anchors allows anchoring messages to the Tangle. Powered by IOTA Streams.
How it works
The main purpose is to be able to anchor messages to the IOTA Tangle so that their sequentiality, integrity, authenticity and immutability is preserved. Different applications can benefit from this feature. One of the applications (implemented by the ld-proofs library) is the generation of Linked Data Proofs for JSON(-LD) documents.
You can imagine an Anchoring Channel as a (public) port's dock where different ships can be anchored and where an anchorage is always available. The library allows anchoring a new arriving ship, and once it is anchored, such ship itself turns into the next anchorage. Actually, when you anchor a new ship, you anchor it both to the dock and to another ship, which is also playing the anchorage role.
An Anchoring Channel is just an IOTA Streams (Single Branch) Channel configured in Single Publisher mode. The publisher is usually both the Author and the only Subscriber of the Channel. The channel can contain as many anchorages as needed but each anchorage can only anchor one message. The first anchorage is the announce message of such an IOTA Streams Channel. Anchorages are identified by an ID (the ID of a message).
After anchoring a message, such anchored message turns itself into the next anchorage available.
The entities anchoring the messages (the ship owners, metaphorically speaking) are authenticated by means of EdDSA (Ed25519).
npm install @tangle-js/anchors
// Seed generated automatically. Channel on the mainnet. Author === Subscriber. const anchoringChannel = await IotaAnchoringChannel.bindNew(); // Creation of a new channel by the Author // Channel details contains all the relevant info about the channel just created const channelDetails = await IotaAnchoringChannel.create(SeedHelper.generateSeed()); // Properties available on a Channel object anchoringChannel.seed // The seed of the Subscriber currently bound to the channel anchoringChannel.channelID anchoringChannel.channelAddr anchoringChannel.firstAnchorageID anchoringChannel.subscriberPubKey // The Subscriber's Public Key (can be the same as Author's) anchoringChannel.authorPubKey // The Author's Public Key
Channel instantiation from ID
// Instantiation and binding as Subscriber using the seed const anchoringChannel = await IotaAnchoringChannel.fromID(channelID).bind(seed);
const message = "my message"; // Obtain your anchorageID (it could be the first anchorageID of the channel) const result = await anchoringChannel.anchor(Buffer.from(message), anchorageID); console.log("msg ID", result.msgID);
Searches for the anchorageID and fetches the message anchored to it.
Optionally an expected message ID can be passed that allows to fail if there is no matching between the fetched message ID and the expected message ID.
const result = await anchoringChannel.fetch(anchorageID, expectedMsgID?); console.log("Message content: ", result.message.toString()); console.log("Message ID: ", result.msgID); console.log("Message publisher's PK: ", result.pk);
Receives a message that has already been seen on the channel.
Optionally an expected anchorage ID can be passed that allows to fail if the target message is not actually anchored to the expected anchorage.
const result = await anchoringChannel.receive(msgID, expectedAnchorageID?);
const next = await anchoringChannel.fetchNext();