java.security
Class SecureRandom

java.lang.Object
  |
  +--java.util.Random
        |
        +--java.security.SecureRandom

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

ESecureRandom

public class SecureRandom

extends Random

Untamed:

See Also:

Serialized Form

Field Summary

private long	counter
private MessageDigest	digest
private Provider	provider The provider.
private byte[]	randomBytes
private int	randomBytesUsed
private SecureRandomSpi	secureRandomSpi The provider implementation.
private static SecureRandom	seedGenerator
(package private) static long	serialVersionUID
private byte[]	state

Fields inherited from class java.util.Random

Constructor Summary

	SecureRandom() Enabled:
	SecureRandom(byte[] seed) Enabled:
protected	SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider) Creates a SecureRandom object.

Method Summary

byte[]	generateSeed(int numBytes) Enabled: Returns the given number of seed bytes, computed using the seed generation algorithm that this class uses to seed itself.
static SecureRandom	getInstance(String algorithm) Enabled: Generates a SecureRandom object that implements the specified Pseudo Random Number Generator (PRNG) algorithm.
static SecureRandom	getInstance(String algorithm, Provider provider) Enabled: Generates a SecureRandom object for the specified PRNG algorithm, as supplied from the specified provider, if such a PRNG implementation is available from the provider.
static SecureRandom	getInstance(String algorithm, String provider) Enabled: Generates a SecureRandom object for the specified PRNG algorithm, as supplied from the specified provider, if such a PRNG implementation is available from the provider.
private static String	getPrngAlgorithm() Gets a default PRNG algorithm by looking through all registered providers.
Provider	getProvider() Enabled: Returns the provider of this SecureRandom object.
(package private) SecureRandomSpi	getSecureRandomSpi() Returns the SecureRandomSpi of this SecureRandom object.
static byte[]	getSeed(int numBytes) Enabled: Returns the given number of seed bytes, computed using the seed generation algorithm that this class uses to seed itself.
private static byte[]	longToByteArray(long l) Helper function to convert a long into a byte array (least significant byte first).
protected int	next(int numBits) Generates an integer containing the user-specified number of pseudo-random bits (right justified, with leading zeros).
void	nextBytes(byte[] bytes) Enabled: Generates a user-specified number of random bytes.
void	setSeed(byte[] seed) Enabled: Reseeds this random object.
void	setSeed(long seed) Enabled: Reseeds this random object, using the eight bytes contained in the given long seed.

Methods inherited from class java.util.Random

nextBoolean, nextDouble, nextFloat, nextGaussian, nextInt, nextInt, nextLong

Methods inherited from class java.lang.Object

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

Field Detail

provider

private Provider provider

The provider.

Since:

1.2

secureRandomSpi

private SecureRandomSpi secureRandomSpi

The provider implementation.

Since:

1.2

seedGenerator

private static SecureRandom seedGenerator

serialVersionUID

static final long serialVersionUID

state

private byte[] state

digest

private MessageDigest digest

randomBytes

private byte[] randomBytes

randomBytesUsed

private int randomBytesUsed

counter

private long counter

Constructor Detail

SecureRandom

public SecureRandom()

Enabled:

By using this constructor, the caller obtains a SecureRandom object containing the implementation from the highest-priority installed provider that has a SecureRandom implementation.

Note that this instance of SecureRandom has not been seeded. A call to the setSeed method will seed the SecureRandom object. If a call is not made to setSeed, the first call to the nextBytes method will force the SecureRandom object to seed itself.

This constructor is provided for backwards compatibility. The caller is encouraged to use one of the alternative getInstance methods to obtain a SecureRandom object.

SecureRandom

public SecureRandom(byte[] seed)

Enabled:

By using this constructor, the caller obtains a SecureRandom object containing the implementation from the highest-priority installed provider that has a SecureRandom implementation. This constructor uses a user-provided seed in preference to the self-seeding algorithm referred to in the empty constructor description. It may be preferable to the empty constructor if the caller has access to high-quality random bytes from some physical device (for example, a radiation detector or a noisy diode).

This constructor is provided for backwards compatibility. The caller is encouraged to use one of the alternative getInstance methods to obtain a SecureRandom object, and then to call the setSeed method to seed it.

Parameters:

seed - the seed.

SecureRandom

protected SecureRandom(SecureRandomSpi secureRandomSpi,
                       Provider provider)

Creates a SecureRandom object.

Parameters:

secureRandomSpi - the SecureRandom implementation.

provider - the provider.

Method Detail

getInstance

public static SecureRandom getInstance(String algorithm)
                                throws NoSuchAlgorithmException

Enabled: Generates a SecureRandom object that implements the specified Pseudo Random Number Generator (PRNG) algorithm. If the default provider package provides an implementation of the requested PRNG, an instance of SecureRandom containing that implementation is returned. If the PRNG is not available in the default package, other packages are searched.

Note that the returned instance of SecureRandom has not been seeded. A call to the setSeed method will seed the SecureRandom object. If a call is not made to setSeed, the first call to the nextBytes method will force the SecureRandom object to seed itself.

Parameters:

algorithm - the name of the PRNG algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard PRNG algorithm names.

Returns:

the new SecureRandom object.

NoSuchAlgorithmException

Since:

1.2

getInstance

public static SecureRandom getInstance(String algorithm,
                                       String provider)
                                throws NoSuchAlgorithmException,
                                       NoSuchProviderException

Enabled: Generates a SecureRandom object for the specified PRNG algorithm, as supplied from the specified provider, if such a PRNG implementation is available from the provider.

Note that the returned instance of SecureRandom has not been seeded. A call to the setSeed method will seed the SecureRandom object. If a call is not made to setSeed, the first call to the nextBytes method will force the SecureRandom object to seed itself.

Parameters:

algorithm - the name of the PRNG algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard PRNG algorithm names.

provider - the name of the provider.

Returns:

the new SecureRandom object.

NoSuchAlgorithmException

NoSuchProviderException

Since:

1.2

See Also:

Provider

getInstance

public static SecureRandom getInstance(String algorithm,
                                       Provider provider)
                                throws NoSuchAlgorithmException

Enabled: Generates a SecureRandom object for the specified PRNG algorithm, as supplied from the specified provider, if such a PRNG implementation is available from the provider. Note: the provider doesn't have to be registered.

Note that the returned instance of SecureRandom has not been seeded. A call to the setSeed method will seed the SecureRandom object. If a call is not made to setSeed, the first call to the nextBytes method will force the SecureRandom object to seed itself.

Parameters:

algorithm - the name of the PRNG algorithm. See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard PRNG algorithm names.

provider - the provider.

Returns:

the new SecureRandom object.

NoSuchAlgorithmException

Since:

1.4

See Also:

Provider

getSecureRandomSpi

SecureRandomSpi getSecureRandomSpi()

Returns the SecureRandomSpi of this SecureRandom object.

getProvider

public final Provider getProvider()

Enabled: Returns the provider of this SecureRandom object.

Returns:

the provider of this SecureRandom object.

setSeed

public void setSeed(byte[] seed)

Enabled: Reseeds this random object. The given seed supplements, rather than replaces, the existing seed. Thus, repeated calls are guaranteed never to reduce randomness.

Parameters:

seed - the seed.

See Also:

getSeed(int)

setSeed

public void setSeed(long seed)

Enabled: Reseeds this random object, using the eight bytes contained in the given long seed. The given seed supplements, rather than replaces, the existing seed. Thus, repeated calls are guaranteed never to reduce randomness.

This method is defined for compatibility with java.util.Random.

Overrides:

setSeed in class Random

Parameters:

seed - the seed.

See Also:

getSeed(int)

nextBytes

public void nextBytes(byte[] bytes)

Enabled: Generates a user-specified number of random bytes. This method is used as the basis of all random entities returned by this class (except seed bytes).

Overrides:

nextBytes in class Random

Parameters:

bytes - the array to be filled in with random bytes.

next

protected final int next(int numBits)

Generates an integer containing the user-specified number of pseudo-random bits (right justified, with leading zeros). This method overrides a java.util.Random method, and serves to provide a source of random bits to all of the methods inherited from that class (for example, nextInt, nextLong, and nextFloat).

Overrides:

next in class Random

Parameters:

numBits - number of pseudo-random bits to be generated, where 0 <= numBits <= 32.

Returns:

an int containing the user-specified number of pseudo-random bits (right justified, with leading zeros).

getSeed

public static byte[] getSeed(int numBytes)

Enabled: Returns the given number of seed bytes, computed using the seed generation algorithm that this class uses to seed itself. This call may be used to seed other random number generators.

This method is only included for backwards compatibility. The caller is encouraged to use one of the alternative getInstance methods to obtain a SecureRandom object, and then call the generateSeed method to obtain seed bytes from that object.

Parameters:

numBytes - the number of seed bytes to generate.

Returns:

the seed bytes.

See Also:

setSeed(byte[])

generateSeed

public byte[] generateSeed(int numBytes)

Enabled: Returns the given number of seed bytes, computed using the seed generation algorithm that this class uses to seed itself. This call may be used to seed other random number generators.

Parameters:

numBytes - the number of seed bytes to generate.

Returns:

the seed bytes.

longToByteArray

private static byte[] longToByteArray(long l)

Helper function to convert a long into a byte array (least significant byte first).

getPrngAlgorithm

private static String getPrngAlgorithm()

Gets a default PRNG algorithm by looking through all registered providers. Returns the first PRNG algorithm of the first provider that has registered a SecureRandom implementation, or null if none of the registered providers supplies a SecureRandom implementation.