oid4vcwallet/dev.idfoundry.oid4vcwallet/AndroidKeystoreKeyStore

AndroidKeystoreKeyStore

class AndroidKeystoreKeyStore(val options: AndroidKeystoreKeyStore.Options = Options(), authenticator: HolderAuthenticator? = null) : KeyStore, KeyAgreement(source)

The wallet's keys, in Android Keystore: P-256 keys whose private halves never leave its secure hardware — StrongBox where the device has it (Options.strongBox), else the TEE. Each key's ID is its Keystore alias after Options.aliasPrefix. Keys are usable only while the device is unlocked, and holder keys, if Options.holderUserAuthentication, each time they sign only after authenticator has authenticated the holder: the store refuses to be made without one then.

Constructors

constructor(options: AndroidKeystoreKeyStore.Options = Options(), authenticator: HolderAuthenticator? = null)

Types

Options

data class Options(val strongBox: AndroidKeystoreKeyStore.StrongBox = StrongBox.PREFERRED, val holderUserAuthentication: Boolean = true, val aliasPrefix: String = "org.idfoundry.oid4vcgo.key.", val holderKeyAgreement: Boolean = false)

How an AndroidKeystoreKeyStore makes keys: by default in StrongBox where the device has it, holder keys asking for the holder each time.

StrongBox

enum StrongBox : Enum<AndroidKeystoreKeyStore.StrongBox>

Where keys are made.

Properties

isDurable

open override val isDurable: Boolean

Keystore keys survive the app quitting.

options

val options: AndroidKeystoreKeyStore.Options

How the store makes keys.

Functions

agree

open override fun agree(id: String, peerPublicKey: ByteArray): ByteArray

ECDH between holder key id and peerPublicKey inside Android Keystore. A key made without PURPOSE_AGREE_KEY (see Options.holderKeyAgreement), below API 31, or requiring the holder, throws KeyAgreementUnsupportedException: the wallet signs.

createKey

open override fun createKey(purpose: KeyPurpose): String

Creates a P-256 key for purpose and returns its ID.

deleteKey

open override fun deleteKey(id: String)

Deletes the key; deleting one that doesn't exist isn't an error.

deleteKeys

fun deleteKeys(except: Set<String>): Int

Deletes every key this store holds except except, and returns how many it deleted. Wallet.sweepOrphanedKeys calls it with the keys the wallet's credentials are bound to.

keyIDs

fun keyIDs(): List<String>

The IDs of every key this store holds (under its alias prefix).

publicKey

open override fun publicKey(id: String): ByteArray?

The key's public key as an uncompressed X9.63 point (0x04 || X || Y), or null when there's no such key.

securityLevel

fun securityLevel(id: String): Int?

Where key id lives, as a KeyProperties.SECURITY_LEVEL_ value: StrongBox, the TEE, or software. Android 11 can't tell StrongBox from the TEE: there, a key in secure hardware is the TEE's. (The constants are API 31's, but compile-time ints: they work on 30.)

sign

open override fun sign(id: String, digest: ByteArray): ByteArray

Signs a SHA-256 digest with the key, returning an ASN.1 DER ECDSA signature. A holder key may ask the holder to authenticate here.