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Media types for iden3comm protocol

Media type of message defines the format of the envelope that is used in messaging. More read at DIDComm specification.

Supported media types of envelope

  • application/iden3-zkp-json
  • application/iden3comm-plain-json
  • application/iden3comm-signed-json
  • application/iden3comm-encrypted-json

Each media type shows how envelope of the message is created and present in the payload as a typ field.

When to use:

  • application/iden3-zkp-json corresponds to jwz envelope about which you can read more here.
  • application/iden3comm-signed-json corresponds to JWS envelope.
  • application/iden3comm-plain-json represents simple json message with a property 'typ'.
  • application/iden3comm-encrypted-json is a media type for encrypted envelops

In our protocol corresponding packers are implemented in golang and typescript.

To determine which envelope to use, the sender can specify the accept header, allowing the responder to choose one of the supported profiles for authentication. Profile is a combination of media type and specific parameters for this media type.

For ZKP profile circuits param could be added (optional):

  • authV2

For ZKP, Signed and Encrypted profiles alg param could be added (optional)

ZKP profole params:

  • groth16

Signing algorithms:

  • ES256K
  • ES256K-R

Encryption algorimts:

  • anoncrypt ( ECDH-ES + AES key wrap; AES-CBC + HMAC-SHA512)

Currently accept header is only applicable for authorization request message. Possible example: 

[
  "iden3comm/v1;env=application/iden3-zkp-json;circuitId=authV2;alg=groth16",
  "iden3comm/v1;env=application/iden3comm-signed-json;alg=ES256K-R"
]

If accept header is omitted - default value is:

[
  "iden3comm/v1;env=application/iden3-zkp-json;circuitId=authV2;alg=groth16"
]

So default response will always use auth v2 circuit, groth 16 proof generator and jwz envelope.

In case user initiates a communication, for example with embedded issuer and doesn't know what kind of profiles issuer agent accepts it should use discovery protocol.