java.lang.Object javax.crypto.KeyGenerator
This class provides the functionality of a (symmetric) key generator.
Key generators are constructed using one of the getInstance class methods of this class.
KeyGenerator objects are reusable, i.e., after a key has been generated, the same KeyGenerator object can be re-used to generate further keys.
There are two ways to generate a key: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:
All key generators share the concepts of a keysize and a source of randomness . There is an init method in this KeyGenerator class that takes these two universally shared types of arguments. There is also one that takes just a keysize argument, and uses the SecureRandom implementation of the highest-priority installed provider as the source of randomness (or a system-provided source of randomness if none of the installed providers supply a SecureRandom implementation), and one that takes just a source of randomness.
Since no other parameters are specified when you call the above algorithm-independent init methods, it is up to the provider what to do about the algorithm-specific parameters (if any) to be associated with each of the keys.
For situations where a set of algorithm-specific parameters already exists, there are two init methods that have an AlgorithmParameterSpec argument. One also has a SecureRandom argument, while the other uses the SecureRandom implementation of the highest-priority installed provider as the source of randomness (or a system-provided source of randomness if none of the installed providers supply a SecureRandom implementation).
In case the client does not explicitly initialize the KeyGenerator (via a call to an init method), each provider must supply (and document) a default initialization.
Constructor Summary | |
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protected |
KeyGenerator
(
KeyGeneratorSpi
keyGenSpi,
Provider
provider,
String
algorithm) Creates a KeyGenerator object. |
Method Summary | |
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SecretKey |
generateKey
() Generates a secret key. |
String |
getAlgorithm
() Returns the algorithm name of this KeyGenerator object. |
static KeyGenerator |
getInstance
(
String
algorithm) Generates a KeyGenerator object for the specified algorithm. |
static KeyGenerator |
getInstance
(
String
algorithm,
Provider
provider) Generates a KeyGenerator object for the specified key algorithm from the specified provider. |
static KeyGenerator |
getInstance
(
String
algorithm,
String
provider) Generates a KeyGenerator object for the specified key algorithm from the specified provider. |
Provider |
getProvider
() Returns the provider of this KeyGenerator object. |
void |
init
(
AlgorithmParameterSpec
params) Initializes this key generator with the specified parameter set. |
void |
init
(
AlgorithmParameterSpec
params,
SecureRandom
random) Initializes this key generator with the specified parameter set and a user-provided source of randomness. |
void |
init
(int keysize) Initializes this key generator for a certain keysize. |
void |
init
(int keysize,
SecureRandom
random) Initializes this key generator for a certain keysize, using a user-provided source of randomness. |
void |
init
(
SecureRandom
random) Initializes this key generator. |
Methods inherited from class java.lang. Object |
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clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
Constructor Detail |
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protected KeyGenerator(KeyGeneratorSpi keyGenSpi, Provider provider, String algorithm)
Method Detail |
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public final String getAlgorithm()
This is the same name that was specified in one of the getInstance calls that created this KeyGenerator object.
public static final KeyGenerator getInstance(String algorithm) throws NoSuchAlgorithmException
public static final KeyGenerator getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
public static final KeyGenerator getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
public final Provider getProvider()
public final void init(SecureRandom random)
public final void init(AlgorithmParameterSpec params) throws InvalidAlgorithmParameterException
If this key generator requires any random bytes, it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)
public final void init(AlgorithmParameterSpec params, SecureRandom random) throws InvalidAlgorithmParameterException
public final void init(int keysize)
If this key generator requires any random bytes, it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)
public final void init(int keysize, SecureRandom random)
public final SecretKey generateKey()