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| java.lang.Object
 java.util.Random
java.security.SecureRandom
| SecureRandom | | public class SecureRandom extends java.util.Random (Code) | | This class provides a cryptographically strong random number
generator (RNG).
A cryptographically strong random number
minimally complies with the statistical random number generator tests
specified in
FIPS 140-2, Security Requirements for Cryptographic Modules,
section 4.9.1.
Additionally, SecureRandom must produce non-deterministic output.
Therefore any seed material passed to a SecureRandom object must be
unpredictable, and all SecureRandom output sequences must be
cryptographically strong, as described in
RFC 1750: Randomness Recommendations for Security.
A caller obtains a SecureRandom instance via the
no-argument constructor or one of the getInstance methods:
SecureRandom random = new SecureRandom();
Many SecureRandom implementations are in the form of a pseudo-random
number generator (PRNG), which means they use a deterministic algorithm
to produce a pseudo-random sequence from a true random seed.
Other implementations may produce true random numbers,
and yet others may use a combination of both techniques.
Typical callers of SecureRandom invoke the following methods
to retrieve random bytes:
SecureRandom random = new SecureRandom();
byte bytes[] = new byte[20];
random.nextBytes(bytes);
Callers may also invoke the generateSeed method
to generate a given number of seed bytes (to seed other random number
generators, for example):
byte seed[] = random.generateSeed(20);
See Also: java.security.SecureRandomSpi
See Also: java.util.Random
version:
1.62, 07/12/07
author:
Benjamin Renaud
author:
Josh Bloch |
| Constructor Summary | |
| public | SecureRandom()
Constructs a secure random number generator (RNG) implementing the
default random number algorithm.
This constructor traverses the list of registered security Providers,
starting with the most preferred Provider.
A new SecureRandom object encapsulating the
SecureRandomSpi implementation from the first
Provider that supports a SecureRandom (RNG) algorithm is returned.
If none of the Providers support a RNG algorithm,
then an implementation-specific default is returned.
Note that the list of registered providers may be retrieved via
the
Security.getProviders Security.getProviders() method.
See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard RNG algorithm names.
The returned SecureRandom object has not been seeded. | | public | SecureRandom(byte seed)
Constructs a secure random number generator (RNG) implementing the
default random number algorithm. | | protected | SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider)
Creates a SecureRandom object. |
| Method Summary | |
| public byte[] | generateSeed(int numBytes)
Returns the given number of seed bytes, computed using the seed
generation algorithm that this class uses to seed itself. | | public String | getAlgorithm()
Returns the name of the algorithm implemented by this SecureRandom
object. | | public static SecureRandom | getInstance(String algorithm)
Returns a SecureRandom object that implements the specified
Random Number Generator (RNG) algorithm. | | public static SecureRandom | getInstance(String algorithm, String provider)
Returns a SecureRandom object that implements the specified
Random Number Generator (RNG) algorithm. | | public static SecureRandom | getInstance(String algorithm, Provider provider)
Returns a SecureRandom object that implements the specified
Random Number Generator (RNG) algorithm. | | final public Provider | getProvider()
Returns the provider of this SecureRandom object. | | SecureRandomSpi | getSecureRandomSpi()
Returns the SecureRandomSpi of this SecureRandom object. | | public static byte[] | getSeed(int numBytes)
Returns the given number of seed bytes, computed using the seed
generation algorithm that this class uses to seed itself. | | final protected int | next(int numBits)
Generates an integer containing the user-specified number of
pseudo-random bits (right justified, with leading zeros). | | public synchronized void | nextBytes(byte[] bytes)
Generates a user-specified number of random bytes.
If a call to setSeed had not occurred previously,
the first call to this method forces this SecureRandom object
to seed itself. | | public synchronized void | setSeed(byte[] seed)
Reseeds this random object. | | public void | setSeed(long seed)
Reseeds this random object, using the eight bytes contained
in the given long seed. |
| serialVersionUID | | final static long serialVersionUID(Code) | | |
| SecureRandom | | public SecureRandom()(Code) | | Constructs a secure random number generator (RNG) implementing the
default random number algorithm.
This constructor traverses the list of registered security Providers,
starting with the most preferred Provider.
A new SecureRandom object encapsulating the
SecureRandomSpi implementation from the first
Provider that supports a SecureRandom (RNG) algorithm is returned.
If none of the Providers support a RNG algorithm,
then an implementation-specific default is returned.
Note that the list of registered providers may be retrieved via
the
Security.getProviders Security.getProviders() method.
See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard RNG algorithm names.
The returned SecureRandom object has not been seeded. To seed the
returned object, call the setSeed method.
If setSeed is not called, the first call to
nextBytes will force the SecureRandom object to seed itself.
This self-seeding will not occur if setSeed was
previously called.
|
| SecureRandom | | public SecureRandom(byte seed)(Code) | | Constructs a secure random number generator (RNG) implementing the
default random number algorithm.
The SecureRandom instance is seeded with the specified seed bytes.
This constructor traverses the list of registered security Providers,
starting with the most preferred Provider.
A new SecureRandom object encapsulating the
SecureRandomSpi implementation from the first
Provider that supports a SecureRandom (RNG) algorithm is returned.
If none of the Providers support a RNG algorithm,
then an implementation-specific default is returned.
Note that the list of registered providers may be retrieved via
the
Security.getProviders Security.getProviders() method.
See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard RNG algorithm names.
Parameters:
seed - the seed. |
| SecureRandom | | protected SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider)(Code) | | Creates a SecureRandom object.
Parameters:
secureRandomSpi - the SecureRandom implementation.
Parameters:
provider - the provider. |
| generateSeed | | public byte[] generateSeed(int numBytes)(Code) | | 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. the seed bytes. |
| getAlgorithm | | public String getAlgorithm()(Code) | | Returns the name of the algorithm implemented by this SecureRandom
object.
the name of the algorithm or unknownif the algorithm name cannot be determined.
since:
1.5 |
| getInstance | | public static SecureRandom getInstance(String algorithm) throws NoSuchAlgorithmException(Code) | | Returns a SecureRandom object that implements the specified
Random Number Generator (RNG) algorithm.
This method traverses the list of registered security Providers,
starting with the most preferred Provider.
A new SecureRandom object encapsulating the
SecureRandomSpi 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 Security.getProviders() method.
The returned SecureRandom object has not been seeded. To seed the
returned object, call the setSeed method.
If setSeed is not called, the first call to
nextBytes will force the SecureRandom object to seed itself.
This self-seeding will not occur if setSeed was
previously called.
Parameters:
algorithm - the name of the RNG algorithm.See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard RNG algorithm names. the new SecureRandom object.
exception:
NoSuchAlgorithmException - if no Provider supports aSecureRandomSpi implementation for thespecified algorithm.
See Also: Provider
since:
1.2 |
| getInstance | | public static SecureRandom getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException(Code) | | Returns a SecureRandom object that implements the specified
Random Number Generator (RNG) algorithm.
A new SecureRandom object encapsulating the
SecureRandomSpi 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 Security.getProviders() method.
The returned SecureRandom object has not been seeded. To seed the
returned object, call the setSeed method.
If setSeed is not called, the first call to
nextBytes will force the SecureRandom object to seed itself.
This self-seeding will not occur if setSeed was
previously called.
Parameters:
algorithm - the name of the RNG algorithm.See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard RNG algorithm names.
Parameters:
provider - the name of the provider. the new SecureRandom object.
exception:
NoSuchAlgorithmException - if a SecureRandomSpiimplementation for the specified algorithm is notavailable from the specified provider.
exception:
NoSuchProviderException - if the specified provider is notregistered in the security provider list.
exception:
IllegalArgumentException - if the provider name is nullor empty.
See Also: Provider
since:
1.2 |
| getInstance | | public static SecureRandom getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException(Code) | | Returns a SecureRandom object that implements the specified
Random Number Generator (RNG) algorithm.
A new SecureRandom object encapsulating the
SecureRandomSpi implementation from the specified Provider
object is returned. Note that the specified Provider object
does not have to be registered in the provider list.
The returned SecureRandom object has not been seeded. To seed the
returned object, call the setSeed method.
If setSeed is not called, the first call to
nextBytes will force the SecureRandom object to seed itself.
This self-seeding will not occur if setSeed was
previously called.
Parameters:
algorithm - the name of the RNG algorithm.See Appendix A in the Java Cryptography Architecture API Specification & Reference for information about standard RNG algorithm names.
Parameters:
provider - the provider. the new SecureRandom object.
exception:
NoSuchAlgorithmException - if a SecureRandomSpiimplementation for the specified algorithm is not availablefrom the specified Provider object.
exception:
IllegalArgumentException - if the specified provider is null.
See Also: Provider
since:
1.4 |
| getProvider | | final public Provider getProvider()(Code) | | Returns the provider of this SecureRandom object.
the provider of this SecureRandom object. |
| getSecureRandomSpi | | SecureRandomSpi getSecureRandomSpi()(Code) | | Returns the SecureRandomSpi of this SecureRandom object.
|
| getSeed | | public static byte[] getSeed(int numBytes)(Code) | | 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. the seed bytes.
See Also: SecureRandom.setSeed |
| next | | final protected int next(int numBits)(Code) | | 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).
Parameters:
numBits - number of pseudo-random bits to be generated, where0 <= numBits <= 32. an int containing the user-specified numberof pseudo-random bits (right justified, with leading zeros). |
| nextBytes | | public synchronized void nextBytes(byte[] bytes)(Code) | | Generates a user-specified number of random bytes.
If a call to setSeed had not occurred previously,
the first call to this method forces this SecureRandom object
to seed itself. This self-seeding will not occur if
setSeed was previously called.
Parameters:
bytes - the array to be filled in with random bytes. |
| setSeed | | public synchronized void setSeed(byte[] seed)(Code) | | 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: SecureRandom.getSeed |
| setSeed | | public void setSeed(long seed)(Code) | | 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.
Parameters:
seed - the seed.
See Also: SecureRandom.getSeed |
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