KeyFactory

public class KeyFactory extends Object

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.

Protected Constructor Summary

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

Public Method Summary

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