KeyFactory

open class KeyFactory
kotlin.Any
   ↳ java.security.KeyFactory

Key factories are used to convert keys (opaque cryptographic keys of type Key) into key specifications (transparent representations of the underlying key material), and vice versa.

Key factories are bi-directional. That is, they allow you to build an opaque key object from a given key specification (key material), or to retrieve the underlying key material of a key object in a suitable format.

Multiple compatible key specifications may exist for the same key. For example, a DSA public key may be specified using DSAPublicKeySpec or X509EncodedKeySpec. A key factory can be used to translate between compatible key specifications.

The following is an example of how to use a key factory in order to instantiate a DSA public key from its encoding. Assume Alice has received a digital signature from Bob. Bob also sent her his public key (in encoded format) to verify his signature. Alice then performs the following actions:

 X509EncodedKeySpec bobPubKeySpec = new X509EncodedKeySpec(bobEncodedPubKey); KeyFactory keyFactory = KeyFactory.getInstance("DSA"); PublicKey bobPubKey = keyFactory.generatePublic(bobPubKeySpec); Signature sig = Signature.getInstance("DSA"); sig.initVerify(bobPubKey); sig.update(data); sig.verify(signature); 

Android provides the following KeyFactory algorithms:

Algorithm Supported API Levels DH 1+ DSA 1+ EC 11+ RSA 1+ X.509 1-8 These algorithms are described in the KeyFactory section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

Summary

Protected constructors
<init>(keyFacSpi: KeyFactorySpi!, provider: Provider!, algorithm: String!)

Creates a KeyFactory object.

Public methods
Key!

Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.

String!

Gets the name of the algorithm associated with this KeyFactory.

T
getKeySpec(key: Key!, keySpec: Class<T>!)

Returns a specification (key material) of the given key object.

PublicKey!

Generates a public key object from the provided key specification (key material).

Provider!

Returns the provider of this key factory object.

PrivateKey!

Generates a private key object from the provided key specification (key material).

open static KeyFactory!
getInstance(algorithm: String!)

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

open static KeyFactory!
getInstance(algorithm: String!, provider: String!)

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

open static KeyFactory!
getInstance(algorithm: String!, provider: Provider!)

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

Protected constructors

<init>

protected KeyFactory(keyFacSpi: KeyFactorySpi!, provider: Provider!, algorithm: String!)

Creates a KeyFactory object.

Parameters
keyFacSpi KeyFactorySpi!: the delegate
provider KeyFactorySpi!: the provider
algorithm KeyFactorySpi!: the name of the algorithm to associate with this KeyFactory

Public methods

translateKey

fun translateKey(key: Key!): Key!

Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.

Parameters
key Key!: the key whose provider is unknown or untrusted.
Return
Key!: the translated key.
Exceptions
InvalidKeyException if the given key cannot be processed by this key factory.

getAlgorithm

fun getAlgorithm(): String!

Gets the name of the algorithm associated with this KeyFactory.

Return
String!: the name of the algorithm associated with this KeyFactory

getKeySpec

fun <T : KeySpec!> getKeySpec(key: Key!, keySpec: Class<T>!): T

Returns a specification (key material) of the given key object. keySpec identifies the specification class in which the key material should be returned. It could, for example, be DSAPublicKeySpec.class, to indicate that the key material should be returned in an instance of the DSAPublicKeySpec class.

Parameters
<T> Key!: the type of the key specification to be returned
key Key!: the key.
keySpec Key!: the specification class in which the key material should be returned.
Return
T: the underlying key specification (key material) in an instance of the requested specification class.
Exceptions
InvalidKeySpecException if the requested key specification is inappropriate for the given key, or the given key cannot be processed (e.g., the given key has an unrecognized algorithm or format).

generatePublic

fun generatePublic(keySpec: KeySpec!): PublicKey!

Generates a public key object from the provided key specification (key material).

Parameters
keySpec KeySpec!: the specification (key material) of the public key.
Return
PublicKey!: the public key.
Exceptions
InvalidKeySpecException if the given key specification is inappropriate for this key factory to produce a public key.

getProvider

fun getProvider(): Provider!

Returns the provider of this key factory object.

Return
Provider!: the provider of this key factory object

generatePrivate

fun generatePrivate(keySpec: KeySpec!): PrivateKey!

Generates a private key object from the provided key specification (key material).

Parameters
keySpec KeySpec!: the specification (key material) of the private key.
Return
PrivateKey!: the private key.
Exceptions
InvalidKeySpecException if the given key specification is inappropriate for this key factory to produce a private key.

getInstance

open static fun getInstance(algorithm: String!): KeyFactory!

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new KeyFactory object encapsulating the KeyFactorySpi implementation from the first Provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

Parameters
algorithm String!: the name of the requested key algorithm. See the KeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
Return
KeyFactory!: the new KeyFactory object.
Exceptions
NoSuchAlgorithmException if no Provider supports a KeyFactorySpi implementation for the specified algorithm.

See Also

getInstance

open static fun getInstance(algorithm: String!, provider: String!): KeyFactory!

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

A new KeyFactory object encapsulating the KeyFactorySpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

Parameters
algorithm String!: the name of the requested key algorithm. See the KeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider String!: the name of the provider.
Return
KeyFactory!: the new KeyFactory object.
Exceptions
NoSuchAlgorithmException if a KeyFactorySpi implementation for the specified algorithm is not available from the specified provider.
NoSuchProviderException if the specified provider is not registered in the security provider list.
IllegalArgumentException if the provider name is null or empty.

See Also

getInstance

added in API level 1.4
open static fun getInstance(algorithm: String!, provider: Provider!): KeyFactory!

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

A new KeyFactory object encapsulating the KeyFactorySpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.

Parameters
algorithm String!: the name of the requested key algorithm. See the KeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider String!: the provider.
Return
KeyFactory!: the new KeyFactory object.
Exceptions
NoSuchAlgorithmException if a KeyFactorySpi implementation for the specified algorithm is not available from the specified Provider object.
IllegalArgumentException if the specified provider is null.

See Also