Package com.android.identity

Class WritableIdentityCredential

java.lang.Object

com.android.identity.WritableIdentityCredential

public abstract class WritableIdentityCredential
extends java.lang.Object

Class used to personalize a new identity credential.

Note that the credential is not persisted until calling personalize(PersonalizationData).

Once persisted, the PII in a credential can be updated using IdentityCredential.update(PersonalizationData). Use IdentityCredentialStore.createCredential(String, String) to create a new credential.

Method Summary

Modifier and Type	Method	Description
abstract java.util.Collection<java.security.cert.X509Certificate>	getCredentialKeyCertificateChain(byte[] challenge)	Generates and returns an X.509 certificate chain for the CredentialKey which identifies this credential to the issuing authority.
abstract byte[]	personalize(PersonalizationData personalizationData)	Stores all of the data in the credential, with the specified access control profiles.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getCredentialKeyCertificateChain

@NonNull
public abstract java.util.Collection<java.security.cert.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has verified boot enabled, each certificate in the chain is signed by its successor, none of the certificates have been revoked, and so on.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(PersonalizationData).

Note that the credential is not persisted until calling personalize(PersonalizationData).

Parameters:

challenge - is a non-empty byte array whose contents should be unique, fresh and provided by the issuing authority. The value provided is embedded in the attestation extension and enables the issuing authority to verify that the attestation certificate is fresh.

Returns:

the X.509 certificate for this credential's CredentialKey.

personalize

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

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

The credential is persisted only after this method returns successfully.

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 ResultData.getAuthenticatedData() during a credential presentation.

Parameters:

personalizationData - The data to provision, including access control profiles and data elements and their values, grouped into namespaces.

Returns:

A COSE_Sign1 data structure, see above.