net.i2p.crypto.elgamal

Class KeyFactory

java.lang.Object

java.security.KeyFactorySpi

net.i2p.crypto.elgamal.KeyFactory

public final class KeyFactory
extends KeyFactorySpi

Java Security Provider KeyFactory implementation for ElGamal public-key cryptosystem. This class provides the bridge between ElGamal-specific key specifications and the standard Java Cryptography Architecture (JCA) KeyFactory interface. It enables conversion between different key representations and supports standard encoding formats for ElGamal operations within the I2P network.

Supported Operations:

• Key Generation: Create ElGamal keys from specifications
• Key Conversion: Translate between different key formats
• Standard Encoding: Support for PKCS#8 and X.509 formats
• Key Specification: Extract key parameters from existing keys

Supported Key Specifications:

• ElGamalPublicKeySpec - ElGamal-specific public key specification
• ElGamalPrivateKeySpec - ElGamal-specific private key specification
• PKCS8EncodedKeySpec - Standard PKCS#8 private key encoding
• X509EncodedKeySpec - Standard X.509 public key encoding

Usage Example:

 // Create KeyFactory instance
 KeyFactory keyFactory = KeyFactory.getInstance("ElGamal", "I2P");

 // Generate private key from specification
 ElGamalParameterSpec params = new ElGamalParameterSpec(p, g);
 ElGamalPrivateKeySpec privSpec = new ElGamalPrivateKeySpec(privateKey, params);
 ElGamalPrivateKey privateKey = (ElGamalPrivateKey) keyFactory.generatePrivate(privSpec);

 // Convert to standard PKCS#8 format
 PKCS8EncodedKeySpec pkcs8Spec = keyFactory.getKeySpec(privateKey, PKCS8EncodedKeySpec.class);
 

Thread Safety: This class is thread-safe and can be used concurrently by multiple threads. Key objects created by this factory are immutable and thread-safe.

Security Considerations:

• Private key material is handled securely during conversion
• Standard encoding formats ensure interoperability with other providers
• ElGamal parameters are validated during key creation

See Also:

KeyFactory, ElGamalPublicKey, ElGamalPrivateKey, I2PProvider

Constructor Summary

Constructors

Constructor and Description
KeyFactory()

Method Summary

Modifier and Type	Method and Description
protected PrivateKey	engineGeneratePrivate(KeySpec keySpec) Generates an ElGamal private key from the provided key specification.
protected PublicKey	engineGeneratePublic(KeySpec keySpec) Generates an ElGamal public key from the provided key specification.
protected <T extends KeySpec> T	engineGetKeySpec(Key key, Class<T> keySpec) Returns a specification (key material) of the given key object.
protected Key	engineTranslateKey(Key key) Translates a key object from one provider to another.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

KeyFactory

public KeyFactory()

Method Detail

engineGeneratePrivate

protected PrivateKey engineGeneratePrivate(KeySpec keySpec)
                                    throws InvalidKeySpecException

Generates an ElGamal private key from the provided key specification. This method converts various key specification formats into ElGamal private keys, supporting both ElGamal-specific specifications and standard PKCS#8 encoding.

Specified by:

engineGeneratePrivate in class KeyFactorySpi

Parameters:

keySpec - the key specification to convert

Returns:

the generated ElGamal private key

Throws:

InvalidKeySpecException - if the key specification is unsupported or malformed

engineGeneratePublic

protected PublicKey engineGeneratePublic(KeySpec keySpec)
                                  throws InvalidKeySpecException

Generates an ElGamal public key from the provided key specification. This method converts various key specification formats into ElGamal public keys, supporting both ElGamal-specific specifications and standard X.509 encoding.

Specified by:

engineGeneratePublic in class KeyFactorySpi

Parameters:

keySpec - the key specification to convert

Returns:

the generated ElGamal public key

Throws:

InvalidKeySpecException - if the key specification is unsupported or malformed

engineGetKeySpec

protected <T extends KeySpec> T engineGetKeySpec(Key key,
                                                 Class<T> keySpec)
                                          throws InvalidKeySpecException

Returns a specification (key material) of the given key object. This method extracts the underlying key parameters from ElGamal keys and converts them into the requested specification format.

Specified by:

engineGetKeySpec in class KeyFactorySpi

Type Parameters:

T - the type of the returned key specification

Parameters:

key - the key to convert

keySpec - the requested specification class

Returns:

the corresponding key specification

Throws:

InvalidKeySpecException - if the requested specification type is unsupported or the key cannot be converted

engineTranslateKey

protected Key engineTranslateKey(Key key)
                          throws InvalidKeyException

Translates a key object from one provider to another. This method would allow conversion between ElGamal keys from different security providers, but currently no other ElGamal providers are known or supported in the I2P environment.

Specified by:

engineTranslateKey in class KeyFactorySpi

Parameters:

key - the key to translate

Returns:

the translated key

Throws:

InvalidKeyException - always, as no other ElGamal providers are supported