Added in API level 1

Summary: Protected Ctors | Methods | Inherited Methods

KeyFactory

public class KeyFactory
extends Object

java.lang.Object
↳	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
XDH	33+

See also:

Summary

Protected constructors
`KeyFactory(KeyFactorySpi keyFacSpi, Provider provider, String algorithm)` Creates a KeyFactory object.

Public methods
`final PrivateKey`	`generatePrivate(KeySpec keySpec)` Generates a private key object from the provided key specification (key material).
`final PublicKey`	`generatePublic(KeySpec keySpec)` Generates a public key object from the provided key specification (key material).
`final String`	`getAlgorithm()` Gets the name of the algorithm associated with this `KeyFactory`.
`static KeyFactory`	`getInstance(String algorithm)` Returns a KeyFactory object that converts public/private keys of the specified algorithm.
`static KeyFactory`	`getInstance(String algorithm, String provider)` Returns a KeyFactory object that converts public/private keys of the specified algorithm.
`static KeyFactory`	`getInstance(String algorithm, Provider provider)` Returns a KeyFactory object that converts public/private keys of the specified algorithm.
`final <T extends KeySpec> T`	`getKeySpec(Key key, Class<T> keySpec)` Returns a specification (key material) of the given key object.
`final Provider`	`getProvider()` Returns the provider of this key factory object.
`final Key`	`translateKey(Key key)` Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Protected constructors

KeyFactory

Added in API level 1

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

Creates a KeyFactory object.

Parameters
`keyFacSpi`	`KeyFactorySpi`: the delegate
`provider`	`Provider`: the provider
`algorithm`	`String`: the name of the algorithm to associate with this `KeyFactory`

Public methods

generatePrivate

Added in API level 1

public final PrivateKey generatePrivate (KeySpec keySpec)

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

Parameters
`keySpec`	`KeySpec`: the specification (key material) of the private key.

Returns
`PrivateKey`	the private key.

Throws
`InvalidKeySpecException`	if the given key specification is inappropriate for this key factory to produce a private key.

generatePublic

Added in API level 1

public final PublicKey generatePublic (KeySpec keySpec)

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

Parameters
`keySpec`	`KeySpec`: the specification (key material) of the public key.

Returns
`PublicKey`	the public key.

Throws
`InvalidKeySpecException`	if the given key specification is inappropriate for this key factory to produce a public key.

getAlgorithm

Added in API level 1

public final String getAlgorithm ()

Gets the name of the algorithm associated with this KeyFactory.

Returns
`String`	the name of the algorithm associated with this `KeyFactory`

getInstance

Added in API level 1

public static KeyFactory getInstance (String algorithm)

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.

Returns
`KeyFactory`	the new `KeyFactory` object

Throws
`NoSuchAlgorithmException`	if no `Provider` supports a `KeyFactorySpi` implementation for the specified algorithm
`NullPointerException`	if `algorithm` is `null` on Android 14 or above

See also:

Provider

getInstance

Added in API level 1

public static KeyFactory getInstance (String algorithm, 
                String provider)

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.
`provider`	`String`: the name of the provider.

Returns
`KeyFactory`	the new `KeyFactory` object

Throws
`IllegalArgumentException`	if the provider name is `null` or empty
`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
`NullPointerException`	if `algorithm` is `null` on Android 14 or above

See also:

Provider

getInstance

Added in API level 1

public static KeyFactory getInstance (String algorithm, 
                Provider provider)

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.
`provider`	`Provider`: the provider.

Returns
`KeyFactory`	the new `KeyFactory` object

Throws
`IllegalArgumentException`	if the specified provider is `null`
`NoSuchAlgorithmException`	if a `KeyFactorySpi` implementation for the specified algorithm is not available from the specified `Provider` object
`NullPointerException`	if `algorithm` is `null` on Android 14 or above

See also:

Provider

getKeySpec

Added in API level 1

public final T getKeySpec (Key key, 
                Class<T> keySpec)

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
`key`	`Key`: the key.
`keySpec`	`Class`: the specification class in which the key material should be returned.

Returns
`T`	the underlying key specification (key material) in an instance of the requested specification class.

Throws
`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).

getProvider

Added in API level 1

public final Provider getProvider ()

Returns the provider of this key factory object.

Returns
`Provider`	the provider of this key factory object

translateKey

Added in API level 1

public final Key translateKey (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.

Returns
`Key`	the translated key.

Throws
`InvalidKeyException`	if the given key cannot be processed by this key factory.