Identity Management

On-ledger identity management focuses on the distributed aspect of identities across Canton system entities, while user identity management focuses on individual participants managing access of their users to their ledger APIs.

Canton comes with a built in identity management system used to manage on-ledger identities. The technical details are explained in the architecture section, while this write up here is meant to give a high level explanation.

The identity management system is self-contained and built without a trusted central entity or pre-defined root certificate such that anyone can connect with anyone, without the need of some central approval and without the danger of losing self-sovereignty.

Introduction

What is a Canton Identity?

When two system entities such as a participant, domain topology manager, mediator or sequencer communicate with each other, they will use asymmetric cryptography to encrypt messages and sign message contents such that only the recipient can decrypt the content, verify the authenticity of the message, or prove its origin. Therefore, we need a method to uniquely identify the system entities and a way to associate encryption and signing keys with them.

On top of that, Canton uses the contract language Daml, which represents contract ownership and rights through parties. But parties are not primary members of the Canton synchronisation protocol. They are represented by participants and therefore we need to uniquely identify parties and relate them to participants, such that a participant can represent several parties (and in Canton, a party can be represented by several participants).

Unique Identifier

A Canton identity is built out of two components: a random string X and a fingerprint of a public key N. This combination, (X,N), is called a unique identifier and is assumed to be globally unique by design. This unique identifier is used in Canton to refer to particular parties, participants or domain entities. A system entity (such as a party) is described by the combination of role (party, participant, mediator, sequencer, domain topology manager) and its unique identifier.

The system entities require knowledge about the keys which will be used for encryption and signing by the respective other entities. This knowledge is distributed and therefore, the system entities require a way to verify that a certain association of an entity with a key is correct and valid. This is the purpose of the fingerprint of a public key in the unique identifier, which is referred to as Namespace. And the secret key of the corresponding namespace acts as the root of trust for that particular namespace, as explained later.

Topology Transactions

In order to remain flexible and be able to change keys and cryptographic algorithms, we don’t identify the entities using a single static key, but we need a way to dynamically associate participants or domain entities with keys and parties with participants. We do this through topology transactions.

A topology transaction establishes a certain association of a unique identifier with either a key or a relationship with another identifier. There are several different types of topology transactions. The most general one is the OwnerToKeyMapping, which as the name says, associates a key with a unique identifier. Such a topology transaction will inform all other system entities that a certain system entity is using a specific key for a specific purpose, such as participant Alice of namespace 12345.. is using the key identified through the fingerprint AABBCCDDEE.. to sign messages.

Now, this poses two questions: who authorizes these transactions, and who distributes them?

For the authorization, we need to look at the second part of the unique identifier, the Namespace. A topology transaction that refers to a particular unique identifier operates on that namespace and we require that such a topology transaction is authorized by the corresponding secret key through a cryptographic signature of the serialised topology transaction. This authorization can be either direct, if it is signed by the secret key of the namespace, or indirect, if it is signed by a delegated key. In order to delegate the signing right to another key, there are other topology transactions of type NamespaceDelegation or IdentifierDelegation that allow one to do that. A namespace delegation delegates entire namespaces to a certain key, such as saying the key identifier through the fingerprint AABBCCDDEE… is now allowed to authorize topology transactions within the namespace of the key VVWWXXYYZZ…. An identifier delegation delegates authority over a certain identifier to a key, which means that the delegation key can only authorize topology transactions that act on a specific identifier and not the entire namespace.

Now, signing of topology transactions happens in a TopologyManager. Canton has many topology managers. In fact, every participant node and every domain have topology managers with exactly the same functional capabilities, just different impact. They can create new keys, new namespaces and the identity of new participants, parties and even domains. And they can export these topology transactions such that they can be imported at another topology manager. This allows to manage Canton identities in quite a wide range of ways. A participant can operate their own topology manager which allows them individually to manage their parties. Or they can associate themselves with another topology manager and let them manage the parties that they represent or keys they use. Or something in between, depending on the introduced delegations and associations.

The difference between the domain topology manager and the participant topology manager is that the domain topology manager establishes the valid topology state in a particular domain by distributing topology transactions in a way that every domain member ends up with the same topology state. However, the domain topology manager is just a gate keeper of the domain that decides who is let in and who not on that particular domain, but the actual topology statements originate from various sources. As such, the domain topology manager can only block the distribution, but cannot fake topology transactions.

The participant topology manager only manages an isolated topology state. However, there is a dispatcher attached to this particular topology manager that attempts to register locally registered identities with remote domains, by sending them to the domain topology managers, who then decide on whether they want to include them or not.

The careful reader will have noted that the described identity system indeed does not have a single root of trust or decision maker on who is part of the overall system or not. But also that the topology state for the distributed synchronisation varies from domain to domain, allowing very flexible topologies and setups.

Life of a Party

In the tutorials, we use the participant.parties.enable("name") function to setup a party on a participant. To understand the identity management system in Canton, it helps to look at the steps under the hood of how a new party is added:

  1. The participant.parties.enable function determines the unique identifier of the participant: participant.id.
  2. The party name is built as name::<namespace>, where the namespace is the one of the participant.
  3. A new party to participant mapping is authorized on the Admin Api: participant.topology.party_to_participant_mappings.authorize(...)
  4. The ParticipantTopologyManager gets invoked by the GRPC request, creating a new SignedTopologyTransaction and tests whether the authorization can be added to the local topology state. If it can, the new topology transaction is added to the store.
  5. The ParticipantTopologyDispatcher picks up the new transaction and requests the addition on all domains via the RegisterTopologyTransactionRequest message sent to the topology manager through the sequencer.
  6. A domain receives this request and processes it according to the policy (open or permissioned). The default setting is open.
  7. If approved, the request service attempts to add the new topology transaction to the DomainTopologyManager.
  8. The DomainTopologyManager checks whether the new topology transaction can be added to the domain topology state. If yes, it gets written to the local topology store.
  9. The DomainTopologyDispatcher picks up the new transaction and sends it to all participants (and back to itself) through the sequencer.
  10. The sequencer timestamps the transaction and embeds it into the transaction stream.
  11. The participants receive the transaction, verify the integrity and correctness against the topology state and add it to the state with the timestamp of the sequencer, such that everyone has a synchronous topology state.

Note that the participant.parties.enable macro only works if the participant controls their namespace themselves, either directly by having the namespace key or through delegation (via NamespaceDelegation).

Participant Onboarding

Key to support topological flexibility is that participants can easily be added to new domains. Therefore, the on-boarding of new participants to domains needs to be secure but convenient. Looking at the console command, we note that in most examples, we are using the connect command to connect a participant to a domain. The connect command just wraps a set of admin-api commands:

val certificates = OptionUtil.emptyStringAsNone(certificatesPath).map { path =>
  BinaryFileUtil.readByteStringFromFile(path) match {
    case Left(err) => throw new IllegalArgumentException(s"failed to load ${path}: ${err}")
    case Right(bs) => bs
  }
}
DomainConnectionConfig.grpc(
  domainAlias,
  connection,
  manualConnect,
  domainId,
  certificates,
  priority,
  initialRetryDelay,
  maxRetryDelay,
  timeTrackerConfig,
)

// register the domain configuration
register(config.copy(manualConnect = true))
if (!config.manualConnect) {
  // fetch and confirm domain agreement
  config.sequencerConnection match {
    case _: GrpcSequencerConnection =>
      confirm_agreement(config.domain.unwrap)
    case _ => ()
  }
  reconnect(config.domain.unwrap, retry = false).discard
  // now update the domain settings to auto-connect
  modify(config.domain.unwrap, _.copy(manualConnect = false))
}

We note that from a user perspective, all that needs to happen by default is to provide the connection information and accepting the terms of service (if required by the domain) to set up a new domain connection. There is no separate on-boarding step performed, no giant certificate signing exercise happens, everything is set up during the first connection attempt. However, quite a few steps happen behind the scenes. Therefore, we briefly summarise the process here step by step:

  1. The administrator of an existing participant needs to invoke the domains.register command to add a new domain. The mandatory arguments are a domain alias (used internally to refer to a particular connection) and the sequencer connection URL (http or https) including an optional port http[s]://hostname[:port]/path. Optional are a certificates path for a custom TLS certificate chain (otherwise the default jre root certificates are used) and the domain id of a domain. The domain id is the unique identifier of the domain that can be defined to prevent man-in-the-middle attacks (very similar to an ssh key fingerprint).
  2. The participant opens a GRPC channel to the SequencerConnectService.
  3. The participant contacts the SequencerConnectService and checks if using the domain requires signing specific terms of services. If required, the terms of service are displayed to the user and an approval is locally stored at the participant for later. If approved, the participant attempts to connect to the sequencer.
  4. The participant verifies that the remote domain is running a protocol version compatible with the participant’s version using the SequencerConnectService.handshake. If the participant runs an incompatible protocol version, the connection will fail.
  5. The participant will download and verify the domain id from the domain. The domain id can be used to verify the correct authorization of the topology transactions of the domain entities. If the domain id has been provided previously during the domains.register call (or in a previous session), the two ids will be compared. If they are not equal, the connection will fail. If the domain id was not provided during the domains.register call, the participant will use and store the one downloaded. We assume here that the domain id is obtained by the participant through a secure channel such that it is sure to be talking to the right domain. Therefore, this secure channel can be either something happening outside of Canton or can be provided by TLS during the first time we contact a domain.
  6. The participant downloads the static domain parameters, which are the parameters used for the transaction protocol on the particular domain, such as the cryptographic keys supported on this domain.
  7. The participant connects to the sequencer initially as an unauthenticated member. Such members can only send transactions to the domain topology manager. The participant then sends an initial set of topology transactions required to identify the participant and define the keys used by the participant to the DomainTopologyManagerRequestService. The request service inspects the validity of the transactions and decides based on the configured domain on-boarding policy. The currently supported policies are open (default) and permissioned. While open is convenient for permissionless systems and for development, it will accept any new participant and any topology transaction. The permissioned policy will accept the participant’s onboarding transactions only if the participant has been added to the allow-list beforehand.
  8. The request service forwards the transactions to the domain topology manager, who attempts to add it to the state (and thus trigger the distribution to the other members on a domain). The result of the onboarding request is sent to the unauthenticated member who disconnects upon receiving the response.
  9. If the onboarding request is approved, the participant now attempts to connect to the sequencer as the actual participant.
  10. Once the participant is properly enabled on the domain and its signing key is known, the participant can subscribe to the SequencerService with its identity. In order to do that and in order to verify the authorisation of any action on the SequencerService, the participant requires to obtain an authorization token from the domain. For this purpose, the participant requests a Challenge from the domain. The domain will provide it with a nonce and the fingerprint of the key to be used for authentication. The participant signs this nonce (together with the domain id) using the corresponding private key. The reason for the fingerprint is simple: the participant needs to sign the token using the participants signing key as defined by the domain topology state. However, as the participant will learn the true domain topology state only by reading from the SequencerService, it cannot know what the key is. Therefore, the domain discloses this part of the domain topology state as part of the authorisation challenge.
  11. Using the created authentication token, the participant starts to use the SequencerService. On the domain side, the domain verifies the authenticity and validity of the token by verifying that the token is the expected one and is signed by the participant’s signing key. The token is used to authenticate every GRPC invocation and needs to be renewed regularly.
  12. The participant sets up the ParticipantTopologyDispatcher, which is the process that tries to push all topology transactions created at the participant node’s topology manager to the domain topology manager. If the participant is using its topology manager to manage its identity on its own, these transactions contain all the information about the registered parties or supported packages.
  13. As mentioned above, the first set of messages received by the participant through the sequencer will contain the domain topology state, which includes the signing keys of the domain entities. These messages are signed by the sequencer and topology manager and are self-consistent. If the participants know the domain id, they can verify that they are talking to the expected domain and that the keys of the domain entities have been authorized by the owner of the key governing the domain id.
  14. Once the initial topology transactions have been read, the participant is ready to process transactions and send commands.
  15. When a participant is (re-)enabled, the domain topology dispatcher analyses the set of topology transactions the participant has missed before. It sends these transactions to the participant via the sequencer, before publicly enabling the participant. Therefore, when the participant starts to read messages from the sequencer, the initially received messages will be the topology state of the domain.

Default Initialization

The default initialization behaviour of participant and domain nodes is to run their own topology manager. This provides a convenient, automatic way to configure the nodes and make them usable without manual intervention, but it can be turned off by setting the auto-init = false configuration option before the first startup.

During the auto initialization, the following steps will happen:

  1. On the domain, we generate four signing keys: one for the namespace and one each for the sequencer, mediator and topology manager. On the participant, we generate three keys: a namespace key, a signing key and an encryption key.
  2. Using the fingerprint of the namespace, we generate the participant identity. For understandability, we use the node name used in the configuration file. This will change into a random identifier for privacy reasons. Once we’ve generated it, we set it using the set_id admin-api call.
  3. We create a root certificate as NamespaceDelegation using the namespace key, signing with the namespace key.
  4. Then, we create an OwnerToKeyMapping for the participant or domain entities.

The init.identity object can be set to control the behavior of the auto initialization. For instance, it is possible to control the identifier name that will be given to the node during the initialization. There are 3 possible configurations:

  1. Use the node name as the node identifier
canton.participants.participant1.init.identity.node-identifier.type = config
  1. Explicitly set a name
canton.participants.participant1.init.identity.node-identifier.type = explicit
canton.participants.participant1.init.identity.node-identifier.name = MyName
  1. Generate a random name
canton.participants.participant1.init.identity.node-identifier.type = random

Identity Setup Guide

As explained, Canton nodes auto-initialise themselves by default, running their own topology managers. This is convenient for development and prototyping. Actual deployments require more care and therefore, this section should serve as a brief guideline.

Canton topology managers have one crucial task they must not fail at: do not lose access to or control of the root of trust (namespace keys). Any other key problem can somehow be recovered by revoking an old key and issuing a new owner to key association. Therefore, it is advisable that participants and parties are associated with a namespace managed by a topology manager that has sufficient operational setups to guarantee the security and integrity of the namespace.

Therefore, a participant or domain can

  1. Run their own topology manager with their identity namespace key as part of the participant node.
  2. Run their own topology manager on a detached computer in a self-built setup that exports topology transactions and transports them to the respective node (i.e. via burned CD roms).
  3. Ask a trusted topology manager to issue a set of identifiers within the trusted topology manager’s namespace as delegations and import the delegations to the local participant topology manager.
  4. Let a trusted topology manager manage all the topology state on-behalf.

Obviously, there are more combinations and options possible, but these options here describe some common options with different security and recoverability options.

In order to reduce the risk of losing namespace keys, additional keys can be created and allowed to operate on a certain namespace. In fact, we recommend doing this and avoid storing the root key on a live node.

User Identity Management

So far we have covered how on-ledger identities are managed.

Every participant also needs to manage access to their local Ledger API and be able to give applications permission to read or write to that API on behalf of parties. While an on-ledger identity is represented as a party, an application on the Ledger API is represented and managed as a user. A ledger API server manages applications’ identities through:

  • authentication: recognizing which user an application corresponds to (essentially by matching an application name with a user name)
  • authorization: knowing which rights an authenticated user has and restricting their Ledger API access according to those rights

Authentication is based on JWT and covered in the application development / authorization section of the manual; the related Ledger API authorization configuration is covered in the Ledger API JWT configuration section.

Authorization is managed by the Ledger API’s User Management Service. In essence, a user is a mapping from a user name to a set of parties with read or write permissions. In more detail a user consists of:

  • a user id (also called user name)
  • an active/deactivated status (can be used to temporarily ban a user from accessing the Ledger API)
  • an optional primary party (indicates which party to use by default when submitting a Ledger API command requests as this user)
  • a set of user rights (describes whether a user has access to the admin portion of the Ledger API and what parties this user can act or read as)
  • a set of custom annotations (string based key-value pairs, stored locally on the Ledger API server, that can be used to attach extra information to this party, e.g. how it relates to some business entity)

All these properties except the user id can be modified. To learn more about annotations refer to the Ledger API Reference documentation . For an overview of the ledger API’s UserManagementService, see this section.

You can manage users through the Canton console user management commands, an alpha feature. See the cookbook below for some concrete examples of how to manage users.

Cookbook

Manage Users

In this section, we present how you can manage participant users using the Canton console commands. First, we create three parties that we’ll use in subsequent examples:

@ val (alice, bob, eve) = (participant1.parties.enable("alice"), participant1.parties.enable("bob"), participant1.parties.enable("eve"))
(alice, bob, eve) : (PartyId, PartyId, PartyId) = (alice::12201b97b185..., bob::12201b97b185..., eve::12201b97b185...)

Create

Next, create a user called myuser with act-as alice and read-as bob permissions and active user status. This user’s primary party is alice. The user is not an administrator and has some custom annotations.

@ val user = participant1.ledger_api.users.create(id = "myuser", actAs = Set(alice.toLf), readAs = Set(bob.toLf), primaryParty = Some(alice.toLf), participantAdmin = false, isActive = true, annotations = Map("foo" -> "bar", "description" -> "This is a description"))
user : User = User(
  id = "myuser",
  primaryParty = Some(
    value = "alice::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769"
  ),
  isActive = true,
  annotations = Map("foo" -> "bar", "description" -> "This is a description")
)

There are some restrictions for what constitutes a valid annotation key. In contrast, the only constraint for annotation values is that they must not be empty. To learn more about annotations refer to the Ledger API Reference documentation.

Update

You can update a user’s primary party, active/deactivated status and annotations. (You can also change what rights a user has, but using a different method presented further below.)

In the following snippet, you change the user’s primary party to be unassigned, leave the active/deactivated status intact, and update the annotations. In the annotations, you change the value of the description key, remove the foo key and add the new baz key. The return value contains the updated state of the user:

@ val updatedUser = participant1.ledger_api.users.update(id = user.id, modifier = user => { user.copy(primaryParty = None, annotations = user.annotations.updated("description", "This is a new description").removed("foo").updated("baz", "bar")) })
updatedUser : User = User(
  id = "myuser",
  primaryParty = None,
  isActive = true,
  annotations = Map("baz" -> "bar", "description" -> "This is a new description")
)

Inspect

You can fetch the current state of the user as follows:

@ participant1.ledger_api.users.get(user.id)
res4: User = User(
  id = "myuser",
  primaryParty = None,
  isActive = true,
  annotations = Map("baz" -> "bar", "description" -> "This is a new description")
)

You can query what rights a user has:

@ participant1.ledger_api.users.rights.list(user.id)
res5: UserRights = UserRights(
  actAs = Set("alice::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769"),
  readAs = Set("bob::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769"),
  participantAdmin = false
)

You can grant more rights. The returned value contains only newly granted rights; it does not contain rights the user already had even if you attempted to grant them again (like the read-as alice right in this example):

@ participant1.ledger_api.users.rights.grant(id = user.id, actAs = Set(alice.toLf, bob.toLf), readAs = Set(eve.toLf), participantAdmin = true)
res6: UserRights = UserRights(
  actAs = Set("bob::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769"),
  readAs = Set("eve::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769"),
  participantAdmin = true
)

You can revoke rights from the user. Again, the returned value contains only rights that were actually removed:

@ participant1.ledger_api.users.rights.revoke(id = user.id, actAs = Set(bob.toLf), readAs = Set(alice.toLf), participantAdmin = true)
res7: UserRights = UserRights(
  actAs = Set("bob::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769"),
  readAs = Set(),
  participantAdmin = true
)

Now that you have granted and revoked some rights, you can fetch all of the user’s rights again and see what they are:

@ participant1.ledger_api.users.rights.list(user.id)
res8: UserRights = UserRights(
  actAs = Set("alice::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769"),
  readAs = Set(
    "bob::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769",
    "eve::12201b97b185811c24790399fb62bff3daa2b15f5e772a4957c0226cb89ccc013769"
  ),
  participantAdmin = false
)

Also, multiple users can be fetched at the same time. In order to do that, first create another user called myotheruser and then list all the users whose user name starts with my:

@ participant1.ledger_api.users.create(id = "myotheruser")
res9: User = User(id = "myotheruser", primaryParty = None, isActive = true, annotations = Map())

@ participant1.ledger_api.users.list(filterUser = "my")
res10: UsersPage = UsersPage(
  users = Vector(
    User(id = "myotheruser", primaryParty = None, isActive = true, annotations = Map()),
    User(
      id = "myuser",
      primaryParty = None,
      isActive = true,
      annotations = Map("baz" -> "bar", "description" -> "This is a new description")
    )
  ),
  nextPageToken = ""
)

Decommission

You can delete a user by its id:

@ participant1.ledger_api.users.delete("myotheruser")

You can confirm it has been removed by e.g. listing it:

@ participant1.ledger_api.users.list("myotheruser")
res12: UsersPage = UsersPage(users = Vector(), nextPageToken = "")

If you want to prevent a user from accessing the ledger API it may be better to deactivate it rather than deleting it. A deleted user can be recreated as if it never existed in the first place, while a deactivated user must be explicitly reactivated to be able to access the ledger API again.

@ participant1.ledger_api.users.update("myuser", user => user.copy(isActive = false))
res13: User = User(
  id = "myuser",
  primaryParty = None,
  isActive = false,
  annotations = Map("baz" -> "bar", "description" -> "This is a new description")
)

Adding a new Party to a Participant

The simplest operation is adding a new party to a participant. For this, we add it normally at the topology manager of the participant, which in the default case is part of the participant node. There is a simple macro to enable the party on a given participant if the participant is running their own topology manager:

val name = "Gottlieb"
participant1.parties.enable(name)

This will create a new party in the namespace of the participants topology manager.

And there is the corresponding disable macro:

participant1.parties.disable(name)

The macros themselves just use topology.party_to_participant_mappings.authorize to create the new party, but add some convenience such as automatically determining the parameters for the authorize call.

Note

Please note that the participant.parties.enable macro will add the parties to the same namespace as the participant is in. It only works if the participant has authority over that namespace either by possessing the root or a delegated key.

Important

This feature is only available in Canton Enterprise

Migrate Party to Another Participant Node

Parties are only weakly tied to participant nodes. They can be allocated in their own namespace and then be delegated to a given participant. For simplicity and convenience, the participant creates new parties in their own namespace by default.

The weak coupling of parties to participants allows you to migrate parties together with their active contract set from one participant node to another. Note, the process below works only for parties that are hosted on a single node. Also, if the party is not fully controlled by the source participant node, you need to prepare the topology state change appropriately, disabling the party on the source node and delegating the party to the target node.

Starting with a party Alice being allocated on participant1:

@ val alice = participant1.parties.enable("Alice")
alice : PartyId = Alice::122094e03f90...

To migrate Alice to participant2, we follow a four-step process. First, we need to obtain the target participant id. In this example, we read it from the participant id:

@ val targetParticipantId = participant2.id
targetParticipantId : ParticipantId = PAR::participant2::1220d93bace9...

Next, we deactivate the party on the origin participant and store the party’s active contract set in a file by using the repair macros which are part of the enterprise edition:

@ repair.party_migration.step1_hold_and_store_acs(alice, participant1, targetParticipantId, "alice.acs.gz")
res3: Map[DomainId, Long] = Map()

The last argument is the name of a file which the active contract set is stored as base64 encoded strings, ordered by domain-id and contract-id. This file then needs to be transferred offline to the target participant. Additionally, the repair macro will disable the party on the first participant. This is important in order to avoid breaking the consistency of the exported active contract set.

The target participant must then be disconnected from the domain before it can import data:

@ participant2.domains.disconnect("mydomain")

Once the domain is disconnected, invoke the import command:

@ repair.party_migration.step2_import_acs(participant2, "alice.acs.gz")

When importing is finished, reconnect to the domain using:

@ participant2.domains.reconnect("mydomain")
res6: Boolean = true

The last step on the target participant enables the party:

@ repair.party_migration.step3_enable_on_target(alice, participant2)

Finally, purge the active contract set on the origin participant:

@ participant1.domains.disconnect("mydomain")

@ repair.party_migration.step4_clean_up_source(alice, participant1, "alice.acs.gz")

The above commands require interactive access to the participants and are supported as an alpha implementation. They work for parties that were allocated using standard methods on a single participant node. Otherwise, a few more manual steps are required to properly prepare the topology state before exporting and importing the topology state.

Party on Two Nodes

Note: this is an alpha feature only and is not supported in production.

Assuming we have party ("Alice", N1) which we want to host on two participants: ("participant1", N1) and ("participant2", N2). In this case, we have the party “Alice” in namespace N1, whereas the participant2 is in namespace N2. In order to set this up, we need to appropriately authorize the participants to act on behalf of the party and we need to correctly copy the active contract set.

Starting with a party being allocated on participant1:

@ val alice = participant1.parties.enable("Alice")
alice : PartyId = Alice::1220b0df7ff2...

To add this party to participant2, participant2 must first agree to host the party. This is done by authorizing the RequestSide.To of the party to participant mapping on the target participant:

@ participant2.topology.party_to_participant_mappings.authorize(TopologyChangeOp.Add, alice, participant2.id, RequestSide.To, ParticipantPermission.Submission)
res2: com.google.protobuf.ByteString = <ByteString@5a9db504 size=556 contents="\n\251\004\n\327\001\n\322\001\n\317\001\022 2CHw0geZODZs0Oy15dsEdwPGiJpdvOOM2...">

You can restrict the permission of the node by setting the appropriate ParticipantPermission in the authorization call to either Observation or Confirmation instead of the default Submission. This allows setups where a party is hosted with Submission permissions on one node and Confirmation on another to increase the liveness of the system.

Note

The distinction between Submission and Confirmation is only enforced in the participant node. A malicious participant node with Confirmation permission for a certain party can submit transactions in the name of the party. This is due to Canton’s high level of privacy where validators do not know the identity of the submitting participant. Therefore, a party who delegates Confirmation permissions to a participant should trust the participant sufficiently.

Before we continue, we need to ensure that the target participant is now disconnected from the affected domains, in order to avoid the target participant receiving transactions for the new party prior to the complete transfer of the active contract store. Therefore, we disconnect the participant from all domains:

@ participant2.domains.disconnect_all()

This is currently the reason why this feature is only supported as alpha: we can not guarantee that a user does not damage their system by accident due to forgetting to disconnect from the domain.

Next, add the RequestSide.From transaction such that the party is activated on the target participant:

@ participant1.topology.party_to_participant_mappings.authorize(TopologyChangeOp.Add, alice, participant2.id, RequestSide.From, ParticipantPermission.Submission)
res4: com.google.protobuf.ByteString = <ByteString@7c44ddad size=556 contents="\n\251\004\n\327\001\n\322\001\n\317\001\022 izOOo3KxgK0ckL0ut4bfaNhHmQnpSrI82...">

Check that the party is now hosted by two participants:

@ participant1.parties.list("Alice")
res5: Seq[ListPartiesResult] = Vector(
  ListPartiesResult(
    party = Alice::1220b0df7ff2...,
    participants = Vector(
      ParticipantDomains(
        participant = PAR::participant2::1220976a10c8...,
        domains = Vector(
          DomainPermission(domain = mydomain::12205fd2ded0..., permission = Submission)
        )
      ),
      ParticipantDomains(
        participant = PAR::participant1::1220b0df7ff2...,
        domains = Vector(
          DomainPermission(domain = mydomain::12205fd2ded0..., permission = Submission)
        )
      )
    )
  )
)

In the next step, you store the active contract set of the party into a file. If there is no traffic on the participant node and you can be sure that nothing has changed for the party, you can just straight use the repair.download command. Otherwise, you must find the timestamp when the party was activated. One way to find that timestamp is by looking at the topology store of that particular domain connection:

@ val timestamp = participant1.topology.party_to_participant_mappings.list(filterStore="mydomain", filterParty="Alice").map(_.context.validFrom).max
timestamp : Instant = 2023-03-09T09:51:20.133428Z

Take the max of the two timestamps which corresponds to the RequestSide.From topology transaction that you added above. Use this timestamp now to export the state using:

@ participant1.repair.download(Set(alice), "alice.acs.gz", filterDomainId="mydomain", timestamp = Some(timestamp))
res7: Map[DomainId, Long] = Map(mydomain::12205fd2ded0... -> 1L)

Note that you need to do this for every domain separately with the correct timestamp of the activation of the party. In our example, there is only one domain.

Subsequently, the active contract set is imported on the target participant:

@ repair.party_migration.step2_import_acs(participant2, "alice.acs.gz")

Once the entire active contract store has been imported, the target participant can reconnect to the domain:

@ participant2.domains.reconnect_all()

Now, both participant host the party and can act on behalf of it.

Manually Initializing a Node

There are situations where a node should not be automatically initialized, but where we prefer to control each step of the initialization. For example, when a node in the setup does not control its own identity, or when we do not want to store the identity key on the node for security reasons.

In the following, we demonstrate the basic steps how to initialise a node:

Domain Initialization

The following steps describe how to manually initialize a domain node:

// first, let's create a signing key that is going to control our identity
val identityKey = mydomain.keys.secret.generate_signing_key(name = "default")

// use the fingerprint of this key for our identity
val namespace = identityKey.fingerprint

// initialise the identity of this domain
val uid = mydomain.topology.init_id(identifier = "mydomain", fingerprint = namespace)

// create the root certificate for this namespace
mydomain.topology.namespace_delegations.authorize(
  ops = TopologyChangeOp.Add,
  namespace = namespace,
  authorizedKey = namespace,
  isRootDelegation = true,
)

// set the initial dynamic domain parameters for the domain
mydomain.topology.domain_parameters_changes
  .authorize(
    domainId = DomainId(uid),
    newParameters =
      ConsoleDynamicDomainParameters.defaultValues(protocolVersion = testedProtocolVersion),
    protocolVersion = testedProtocolVersion,
  )

val mediatorId = MediatorId(uid)
Seq[KeyOwner](DomainTopologyManagerId(uid), SequencerId(uid), mediatorId).foreach {
  keyOwner =>
    // in this case, we are using an embedded domain. therefore, we initialise all domain
    // entities at once. in a distributed setup, the process needs to be invoked on
    // the separate entities, and therefore requires a bit more coordination.
    // however, the steps remain the same.

    // first, create a signing key for this entity
    val signingKey = mydomain.keys.secret.generate_signing_key(
      name = keyOwner.code.threeLetterId.unwrap + "-signing-key"
    )

    // then, create a topology transaction linking the entity to the signing key
    mydomain.topology.owner_to_key_mappings.authorize(
      ops = TopologyChangeOp.Add,
      keyOwner = keyOwner,
      key = signingKey.fingerprint,
      purpose = KeyPurpose.Signing,
    )
}

// Register the mediator
mydomain.topology.mediator_domain_states.authorize(
  ops = TopologyChangeOp.Add,
  domain = mydomain.id,
  mediator = mediatorId,
  side = RequestSide.Both,
)

Participant Initialization

The following steps describe how to manually initialize a participant node:

// first, let's create a signing key that is going to control our identity
val identityKey =
  participant1.keys.secret.generate_signing_key(name = "my-identity")
// use the fingerprint of this key for our identity
val namespace = identityKey.fingerprint

// create the root certificate (self-signed)
participant1.topology.namespace_delegations.authorize(
  ops = TopologyChangeOp.Add,
  namespace = namespace,
  authorizedKey = namespace,
  isRootDelegation = true,
)

// initialise the id: this needs to happen AFTER we created the namespace delegation
// (on participants; for the domain, it's the other way around ... sorry for that)
// if we initialize the identity before we added the root certificate, then the system will
// complain about not being able to vet the admin workflow packages automatically.
// that would not be tragic, but would require a manual vetting step.
// in production, use a "random" identifier. for testing and development, use something
// helpful so you don't have to grep for hashes in your log files.
participant1.topology.init_id(identifier = "manualInit", fingerprint = namespace)

// create signing and encryption keys
val enc = participant1.keys.secret.generate_encryption_key()
val sig = participant1.keys.secret.generate_signing_key()

// assign new keys to this participant
Seq(enc, sig).foreach { key =>
  participant1.topology.owner_to_key_mappings.authorize(
    ops = TopologyChangeOp.Add,
    keyOwner = participant1.id,
    key = key.fingerprint,
    purpose = key.purpose,
  )
}