Vade

About

Vade is a framework for working with VCs and DIDs from different providers and on different platforms in a constant manner. Even if the actual implementation and logic behind them may change, Vade offers a consistent interface to work with them. It has been developed with wasm support in mind to allow it not only to run on servers but also on different clients with limited resources like IoT devices.

The name "Vade" is an acronym for "VC and DID engine" and focuses on working with VCs and DIDs. It has been designed with the idea of offering a consistent interface to work with while supporting to move the actual work into plugins.

This library is currently under development. Behavior, as well as provided exports, may change over time.

Documentation about Vades functions and their meaning can be found here.

Plugins

Vade is relying on plugins to run interact provider specific logic. The current set of Plugins can be seen below:

DID plugins

Method	Info
did:evan
did:example	vade-example-plugin
(universal resolver method list)	in development

More coming soon. To write your own plugins, have a look at writing own plugins.

VC plugins

Method	Info
did:evan

More coming soon. To write your own plugins, have a look at writing own plugins.

Example Usage

use vade::Vade;
use some_crate:ExamplePlugin;
use vade::VadePlugin;
struct ExamplePlugin { }
impl ExamplePlugin { pub fn new() -> Self { ExamplePlugin {} } }
impl VadePlugin for ExamplePlugin {}

async fn example_vade_usage() {
    let ep: ExamplePlugin = ExamplePlugin::new();
    let mut vade = Vade::new();
    vade.register_plugin(Box::from(ep));

    match vade.did_create("did:example", "", "").await {
        Ok(results) => {
            let result = results[0].as_ref().unwrap().to_string();
            println!("created did: {}", result);
        },
        Err(e) => panic!(format!("could not create did; {}", e)),
    };
}

As you can see, an instance of ExamplePlugin is created and handed over to a Vade instance with register_plugin. To be a valid argument for this, ExamplePlugin needs to implement VadePlugin.

Vade delegates the call all functions with the same name as the functions of VadePlugin to all registered plugins, so the result of such calls is a Vec of optional String values (Vec<Option<String>>).

Basic Plugin Flow

Calls of plugin related functions follow the rule set described here:

• a Vade instance delegates all calls of plugin related functions to all registered plugins
• those VadePlugin instances then may or may not process the request
• requests may be ignored due to not being implemented or due to ignoring them due to plugin internal logic (e.g. if a did method is not supported by the plugin, requests for this method are usually ignored)
• ignored plugin requests do not end up in the result Vec, so a Vade may have registered multiple plugins, but if only on plugin caters to a certain did method, calls related to this method will only yield a single result

Vade Features

The current set of features can be grouped into 3 clusters:

• management functions
• DID interaction
• zero knowledge proof VC interaction

Management Functions

register_plugin

Registers a new plugin. See VadePlugin for details about how they work.

DID Interaction

did_create

Creates a new DID. May also persist a DID document for it, depending on plugin implementation.

did_resolve

Fetch data about a DID. This usually returns a DID document.

did_update

Updates data related to a DID. May also persist a DID document for it, depending on plugin implementation.

Zero Knowledge Proof VC Interaction

vc_zkp_create_credential_schema

Creates a new zero-knowledge proof credential schema. The schema specifies properties a credential includes, both optional and mandatory.

vc_zkp_create_credential_definition

Creates a new zero-knowledge proof credential definition. A credential definition holds cryptographic key material and is needed by an issuer to issue a credential, thus needs to be created before issuance. A credential definition is always bound to one credential schema.

vc_zkp_create_credential_proposal

Creates a new zero-knowledge proof credential proposal. This message is the first in the credential issuance flow.

vc_zkp_create_credential_offer

Creates a new zero-knowledge proof credential offer. This message is the response to a credential proposal.

vc_zkp_request_credential

Requests a credential. This message is the response to a credential offering.

vc_zkp_create_revocation_registry_definition

Creates a new revocation registry definition. The definition consists of a public and a private part. The public part holds the cryptographic material needed to create non-revocation proofs. The private part needs to reside with the registry owner and is used to revoke credentials.

vc_zkp_update_revocation_registry

Updates a revocation registry for a zero-knowledge proof. This step is necessary after revocation one or more credentials.

vc_zkp_issue_credential

Issues a new credential. This requires an issued schema, credential definition, an active revocation registry and a credential request message.

vc_zkp_revoke_credential

Revokes a credential. After revocation the published revocation registry needs to be updated with information returned by this function.

vc_zkp_request_proof

Requests a zero-knowledge proof for one or more credentials issued under one or more specific schemas.

vc_zkp_present_proof

Presents a proof for a zero-knowledge proof credential. A proof presentation is the response to a proof request.

vc_zkp_verify_proof

Verifies a one or multiple proofs sent in a proof presentation.

Custom Functions

run_custom_function

Calls a custom function. Plugins may subscribe to such custom calls, that are not part of the default set of Vades default feature set, which allows to add custom plugin logic while using `Vade. Examples for this may be connection handling and key generation.

Except for the management functions all functions will be delegated to plugins. Plugins handling follows the following rules:

• a Vade instance delegates all calls of plugin related functions to all registered plugins
• those VadePlugin instances then may or may not process the request
• requests may be ignored due to not being implemented or due to ignoring them due to plugin internal logic (e.g. if a did method is not supported by the plugin, requests for this method are usually ignored)
• ignored plugin requests do not end up in the result Vec, so a Vade may have registered multiple plugins, but if only on plugin caters to a certain did method, calls related to this method will only yield a single result

Writing own Plugins

Writing own plugin is rather simple, an example and details how to write them can be found in the VadePlugin documentation.

Wasm Support

Vade supports Wasm! ^^

For an example how to use Vade in Wasm and a how to guide, have a look at our vade-wasm-example project.