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   Achim Domma (achim@social.saarland)'s status on Sunday, 11-Jan-2026 06:17:09 JST Achim Domma

   I try to implement an #activitypub server in #Rust, have problems talking to #mastodon and would appreciate some help.

   I try to send a follow action to Mastodon. The request is - as far as I can tell - signed according to https://docs.joinmastodon.org/spec/security/

   The "keyId" of the signatrue is "https://pub.saar.social/user/achim/key". Mastodon calls this url as expected and my server returns: [...]

   • Embed this notice
     silverpill (silverpill@mitra.social)'s status on Sunday, 11-Jan-2026 06:17:06 JST silverpill

     in reply to

     @achim I don't know about Mastodon, but here are some general tips:

     - Your actor is served with content-type application/json, but it should be application/ld+json; profile="https://www.w3.org/ns/activitystreams"
     - It's better to embed the key in your actor document and identify it with a fragment ID. This is more widely supported than standalone keys.

   • Embed this notice
     Achim Domma (achim@social.saarland)'s status on Sunday, 11-Jan-2026 06:17:07 JST Achim Domma

     in reply to

     [...]

     {
     "@context":["https://www.w3.org/ns/activitystreams","https://w3id.org/security/v1"],
     "id":"https://pub.saar.social/user/achim/key",
     "type":"Key",
     "publicKeyPem":"-----BEGIN PUBLIC KEY-----\nMIIBI[...]IDAQAB\n-----END PUBLIC KEY-----\n",
     "owner":"https://pub.saar.social/user/achim"
     }

     But my follow http call gets this back from Mastodon:

     {"error":"Unable to fetch key JSON at https://pub.saar.social/user/achim/key"}

     Can somebody give me a hint how to figure out what the problem is?

   • Embed this notice
     silverpill (silverpill@mitra.social)'s status on Sunday, 11-Jan-2026 07:00:43 JST silverpill

     in reply to

     @achim Lemmy is also in Rust! And there are two Rust libraries:

     - https://docs.rs/activitypub_federation/latest/activitypub_federation/ (from Lemmy devs)
     - https://docs.rs/apx_sdk/latest/apx_sdk/ (this one is developed by me)

   • Embed this notice
     Achim Domma (achim@social.saarland)'s status on Sunday, 11-Jan-2026 07:00:45 JST Achim Domma

     in reply to

     • silverpill

     @silverpill Thanks! Mitra looks very interesting. I'll have a look and will probably pop up in your Matrix channel. I was not aware that there is a maintained ActivityPub project in Rust.