itself as specified in RFC 1035.
We use TXT records at _addresses._cardano. subdomains such as, for example, _addresses._cardano.example.org. Using an underscore _ at the beginning of a subdomain for such special purposes to avoid clashes with subdomains used for other purposes is a well-known technique used by a lot of network standards. The _addresses. subsubdomain is used to allow other processes and CIPs to later also use _cardano. for other purposes.
Each TXT record contains exactly one Cardano address without any additional content. Since the DNS allows multiple TXT records for a (sub)domain, we can relate an arbitrary number of addresses with a domain with this approach.
HTTP(S) Validation
The second method for establishing the relation from a DNS domain to Cardano addresses is realised by JSON documents that can be obtained from well-known URIs as specified in RFC 8615.
The files should be obtainable from the path /.well-known/cardano/addresses.json at the domain.
This leads, for example, to the URLs http://example.org/.well-known/cardano/addresses.json and https://example.org/.well-known/cardano/addreses.json. If HTTPS is available on the web server (it should be), the HTTP URL may, but does not have to be a redirect to the HTTPS URL.
The JSON document at this URL has the following structure:
[ { "address": "addr1…",
"Comment": "<Purpose of this address>" },
{ "address": "addr1…",
"Comment": "<Purpose of this address>" } ]
It is a list of JSON objects, which must have an "address" field and may have arbitrary additional fields.
Discovery and Verification of Relations
A wallet app or other tool that discovers and verifies relations between Cardano addresses and DNS domains must proceed as follows:
If a Cardano address is given:
- Find all domains related to it by
Domaintokens as given below. - For all of these domains, find all addresses related to them by DNS and/or HTTP(S) as given below.
- The result are all domains that point back to the given address.
- Domains not pointing back to the given address must be ignored.
If a DNS Domain is given:
- Find all addresses related to it by DNS and/or HTTP(S) as given below.
- For all of these addresses, find all domains related to them by
Domaintokens as given below. - The result are all addresses that point back to the given domain.
- Addresses not pointing back to the given domain must be ignored.
For a Cardano address, all related domains are found by:
- All tokens with an asset name of
Domain(446f6d61696e) that are currently at an unspent transaction output (UTxO) of that address are searched. - For these tokens, the latest minting transaction with associated metadata is determined.
- For these minting transactions, the respective domain in the metadata is added to the set of related domains.
For a DNS domain, all related addresses are found by:
- A DNS query for TXT records at the subdomain
_addresses._cardanoof the given domain is made. If TXT records are found, all addresses in these records are considered DNS-related addresses. - A HTTP(S) request is made to the path
/.well-known/cardano/addresses.jsonat the given domain. If a JSON file is obtained, all addresses given in this JSON file are considered HTTP(S)-related addresses. - If both methods are used, the intersection of HTTP(S)-related addresses and DNS-related addresses is the set of related addresses. If only one method is used, its result is the set of related addresses. If none of the methods is used, the set of related addresses is empty.
Observe that if at least one TXT record for the DNS method or a JSON file for the HTTP(S) method is found, the method is considered to be used even if the content of the TXT record is not a valid address or the JSON file is malformed
If the relation is established in both directions, applications can give a rating to the verification, for example, one star for DNS, one for HTTP, and one for HTTPS for a maximum of three stars.
If possible, applications should give all related domains for a given address and all related addresses for a given domain and allow to choose between them where appropriate.
Applications can display additional metadata given in the JSON files obtained by the HTTP(S) validation method.
In order to avoid stalling the application when many domain tokens are found at an address, implementations should do the queries asynchronously or concurrently if possible.
Rationale
Simplicity
At most decision points, we have opted for simplicity to encourage as many projects, organisations, and people as possible to adopt this without the need for exceptional expertise to implement it.
The Domain tokens contain just the domain name of one domain as a string and nothing more, which reduces the space needed on-chain for these metadata (and the transaction fees for minting the tokens). If multiple domains are needed, the owner can easily mint Domain tokens under different policies to achieve this.
The information in the TXT records of the DNS validation method are just the addresses and nothing more.
Only the JSON files of the HTTP(S) validation method contain additional metadata. These can, in most cases, be modified most easily. Thus, it is sensible to have additional metadata at this place.
Scalability
Businesses like exchanges or shops often use customer-specific receive addresses. Validating all of them by the process of this CIP could lead to very large sets of related addresses for the main domain.
An easy way to handle this is to use subdomains to group related addresses, for example by purpose, customer group, individual customers, or by time.
Organisations can also choose to only validate their main addresses used over an extended period of time by both methods, while the additional addresses are only validated by HTTP(S) (on a different subdomain, so that the requirement is still fulfilled that DNS- and HTTP(S)-related addresses coincide), where the management can easily be automated through standard server-side web programming methods.
Security
The process validates that the person who decides to mint and/or send a token containing a DNS domain name to a specific Cardano address also controls the DNS and/or HTTP(S) server for that domain.
Proving the control of a domain by TXT records in DNS and by resources at a /.well-known path over HTTP(S) is used and considered sufficient in a lot of successful protocols and applications:
- Let’s Encrypt use both techniques in their Automatic Certificate Management Environment, specified in RFC 8555, to ascertain that a domain is controlled by a server and a TLS certificate can be issued for it.
- Sender Policy Framework (SPF), specified in RFC 7208, DomainKeys Identified Mail (DKIM), specified in RFC 6376, and Domain-based Message Authentication, Reporting, and Conformance (DMARC), specified in RFC 7489, are standards for validating mail origins, which all use TXT records in DNS to give authoritative information about the policies of a domain regarding mail originating from that domain.
- As further examples, Google and dnswl.org also use TXT records to validate control of a domain.
Unsolicited Domain Tokens
A third party could mint a token with an unrelated domain and send it to an address in an unsolicited transaction. If this third party also controls the DNS/HTTP(S) servers of that domain, they could also achieve the validation process being successful.
Additional methods to remedy this, for example signatures by all claimed addresses on the token or its minting transaction, would have sacrificed too much of the simplicity of the approach. Existing projects like ADA Handle also do not remedy unsolicited sending of identifiers to an address.
The risk is acceptable, since the critical use case is the other direction: A user wants to send to a specific project, organisation, or shop, for which the domain is known and validate that the address belongs to it. And this use case is not affected by unsolicited tokens, but only by attackers gaining control over the DNS/HTTP(S) servers of the project, organisation, or shop.
Sending an unsolicited Domain token can only redirect transactions that people wanted to send to the domain controlled by the attacker to the receiver of the unsolicited token, which does not seem to be a very sensible attack vector.
A small risk remains that the receiver of the token may be defamed by the attacker’s domain appearing next to the receiver’s legitimate domains, when an application shows all validated domains for an address.
Moreover, the attacker’s servers could deliberately stall answers to the DNS and especially HTTP(S) queries done for the validation. This problem can to a large extent be attacked by implementations that do the queries asynchronously or concurrently as already advised in Discovery and Verification of Relations.
Address owners should monitor such unsolicited transactions and send such tokens to unused addresses or back to the sender.
Reference Implementation and Example
A reference implementation of the processes described in Discovery and Verification of Relations can be found in the accompanying Python script cardano-domain-validation.py. For the queries to the Cardano blockchain, it uses koios.rest.
Example Preparation
We use two example domains – the author’s domains bbraatz.eu and heptasean.de – that have been configured for domain validation as specified in this CIP:
$ dig _addresses._cardano.bbraatz.eu TXT
_addresses._cardano.bbraatz.eu. 3600 IN TXT "addr1q8fgal6mmwdllxdvft28xy6x3wjgc3v6nj450smmhtdama6wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ysjatmn5"
_addresses._cardano.bbraatz.eu. 3600 IN TXT "addr1q9wvykt8vpvgrqjr9lgm8d9dstgl3h2wesdrqlxa4gqdv62wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ysv6v74x"
_addresses._cardano.bbraatz.eu. 3600 IN TXT "Not an address"
$ curl https://bbraatz.eu/.well-known/cardano/addresses.json
[ { "address": "addr1q8fgal6mmwdllxdvft28xy6x3wjgc3v6nj450smmhtdama6wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ysjatmn5" },
{ "address": "addr1q8fe7mx9xdpr063tkp8k5r65psy9p469az04rh86epcaxz2wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ys3ufz2q" },
{ "address": "Not an address" } ]
For this domain, we have information in DNS as well as in JSON via HTTPS. One address – addr1…jatmn5 – is in both, while one is only in DNS and one only in the JSON file. The latter two should be ignored by implementations, since DNS and HTTP(S) validation have to coincide. The entries that are not addresses should also be ignored.
$ dig _addresses._cardano.heptasean.de TXT
$ curl https://heptasean.de/.well-known/cardano/addresses.json
[ { "address": "addr1q8fgal6mmwdllxdvft28xy6x3wjgc3v6nj450smmhtdama6wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ysjatmn5",
"Comment": "Main Wallet" },
{ "address": "addr1qyh72hvvrurjvddx4gq37jd2fzyef8scz9cwcyc90dffq0xxllh3nc5r82ujj36fy9zh0gryqvqy7r3ejd2h2kgsvryswhjr9q",
"Comment": "Token Trading" },
{ "address": "addr1qyjwqxz8sry4ul522x5zfp4na2t5m4qkuxtpzw0tll99a8zwlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0yscp2j47",
"Comment": "No Domain token" } ]
For this domain, we do not have information in DNS, but only in JSON via HTTPS. This should be accepted by implementations, but result in a lower rating. The JSON file makes use of the additional keys to give comments for addresses. Two addresses – addr1…jatmn5, already configured for the other domain, and addr1…whjr9q – will be valid, while the third will not get a corresponding domain token and should, hence, be ignored by implementations.
We find Domain tokens for our example domains at the corresponding example addresses:
$ curl "https://api.koios.rest/api/v0/address_assets?_address=addr1qyh72hvvrurjvddx4gq37jd2fzyef8scz9cwcyc90dffq0xxllh3nc5r82ujj36fy9zh0gryqvqy7r3ejd2h2kgsvryswhjr9q&asset_name=eq.446f6d61696e"
[ { "policy_id": "2ca754177885f5c0431e38d216a26ded1e35aa3a6d6dd163ffd41417",
"asset_name": "446f6d61696e",
"quantity": "1" } ]
$ curl "https://api.koios.rest/api/v0/asset_info?_asset_policy=2ca754177885f5c0431e38d216a26ded1e35aa3a6d6dd163ffd41417&_asset_name=446f6d61696e&select=minting_tx_metadata"
[ { "minting_tx_metadata":
[ { "key": "53",
"json": "heptasean.de" },
{ "key": "721",
"json":
{ "2ca754177885f5c0431e38d216a26ded1e35aa3a6d6dd163ffd41417":
{ "Domain":
{ "name": "Domain: heptasean.de",
"image": […] } } } } ] } ]
Since this address is only connected to the second domain heptasean.de, we only find one token there for that same domain. As you can see, there are also standard NFT metadata included, so that the domain token can be identified (and looks nice) in wallet apps not supporting this present CIP. This is not required by this specification, though.
$ curl "https://api.koios.rest/api/v0/address_assets?_address=addr1q8fgal6mmwdllxdvft28xy6x3wjgc3v6nj450smmhtdama6wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ysjatmn5&asset_name=eq.446f6d61696e"
[ { "policy_id": "4f2aebe9413c5b7b461aa9faa47e5a0664dfc0d3d7d33f1576d775bb",
"asset_name": "446f6d61696e",
"quantity": "1" },
{ "policy_id": "9dc5bc52956b0aae62a40ab0628951fb26cf3ebc27fdfe849b1fa142",
"asset_name": "446f6d61696e",
"quantity": "1" },
{ "policy_id": "2ca754177885f5c0431e38d216a26ded1e35aa3a6d6dd163ffd41417",
"asset_name": "446f6d61696e",
"quantity": "1" } ]
$ curl "https://api.koios.rest/api/v0/asset_info?_asset_policy=4f2aebe9413c5b7b461aa9faa47e5a0664dfc0d3d7d33f1576d775bb&_asset_name=446f6d61696e&select=minting_tx_metadata"
[ { "minting_tx_metadata":
[ { "key": "53",
"json": "bbraatz.eu" },
{ "key": "721",
"json":
{ "4f2aebe9413c5b7b461aa9faa47e5a0664dfc0d3d7d33f1576d775bb":
{ "Domain":
{ "name": "Domain: bbraatz.eu",
"image": […] } } } } ] } ]
On this address, we find three Domain tokens. The first token represents the connection to the first domain bbraatz.eu.
$ curl "https://api.koios.rest/api/v0/asset_info?_asset_policy=9dc5bc52956b0aae62a40ab0628951fb26cf3ebc27fdfe849b1fa142&_asset_name=446f6d61696e&select=minting_tx_metadata"
[ { "minting_tx_metadata":
[ { "key": "53",
"json": "example.com" },
{ "key": "721",
"json":
{ "9dc5bc52956b0aae62a40ab0628951fb26cf3ebc27fdfe849b1fa142":
{ "Domain":
{ "name": "Domain: example.com",
"image": […] } } } } ] } ]
The second token claims that this address also belongs to the domain example.com, but on that domain we will neither find a DNS nor a HTTP(S) validation, so that implementations should ultimately ignore it.
$ curl "https://api.koios.rest/api/v0/asset_history?_asset_policy=2ca754177885f5c0431e38d216a26ded1e35aa3a6d6dd163ffd41417&_asset_name=446f6d61696e&select=minting_txs"
[ { "minting_txs":
[ { "tx_hash": "8ef972221023f0c78dfa31c480e48f3a344beb633319e49e72ddf6823a48e36f",
"block_time": 1660482520,
"quantity": "1",
"metadata":
[ { "key": "53",
"json": "heptasean.de" },
{ "key": "721",
"json":
{ "2ca754177885f5c0431e38d216a26ded1e35aa3a6d6dd163ffd41417":
{ "Domain":
{ "name": "Domain: heptasean.de",
"image": […] } } } } ] },
{ "tx_hash": "a2d246cc72682900d264478e82d3ce4aeb35a01683699744f6043791d95d8a88",
"block_time": 1660482379,
"quantity": "1",
"metadata":
[ { "key": "53",
"json": "example.org" },
{ "key": "721",
"json":
{ "2ca754177885f5c0431e38d216a26ded1e35aa3a6d6dd163ffd41417":
{ "Domain":
{ "name": "Domain: example.org",
"image": […] } } } } ] } ] } ]
We have already seen the third token on the other address addr1…whjr9q. Looking at the minting history, we can see that both instances were minted with different transactions, where the later transaction changed their metadata to the one we see now, pointing to the domain heptasean.de. The first minted token (which incidentally was the one sent to addr1…whjr9q) originally pointed to the domain example.org. Neither CIP 25 nor this CIP care about the concrete transaction history of a specific instance of a token, but give the metadata in the latest minting transaction for any token with that combination of policy ID and asset name, which is also what the Koios API will give us by default.
Example in Reference Implementation
When executing the reference implementation on our example domains, we get:
$ python3 cardano-domain-validation.py bbraatz.eu
★★★ addr1q8fgal6mmwdllxdvft28xy6x3wjgc3v6nj450smmhtdama6wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ysjatmn5
For the first domain – bbraatz.eu – it gives us the only configured address – addr1…jatmn5 – with a rating of 3/3, since both DNS and HTTPS are used to validate. The addresses only present in one of the methods are ignored just as the non-address contents are.
$ python3 cardano-domain-validation.py heptasean.de
★★☆ addr1q8fgal6mmwdllxdvft28xy6x3wjgc3v6nj450smmhtdama6wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ysjatmn5
Comment: Main Wallet
★★☆ addr1qyh72hvvrurjvddx4gq37jd2fzyef8scz9cwcyc90dffq0xxllh3nc5r82ujj36fy9zh0gryqvqy7r3ejd2h2kgsvryswhjr9q
Comment: Token Trading
For the second domain – heptasean.de – it gives us both configured addresses with the additional comments given as metdata for them and a rating of 2/3, since we have not used DNS validation for these. The third address in the JSON file is ignored, because no domain token is found at it.
Vice versa, when executing the implementation for our example addresses, we get:
$ python3 cardano-domain-validation.py addr1qyh72hvvrurjvddx4gq37jd2fzyef8scz9cwcyc90dffq0xxllh3nc5r82ujj36fy9zh0gryqvqy7r3ejd2h2kgsvryswhjr9q
★★☆ heptasean.de
Comment: Token Trading
For the first address – addr1…whjr9q – we only get the second domain linked to it with its comment and rating.
$ python3 cardano-domain-validation.py addr1q8fgal6mmwdllxdvft28xy6x3wjgc3v6nj450smmhtdama6wlu8vnqcstwtxa4l3yuckm8gttva66skvfzrmruead0ysjatmn5
★★★ bbraatz.eu
★★☆ heptasean.de
Comment: Main Wallet
For the second address – addr1…jatmn5 – it gives us both domains with their different ratings and the additional comment metadata for the second one. The third token found at that address is ignored, because neither DNS nor HTTP(S) method find any data pointing back at example.com.
Path to Active
Usage
In order for this CIP to become active, it should be implemented by relevant wallet apps and Cardano blockchain explorers and be used by relevant projects and/or organisations to validate their addresses.
Registrations
The transaction_metadatum_label 53 from the section Domain Token Metadata has to be registered in the registry according to CIP 0010.
The well-known URI /.well-known/cardano from the section HTTP Validation has to be registered according to RFC 8615. This registration can also be reused for other CIPs that need data at a well-known location on a web server.
Backwards Compatibility
Since this is a newly proposed process, there are no backwards compatibility issues.
Copyright
This CIP is licensed under CC-BY-4.0.
)
. Especially if someone makes template Plutus contracts for it to mint, burn and transfer. Also, how feasible would it be for this token to be held in Plutus contract and still point to correct address?