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Create a CType

Every KILT credential has to conform to a CType. A CType describes which properties a credential has and what type these properties have. CTypes must be registered on the Spiritnet blockchain. To learn more about CTypes, see the CType concept section.

The creation of a CType in KILT involves two steps: the definition of a CType and the anchoring of its hash on the KILT blockchain.

DID required

The creator of a CType is required to have a full DID with an attestation key. To see how to manage DIDs, please refer to the DID section.

CTypes are unique

The creation of a new CType requires the CType hash to be unique. Before writing a new CType, Attesters should check whether there is already an existing CType which matches their requirements.

Visit our CType index repository for a non-exhaustive list of existing CTypes.

The following snippets show how to create a CType:

import * as Kilt from '@kiltprotocol/sdk-js'

export async function createDriversLicenseCType(
  creator: Kilt.DidUri,
  submitterAccount: Kilt.KiltKeyringPair,
  signCallback: Kilt.SignExtrinsicCallback
): Promise<Kilt.ICType> {
  const api = Kilt.ConfigService.get('api')

  // Create a new CType definition.
  const ctype = Kilt.CType.fromProperties(`Drivers License by ${creator}`, {
    name: {
      type: 'string'
    },
    age: {
      type: 'integer'
    },
    id: {
      type: 'string'
    }
  })

  // Generate a creation tx.
  const encodedCtype = Kilt.CType.toChain(ctype)
  const ctypeCreationTx = api.tx.ctype.add(encodedCtype)
  // Sign it with the right DID key.
  const authorizedCtypeCreationTx = await Kilt.Did.authorizeTx(
    creator,
    ctypeCreationTx,
    signCallback,
    submitterAccount.address
  )
  // Submit the creation tx to the KILT blockchain
  // using the KILT account specified in the creation operation.
  await Kilt.Blockchain.signAndSubmitTx(
    authorizedCtypeCreationTx,
    submitterAccount
  )

  return ctype
}

Retrieve a CType from its ID​

CTypes can be queried directly from any KILT archive nodes. The following example shows how to query a CType using the SDK:

import * as Kilt from '@kiltprotocol/sdk-js'

export async function fetchCType(
  ctypeId: Kilt.ICType['$id']
): Promise<Kilt.CType.ICTypeDetails> {
  // Example CType ID: kilt:ctype:0x329a2a5861ea63c250763e5e4c4d4a18fe4470a31e541365c7fb831e5432b940
  return Kilt.CType.fetchFromChain(ctypeId)
}