# Class SecretKeyFactory

java.lang.Object
javax.crypto.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 bidirectional, 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 DESede (Triple DES) secret key factory supplied by the "SunJCE" provider supports `DESedeKeySpec` as a transparent representation of Triple DES keys.

Every implementation of the Java platform is required to support the following standard `SecretKeyFactory` algorithms:

- `DESede`

These algorithms are described in the SecretKeyFactory section of the Java Security Standard Algorithm Names Specification. Consult the release documentation for your implementation to see if any other algorithms are supported.

Since:
  1.4
External Specifications
  - Java Security Standard Algorithm Names
See Also:
  - `SecretKey`
  - `DESedeKeySpec`
  - `PBEKeySpec`

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`SecretKeyFactory(SecretKeyFactorySpi keyFacSpi, Provider provider, String algorithm)`
Creates a `SecretKeyFactory` object.

## Method Summary

Modifier and Type
Method
Description
`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.
`static final SecretKeyFactory`
`getInstance(String algorithm)`
Returns a `SecretKeyFactory` object that converts secret keys of the specified algorithm.
`static final SecretKeyFactory`
`getInstance(String algorithm, String provider)`
Returns a `SecretKeyFactory` object that converts secret keys of the specified algorithm.
`static final 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.

### Methods declared in class Object

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

## Constructor Details

### SecretKeyFactory

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

Parameters:
  `keyFacSpi` - the delegate
  `provider` - the provider
  `algorithm` - the secret key algorithm

## Method Details

### getInstance

public static final SecretKeyFactory getInstance(String algorithm) throws NoSuchAlgorithmException
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.

Implementation Note:
  The JDK Reference Implementation additionally uses the `jdk.security.provider.preferred` `Security` property to determine the preferred provider order for the specified algorithm. This may be different from the order of providers returned by `Security.getProviders()`.
Parameters:
  `algorithm` - the standard name of the requested secret key algorithm. See the SecretKeyFactory section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
Returns:
  the new `SecretKeyFactory` object
Throws:
  `NoSuchAlgorithmException` - if no `Provider` supports a `SecretKeyFactorySpi` implementation for the specified algorithm
  `NullPointerException` - if `algorithm` is `null`
External Specifications
  - Java Security Standard Algorithm Names
See Also:
  - `Provider`

### getInstance

public static final SecretKeyFactory getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
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 Security Standard Algorithm Names Specification for information about standard algorithm names.
  `provider` - the name of the provider.
Returns:
  the new `SecretKeyFactory` object
Throws:
  `IllegalArgumentException` - if the `provider` is `null` or empty
  `NoSuchAlgorithmException` - if a `SecretKeyFactorySpi` 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`
External Specifications
  - Java Security Standard Algorithm Names
See Also:
  - `Provider`

### getInstance

public static final SecretKeyFactory getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
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 Security Standard Algorithm Names Specification for information about standard algorithm names.
  `provider` - the provider.
Returns:
  the new `SecretKeyFactory` object
Throws:
  `IllegalArgumentException` - if the `provider` is `null`
  `NoSuchAlgorithmException` - if a `SecretKeyFactorySpi` implementation for the specified algorithm is not available from the specified `Provider` object
  `NullPointerException` - if `algorithm` is `null`
External Specifications
  - Java Security Standard Algorithm Names
See Also:
  - `Provider`

### getProvider

public final Provider getProvider()
Returns the provider of this `SecretKeyFactory` object.

Returns:
  the provider of this `SecretKeyFactory` object

### getAlgorithm

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.

### generateSecret

public final SecretKey generateSecret(KeySpec keySpec) throws InvalidKeySpecException
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.

### getKeySpec

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

### translateKey

public final SecretKey translateKey(SecretKey key) throws InvalidKeyException
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.