WritableIdentityCredential

public abstract @NonNull Collection<X509Certificate> getCredentialKeyCertificateChain(@NonNull byte[] challenge)

Generates and returns an X.509 certificate chain for the CredentialKey which identifies this credential to the issuing authority. The certificate contains an Android Keystore attestation extension which describes the key and the security hardware in which it lives.

The issuer MUST carefully examine this certificate chain including (but not limited to) checking that the root certificate is well-known, whether the tag Tag::IDENTITY_CREDENTIAL_KEY is present, the passed in challenge is present, the tag Tag::ATTESTATION_APPLICATION_ID is set to the expected Android application, the device has verified boot enabled, each certificate in the chain is signed by its successor, none of the certificates have been revoked, and so on.

If WritableIdentityCredential is not hardware-backed the credential is implemented using Android Keystore and the attestation extension will not contain the tag Tag::IDENTITY_CREDENTIAL_KEY. Otherwise if this tag is present it signals that WritableIdentityCredential is hardware-backed and CredentialKey and corresponding authentication keys can only sign/MAC very specific messages. This is in contrast to Android Keystore key which can be used to sign/MAC anything.

It is not strictly necessary to use this method to provision a credential if the issuing authority doesn't care about the nature of the security hardware. If called, however, this method must be called before personalize.

public abstract @NonNull byte[] personalize(@NonNull PersonalizationData personalizationData)

Stores all of the data in the credential, with the specified access control profiles.

This method returns a COSE_Sign1 data structure signed by the CredentialKey with payload set to ProofOfProvisioning as defined below.

    ProofOfProvisioning = [
         "ProofOfProvisioning",        ; tstr
         tstr,                         ; DocType
         [ * AccessControlProfile ],
         ProvisionedData,
         bool                          ; true if this is a test credential, should
                                       ; always be false.
     ]

     AccessControlProfile = {
         "id": uint,
         ? "readerCertificate" : bstr,
         ? (
              "userAuthenticationRequired" : bool,
              "timeoutMillis" : uint,
         )
     }

     ProvisionedData = {
         * Namespace => [ + Entry ]
     },

     Namespace = tstr

     Entry = {
         "name" : tstr,
         "value" : any,
         "accessControlProfiles" : [ * uint ],
     }

This data structure provides a guarantee to the issuer about the data which may be returned in the CBOR returned by getAuthenticatedData during a credential presentation.