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Added in API level 1

KeyGenerator

public class KeyGenerator
extends Object

java.lang.Object
   ↳ javax.crypto.KeyGenerator


This class provides the functionality of a secret (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:

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.

Android provides the following KeyGenerator algorithms:

Name Supported (API Levels)
AES 1+
AESWRAP 1–8
ARC4 14+
Blowfish 10+
DES 1+
DESede 1+
DESedeWRAP 1–8
HmacMD5 1+
HmacSHA1 1+
HmacSHA224 1–8,22+
HmacSHA256 1+
HmacSHA384 1+
HmacSHA512 1+
RC4 10–13
These algorithms are described in the KeyGenerator section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

See also:

Summary

Protected constructors

KeyGenerator(KeyGeneratorSpi keyGenSpi, Provider provider, String algorithm)

Creates a KeyGenerator object.

Public methods

final SecretKey generateKey()

Generates a secret key.

final String getAlgorithm()

Returns the algorithm name of this KeyGenerator object.

static final KeyGenerator getInstance(String algorithm)

Returns a KeyGenerator object that generates secret keys for the specified algorithm.

static final KeyGenerator getInstance(String algorithm, String provider)

Returns a KeyGenerator object that generates secret keys for the specified algorithm.

static final KeyGenerator getInstance(String algorithm, Provider provider)

Returns a KeyGenerator object that generates secret keys for the specified algorithm.

final Provider getProvider()

Returns the provider of this KeyGenerator object.

final void init(AlgorithmParameterSpec params, SecureRandom random)

Initializes this key generator with the specified parameter set and a user-provided source of randomness.

final void init(SecureRandom random)

Initializes this key generator.

final void init(int keysize)

Initializes this key generator for a certain keysize.

final void init(int keysize, SecureRandom random)

Initializes this key generator for a certain keysize, using a user-provided source of randomness.

final void init(AlgorithmParameterSpec params)

Initializes this key generator with the specified parameter set.

Inherited methods

From class java.lang.Object

Protected constructors

KeyGenerator

Added in API level 1
KeyGenerator (KeyGeneratorSpi keyGenSpi, 
                Provider provider, 
                String algorithm)

Creates a KeyGenerator object.

Parameters
keyGenSpi KeyGeneratorSpi: the delegate
provider Provider: the provider
algorithm String: the algorithm

Public methods

generateKey

Added in API level 1
SecretKey generateKey ()

Generates a secret key.

Returns
SecretKey the new key

getAlgorithm

Added in API level 1
String getAlgorithm ()

Returns the algorithm name of this KeyGenerator object.

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

Returns
String the algorithm name of this KeyGenerator object.

getInstance

Added in API level 1
KeyGenerator getInstance (String algorithm)

Returns a KeyGenerator object that generates secret keys for the specified algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new KeyGenerator object encapsulating the KeyGeneratorSpi 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 String: the standard name of the requested key algorithm. See the KeyGenerator section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
Returns
KeyGenerator the new KeyGenerator object.
Throws
NullPointerException if the specified algorithm is null.
NoSuchAlgorithmException if no Provider supports a KeyGeneratorSpi implementation for the specified algorithm.

See also:

getInstance

Added in API level 1
KeyGenerator getInstance (String algorithm, 
                String provider)

Returns a KeyGenerator object that generates secret keys for the specified algorithm.

A new KeyGenerator object encapsulating the KeyGeneratorSpi 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 String: the standard name of the requested key algorithm. See the KeyGenerator section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider String: the name of the provider.
Returns
KeyGenerator the new KeyGenerator object.
Throws
NullPointerException if the specified algorithm is null.
NoSuchAlgorithmException if a KeyGeneratorSpi 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.
IllegalArgumentException if the provider is null or empty.

See also:

getInstance

Added in API level 1
KeyGenerator getInstance (String algorithm, 
                Provider provider)

Returns a KeyGenerator object that generates secret keys for the specified algorithm.

A new KeyGenerator object encapsulating the KeyGeneratorSpi 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 String: the standard name of the requested key algorithm. See the KeyGenerator section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider Provider: the provider.
Returns
KeyGenerator the new KeyGenerator object.
Throws
NullPointerException if the specified algorithm is null.
NoSuchAlgorithmException if a KeyGeneratorSpi implementation for the specified algorithm is not available from the specified Provider object.
IllegalArgumentException if the provider is null.

See also:

getProvider

Added in API level 1
Provider getProvider ()

Returns the provider of this KeyGenerator object.

Returns
Provider the provider of this KeyGenerator object

init

Added in API level 1
void init (AlgorithmParameterSpec params, 
                SecureRandom random)

Initializes this key generator with the specified parameter set and a user-provided source of randomness.

Parameters
params AlgorithmParameterSpec: the key generation parameters
random SecureRandom: the source of randomness for this key generator
Throws
InvalidAlgorithmParameterException if params is inappropriate for this key generator

init

Added in API level 1
void init (SecureRandom random)

Initializes this key generator.

Parameters
random SecureRandom: the source of randomness for this generator

init

Added in API level 1
void init (int keysize)

Initializes this key generator for a certain 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.)

Parameters
keysize int: the keysize. This is an algorithm-specific metric, specified in number of bits.
Throws
InvalidParameterException if the keysize is wrong or not supported.

init

Added in API level 1
void init (int keysize, 
                SecureRandom random)

Initializes this key generator for a certain keysize, using a user-provided source of randomness.

Parameters
keysize int: the keysize. This is an algorithm-specific metric, specified in number of bits.
random SecureRandom: the source of randomness for this key generator
Throws
InvalidParameterException if the keysize is wrong or not supported.

init

Added in API level 1
void init (AlgorithmParameterSpec params)

Initializes this key generator with the specified parameter set.

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.)

Parameters
params AlgorithmParameterSpec: the key generation parameters
Throws
InvalidAlgorithmParameterException if the given parameters are inappropriate for this key generator
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