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AsyDNS (Asymmetric Cryptography DNS)

My task in this world is provide DNS names to all the people that has an Asymmetric Cryptography Key Pair

I can give you awesome names like:

Ok, maybe not an "awesome name", but a really dynamic name.

What do you need?

  1. Generate a public/private key pair
  2. Claim your subdomain
  3. Probe (cryptographically) that you have the private key of the key pair
  4. Done! You have an AsyDNS subdomain! :)

The API it's really simple, and a Python 3.x client it's included with the package, just:

$ python3

The client generates a new RSA key pair, and claims your new domain name.

By default, we use, but you can host your own AsyDNS server with your own domain.

The development of this software is supported by Securetia SRL (

How to use (clients)



A reference implementation resides in this repo, at

Habu contains a client (habu.asydns)


The newest client is written in Go, and is multiplatform, is the recommended implementation:


If you know other implementations or you're interested in develop a new one, please, tell me and I will add a reference.

Usage Demo Video

Technical Details

The AsyDNS protocol it's really simple, but you need some cryptography background to understand it:

First, you need to have an RSA key pair. This will be used to sign your requests.

Second, you need to make an HTTP GET request to the AsyDNS server (default:

You will receive a challenge, that you need to sign with your private key.

Third, you need to make an HTTP POST request to the AsyDNS server, with the following:

  • The challenge that you've received on the GET request
  • The signed challenge (that you've signed with your private key)
  • Your public key

If the signature can be verified, the AsyDNS will create/update a record that will be:


That record will point to your public IP address.

Now, you can query that registry using the DNS protocol, like this:

$ dig +short

Also, you can revoke the registry (you need the private key to do that).

The process to revoke a registry it's equal to the process described to create a record, with only one modification: instead of a POST request, you need to make a DELETE HTTP request.

When a registry it's revoked, never will be valid. But, you can simply create a new RSA key pair and request another registry.

Backend Change on 2019-02-06

Today, I've changed the structure of AsyDNS to support various "backends". Those backends provide the functionality to react to the HTTP requests and update some DNS server.

The default backend (the only one generated for now) stores the information via Amazon Route53 API.

The past version of AsyDNS stored the information in the local filesystem, and this information was server throuhg the asydns-dnsd service. That service never was stable, so, has been removed.

Now, AsyDNS only serves the HTTP REST API. The DNS part is server through Amazon Route53.

From the client side, all the things works as before, because the HTTP REST API is exactly the same.

Frequently Asked Questions (FAQ)

¿Why I need that protocol?

Maybe, you don't need AsyDNS. But can be useful if you need to mantain a DNS record of your current public IP (or the public IP for a device that you manage).

In some form, it's like other Dynamic DNS services, but you don't need to registry an user, you only need an RSA key pair, that can be generated with standard tools, like OpenSSL.

¿Why do you use SHA224 for hashing?

Because the hexdigest of SHA224 can be used has a subdomain name. MD5 it's broken, and SHA256, SHA512, etc, generates a long hexdigest that is invalid has a subdomain name.

It's a stable proyect?

No, has been released on 5th April 2018.

Can I deploy my own AsyDNS server?

Of course, the repo includes a Fabric FabFile ( to deploy an OpenBSD instance with the server ready. You only need to configure the domain name that you will use.

If you want to deploy AsyDNS on other platforms, you can contact me and I can help you.

How can I contribute to the project?

You can use Github for that. Issues, pull requests, etc...


Asymmetric Cryptography DNS (AsyDNS)




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