Skip to content

Most visited

Recently visited

navigation
Added in API level 1

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:

Name 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.

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

Protected constructors

KeyFactory

Added in API level 1
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
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
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
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
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. See the KeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
Returns
KeyFactory the new KeyFactory object.
Throws
NoSuchAlgorithmException if no Provider supports a KeyFactorySpi implementation for the specified algorithm.

See also:

getInstance

Added in API level 1
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. 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.
Returns
KeyFactory the new KeyFactory object.
Throws
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
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. See the KeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider Provider: the provider.
Returns
KeyFactory the new KeyFactory object.
Throws
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:

getKeySpec

Added in API level 1
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
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
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.
This site uses cookies to store your preferences for site-specific language and display options.

Hooray!

This class requires API level or higher

This doc is hidden because your selected API level for the documentation is . You can change the documentation API level with the selector above the left navigation.

For more information about specifying the API level your app requires, read Supporting Different Platform Versions.