DIDComm v2

DIDComm v2 (formally "DIDComm Messaging") lets two software agents (a wallet, a bank's verifier service, an AI agent, anything holding a DID) exchange encrypted, authenticated messages with each other over whatever transport happens to be available, without a shared platform or vendor sitting in the middle to broker the conversation.

Ordinary messaging (email, a chat API, a webhook) ties the message to a specific transport and, usually, a specific provider's account system. DIDComm decouples the two: a message is built the same way, packed as an encrypted, signed envelope (a JWE) addressed to the recipient's DID, whether it then travels over HTTPS, gets embedded in a QR code, or rides over Bluetooth. The recipient's software unpacks it using keys tied to their own DID, the same way regardless of how the envelope arrived. That's what "transport-agnostic" buys: two agents built by two different vendors, on two different stacks, can talk as long as both speak DIDComm, no shared backend required.

On top of the base messaging layer, the ecosystem has built sub-protocols for specific jobs, establishing a connection via an "out-of-band" invitation, asking a third party to mediate/relay your messages while you're offline, picking up queued messages when you come back online. Those sub-protocols are what turn "encrypted envelopes" into an actual agent-to-agent messaging network.

Where it comes from

DIDComm v2 is a Decentralized Identity Foundation (DIF) specification, developed inside DIF's DIDComm Working Group after generalizing the earlier DIDComm v1 work that originated in the Hyperledger Aries community. It reached DIF's "Approved" status, the same bar Sidetree cleared, with the published spec crediting Sam Curren, Tobias Looker, Oliver Terbu, Kyle Den Hartog, and other working-group contributors as editors. Solidus designed none of the protocol and none of its envelope cryptography.

Solidus status

Solidus Relay (relay.solidus.network) is a live, deployed DIDComm v2 mediator: the "always-on hop" that holds encrypted messages for agents that aren't online at the same moment. It implements two DIDComm companion protocols: CoordinateMediation 2.0 (a wallet asks the relay to mediate; the relay grants or denies, and the wallet registers which keys should route to it) and Pickup Protocol 3.0 (the wallet later asks what's waiting, and pulls it down). Under the hood, the actual pack/unpack cryptography is handled by didcomm-node, a WASM library built by SICPA implementing the DIF spec, Solidus wrote the mediator service logic (the request/response state machine, keylists, queued delivery) on top of that library, not the envelope crypto itself.

This runs on Solidus's public testnet only, and neither didcomm-node nor Solidus's mediator code has had an independent security audit. It's also worth being clear about scope: Solidus implements DIDComm's mediator role, not a full DIDComm-native issuer/holder/verifier agent, Solidus's own credential issuance and presentation (BBS+, SD-JWT VC) run over a different protocol family, OpenID4VCI and OpenID4VP, not DIDComm. And the @solidus-network/relay package is not published to npm (npm view actually published to npm as of this writing (npm view @solidus-network/relay` returns a 404), there's a live service, not yet an installable SDK.

Proof you can run yourself: curl https://relay.solidus.network/invite returns a real DIDComm v2 out-of-band invitation: "type":"https://didcomm.org/out-of-band/2.0/invitation", a did:key sender, and a service block advertising "accept":["didcomm/v2"]. Any conformant DIDComm v2 agent, Credo-TS, Veramo, ACA-Py, can take that invitation and drive the mediation handshake against it without taking Solidus's word for any of it.