SecretKeyFactory

public class SecretKeyFactory extends Object

This class represents a factory for secret keys.

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. Secret key factories operate only on secret (symmetric) keys.

Key factories are bi-directional, i.e., they allow 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.

Application developers should refer to their provider's documentation to find out which key specifications are supported by the generateSecret and getKeySpec methods. For example, the DES secret-key factory supplied by the "SunJCE" provider supports DESKeySpec as a transparent representation of DES keys, and that provider's secret-key factory for Triple DES keys supports DESedeKeySpec as a transparent representation of Triple DES keys.

Android provides the following SecretKeyFactory algorithms:

Algorithm	Supported API Levels
AES	23+
DES	1+
DESede	1+
HmacSHA1	23+
HmacSHA224	23+
HmacSHA256	23+
HmacSHA384	23+
HmacSHA512	23+
PBEwithHmacSHA1	1+
PBEwithHmacSHA1AndAES_128	26+
PBEwithHmacSHA1AndAES_256	26+
PBEwithHmacSHA224AndAES_128	26+
PBEwithHmacSHA224AndAES_256	26+
PBEwithHmacSHA256AndAES_128	26+
PBEwithHmacSHA256AndAES_256	26+
PBEwithHmacSHA384AndAES_128	26+
PBEwithHmacSHA384AndAES_256	26+
PBEwithHmacSHA512AndAES_128	26+
PBEwithHmacSHA512AndAES_256	26+
PBEwithMD5AND128BITAES-CBC-OPENSSL	1+
PBEwithMD5AND192BITAES-CBC-OPENSSL	1+
PBEwithMD5AND256BITAES-CBC-OPENSSL	1+
PBEwithMD5ANDDES	1+
PBEwithMD5ANDRC2	1+
PBEwithSHA1ANDDES	1+
PBEwithSHA1ANDRC2	1+
PBEwithSHA256AND128BITAES-CBC-BC	1+
PBEwithSHA256AND192BITAES-CBC-BC	1+
PBEwithSHA256AND256BITAES-CBC-BC	1+
PBEwithSHAAND128BITAES-CBC-BC	1+
PBEwithSHAAND128BITRC2-CBC	10+
PBEwithSHAAND128BITRC4	10+
PBEwithSHAAND192BITAES-CBC-BC	1+
PBEwithSHAAND2-KEYTRIPLEDES-CBC	1+
PBEwithSHAAND256BITAES-CBC-BC	1+
PBEwithSHAAND3-KEYTRIPLEDES-CBC	1+
PBEwithSHAAND40BITRC2-CBC	1+
PBEwithSHAAND40BITRC4	10+
PBEwithSHAANDTWOFISH-CBC	10+
PBKDF2withHmacSHA1	10+
PBKDF2withHmacSHA1And8BIT	19+
PBKDF2withHmacSHA224	26+
PBKDF2withHmacSHA256	26+
PBKDF2withHmacSHA384	26+
PBKDF2withHmacSHA512	26+

These algorithms are described in the SecretKeyFactory section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

See Also

• SecretKey
• DESKeySpec
• DESedeKeySpec
• PBEKeySpec

Protected Constructor Summary

SecretKeyFactory(SecretKeyFactorySpi keyFacSpi, Provider provider, String algorithm) Creates a SecretKeyFactory object.

Public Method Summary

final SecretKey	generateSecret(KeySpec keySpec) Generates a SecretKey object from the provided key specification (key material).
final String	getAlgorithm() Returns the algorithm name of this SecretKeyFactory object.
final static SecretKeyFactory	getInstance(String algorithm) Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
final static SecretKeyFactory	getInstance(String algorithm, String provider) Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
final static SecretKeyFactory	getInstance(String algorithm, Provider provider) Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.
final KeySpec	getKeySpec(SecretKey key, Class<?> keySpec) Returns a specification (key material) of the given key object in the requested format.
final Provider	getProvider() Returns the provider of this SecretKeyFactory object.
final SecretKey	translateKey(SecretKey key) Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this secret-key factory.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Protected Constructors

protected SecretKeyFactory (SecretKeyFactorySpi keyFacSpi, Provider provider, String algorithm)

Creates a SecretKeyFactory object.

Parameters

keyFacSpi	the delegate
provider	the provider
algorithm	the secret-key algorithm

Public Methods

public final SecretKey generateSecret (KeySpec keySpec)

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

Parameters

keySpec	the specification (key material) of the secret key

Returns

• the secret key

Throws

InvalidKeySpecException	if the given key specification is inappropriate for this secret-key factory to produce a secret key.

public final String getAlgorithm ()

Returns the algorithm name of this SecretKeyFactory object.

This is the same name that was specified in one of the getInstance calls that created this SecretKeyFactory object.

Returns

• the algorithm name of this SecretKeyFactory object.

public static final SecretKeyFactory getInstance (String algorithm)

Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new SecretKeyFactory object encapsulating the SecretKeyFactorySpi 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	the standard name of the requested secret-key algorithm. See the SecretKeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

Returns

• the new SecretKeyFactory object.

Throws

NullPointerException	if the specified algorithm is null.
NoSuchAlgorithmException	if no Provider supports a SecretKeyFactorySpi implementation for the specified algorithm.

See Also

• Provider

public static final SecretKeyFactory getInstance (String algorithm, String provider)

Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.

A new SecretKeyFactory object encapsulating the SecretKeyFactorySpi 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	the standard name of the requested secret-key algorithm. See the SecretKeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider	the name of the provider.

Returns

• the new SecretKeyFactory object.

Throws

NoSuchAlgorithmException	if a SecretKeyFactorySpi implementation for the specified algorithm is not available from the specified provider.
NullPointerException	if the specified algorithm is null.
NoSuchProviderException	if the specified provider is not registered in the security provider list.
IllegalArgumentException	if the provider is null or empty.

See Also

• Provider

public static final SecretKeyFactory getInstance (String algorithm, Provider provider)

Returns a SecretKeyFactory object that converts secret keys of the specified algorithm.

A new SecretKeyFactory object encapsulating the SecretKeyFactorySpi 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	the standard name of the requested secret-key algorithm. See the SecretKeyFactory section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider	the provider.

Returns

• the new SecretKeyFactory object.

Throws

NullPointerException	if the specified algorithm is null.
NoSuchAlgorithmException	if a SecretKeyFactorySpi implementation for the specified algorithm is not available from the specified Provider object.
IllegalArgumentException	if the provider is null.

See Also

• Provider

public final KeySpec getKeySpec (SecretKey key, Class<?> keySpec)

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

Parameters

key	the key
keySpec	the requested format in which the key material shall be returned

Returns

• the underlying key specification (key material) in the requested format

Throws

InvalidKeySpecException	if the requested key specification is inappropriate for the given key (e.g., the algorithms associated with key and keySpec do not match, or key references a key on a cryptographic hardware device whereas keySpec is the specification of a software-based key), or the given key cannot be dealt with (e.g., the given key has an algorithm or format not supported by this secret-key factory).

public final Provider getProvider ()

Returns the provider of this SecretKeyFactory object.

Returns

• the provider of this SecretKeyFactory object

public final SecretKey translateKey (SecretKey key)

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

Parameters

key	the key whose provider is unknown or untrusted

Returns

• the translated key

Throws

InvalidKeyException	if the given key cannot be processed by this secret-key factory.