Added in API level 1

Summary: Ctors | Protected Ctors | Methods | Protected Methods | Inherited Methods

SecureRandom

public class SecureRandom
extends Random

java.lang.Object
↳	java.util.Random
	↳	java.security.SecureRandom

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 4086: Randomness Requirements for Security.

Many SecureRandom implementations are in the form of a pseudo-random number generator (PRNG, also known as deterministic random bits generator or DRBG), which means they use a deterministic algorithm to produce a pseudo-random sequence from a random seed. Other implementations may produce true random numbers, and yet others may use a combination of both techniques.

A caller obtains a SecureRandom instance via the no-argument constructor or one of the getInstance methods. For example:

 SecureRandom r1 = new SecureRandom();
 SecureRandom r2 = SecureRandom.getInstance("NativePRNG");
 SecureRandom r3 = SecureRandom.getInstance("DRBG",
         DrbgParameters.instantiation(128, RESEED_ONLY, null));

The third statement above returns a SecureRandom object of the specific algorithm supporting the specific instantiate parameters. The implementation's effective instantiated parameters must match this minimum request but is not necessarily the same. For example, even if the request does not require a certain feature, the actual instantiation can provide the feature. An implementation may lazily instantiate a SecureRandom until it's actually used, but the effective instantiate parameters must be determined right after it's created and getParameters() should always return the same result unchanged.

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(int) method to generate a given number of seed bytes (to seed other random number generators, for example):

 byte[] seed = random.generateSeed(20);

A newly created PRNG SecureRandom object is not seeded (except if it is created by SecureRandom(byte[])). The first call to nextBytes will force it to seed itself from an implementation- specific entropy source. This self-seeding will not occur if setSeed was previously called.

A SecureRandom can be reseeded at any time by calling the reseed or setSeed method. The reseed method reads entropy input from its entropy source to reseed itself. The setSeed method requires the caller to provide the seed.

Please note that reseed may not be supported by all SecureRandom implementations.

Some SecureRandom implementations may accept a SecureRandomParameters parameter in its nextBytes(byte[], java.security.SecureRandomParameters) and reseed(java.security.SecureRandomParameters) methods to further control the behavior of the methods.

Note: Depending on the implementation, the generateSeed, reseed and nextBytes methods may block as entropy is being gathered, for example, if the entropy source is /dev/random on various Unix-like operating systems.

Thread safety

SecureRandom objects are safe for use by multiple concurrent threads.

See also:

SecureRandomSpi
Random

Summary

Public constructors
`SecureRandom()` Constructs a secure random number generator (RNG) implementing the default random number algorithm.
`SecureRandom(byte[] seed)` Constructs a secure random number generator (RNG) implementing the default random number algorithm.

Protected constructors
`SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider)` Creates a `SecureRandom` object.

Public methods
`byte[]`	`generateSeed(int numBytes)` Returns the given number of seed bytes, computed using the seed generation algorithm that this class uses to seed itself.
`String`	`getAlgorithm()` Returns the name of the algorithm implemented by this `SecureRandom` object.
`static SecureRandom`	`getInstance(String algorithm)` Returns a `SecureRandom` object that implements the specified Random Number Generator (RNG) algorithm.
`static SecureRandom`	`getInstance(String algorithm, String provider)` Returns a `SecureRandom` object that implements the specified Random Number Generator (RNG) algorithm.
`static SecureRandom`	`getInstance(String algorithm, SecureRandomParameters params)` Returns a `SecureRandom` object that implements the specified Random Number Generator (RNG) algorithm and supports the specified `SecureRandomParameters` request.
`static SecureRandom`	`getInstance(String algorithm, Provider provider)` Returns a `SecureRandom` object that implements the specified Random Number Generator (RNG) algorithm.
`static SecureRandom`	`getInstance(String algorithm, SecureRandomParameters params, String provider)` Returns a `SecureRandom` object that implements the specified Random Number Generator (RNG) algorithm and supports the specified `SecureRandomParameters` request.
`static SecureRandom`	`getInstance(String algorithm, SecureRandomParameters params, Provider provider)` Returns a `SecureRandom` object that implements the specified Random Number Generator (RNG) algorithm and supports the specified `SecureRandomParameters` request.
`static SecureRandom`	`getInstanceStrong()` Returns a `SecureRandom` object.
`SecureRandomParameters`	`getParameters()` Returns the effective `SecureRandomParameters` for this `SecureRandom` instance.
`final Provider`	`getProvider()` Returns the provider of this `SecureRandom` object.
`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.
`void`	`nextBytes(byte[] bytes, SecureRandomParameters params)` Generates a user-specified number of random bytes with additional parameters.
`void`	`nextBytes(byte[] bytes)` Generates a user-specified number of random bytes.
`void`	`reseed(SecureRandomParameters params)` Reseeds this `SecureRandom` with entropy input read from its entropy source with additional parameters.
`void`	`reseed()` Reseeds this `SecureRandom` with entropy input read from its entropy source.
`void`	`setSeed(long seed)` Reseeds this random object, using the eight bytes contained in the given `long seed`.
`void`	`setSeed(byte[] seed)` Reseeds this random object with the given seed.
`String`	`toString()` Returns a Human-readable string representation of this `SecureRandom`.

Protected methods
`final int`	`next(int numBits)` Generates an integer containing the user-specified number of pseudo-random bits (right justified, with leading zeros).

Inherited methods

From class


        
          java.util.Random

`DoubleStream`	`doubles(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandom `double` values, each between zero (inclusive) and one (exclusive).
`DoubleStream`	`doubles()` Returns an effectively unlimited stream of pseudorandom `double` values, each between zero (inclusive) and one (exclusive).
`DoubleStream`	`doubles(double randomNumberOrigin, double randomNumberBound)` Returns an effectively unlimited stream of pseudorandom `double` values, each conforming to the given origin (inclusive) and bound (exclusive).
`DoubleStream`	`doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandom `double` values, each conforming to the given origin (inclusive) and bound (exclusive).
`static Random`	`from(RandomGenerator generator)` Returns an instance of `Random` that delegates method calls to the `RandomGenerator` argument.
`IntStream`	`ints(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandom `int` values.
`IntStream`	`ints(int randomNumberOrigin, int randomNumberBound)` Returns an effectively unlimited stream of pseudorandom `int` values, each conforming to the given origin (inclusive) and bound (exclusive).
`IntStream`	`ints(long streamSize, int randomNumberOrigin, int randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandom `int` values, each conforming to the given origin (inclusive) and bound (exclusive).
`IntStream`	`ints()` Returns an effectively unlimited stream of pseudorandom `int` values.
`LongStream`	`longs()` Returns an effectively unlimited stream of pseudorandom `long` values.
`LongStream`	`longs(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandom `long` values.
`LongStream`	`longs(long randomNumberOrigin, long randomNumberBound)` Returns an effectively unlimited stream of pseudorandom `long` values, each conforming to the given origin (inclusive) and bound (exclusive).
`LongStream`	`longs(long streamSize, long randomNumberOrigin, long randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandom `long`, each conforming to the given origin (inclusive) and bound (exclusive).
`int`	`next(int bits)` Generates the next pseudorandom number.
`boolean`	`nextBoolean()` Returns the next pseudorandom, uniformly distributed `boolean` value from this random number generator's sequence.
`void`	`nextBytes(byte[] bytes)` Generates random bytes and places them into a user-supplied byte array.
`double`	`nextDouble()` Returns the next pseudorandom, uniformly distributed `double` value between `0.0` and `1.0` from this random number generator's sequence.
`float`	`nextFloat()` Returns the next pseudorandom, uniformly distributed `float` value between `0.0` and `1.0` from this random number generator's sequence.
`double`	`nextGaussian()` Returns the next pseudorandom, Gaussian ("normally") distributed `double` value with mean `0.0` and standard deviation `1.0` from this random number generator's sequence.
`int`	`nextInt()` Returns the next pseudorandom, uniformly distributed `int` value from this random number generator's sequence.
`int`	`nextInt(int bound)` Returns a pseudorandom, uniformly distributed `int` value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.
`long`	`nextLong()` Returns the next pseudorandom, uniformly distributed `long` value from this random number generator's sequence.
`void`	`setSeed(long seed)` Sets or updates the seed of this random number generator using the provided `long` seed value (optional operation).

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface


        
          java.util.random.RandomGenerator

`default DoubleStream`	`doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `double` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default DoubleStream`	`doubles(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `double` values.
`default DoubleStream`	`doubles()` Returns an effectively unlimited stream of pseudorandomly chosen `double` values.
`default DoubleStream`	`doubles(double randomNumberOrigin, double randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `double` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`static RandomGenerator`	`getDefault()` Returns a `RandomGenerator` meeting the minimal requirement of having an algorithm whose state bits are greater than or equal 64.
`default IntStream`	`ints(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `int` values.
`default IntStream`	`ints(int randomNumberOrigin, int randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `int` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default IntStream`	`ints()` Returns an effectively unlimited stream of pseudorandomly chosen `int` values.
`default IntStream`	`ints(long streamSize, int randomNumberOrigin, int randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `int` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default boolean`	`isDeprecated()` Return true if the implementation of RandomGenerator (algorithm) has been marked for deprecation.
`default LongStream`	`longs(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `long` values.
`default LongStream`	`longs()` Returns an effectively unlimited stream of pseudorandomly chosen `long` values.
`default LongStream`	`longs(long randomNumberOrigin, long randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `long` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default LongStream`	`longs(long streamSize, long randomNumberOrigin, long randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `long` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default boolean`	`nextBoolean()` Returns a pseudorandomly chosen `boolean` value.
`default void`	`nextBytes(byte[] bytes)` Fills a user-supplied byte array with generated byte values pseudorandomly chosen uniformly from the range of values between -128 (inclusive) and 127 (inclusive).
`default double`	`nextDouble()` Returns a pseudorandom `double` value between zero (inclusive) and one (exclusive).
`default double`	`nextDouble(double bound)` Returns a pseudorandomly chosen `double` value between zero (inclusive) and the specified bound (exclusive).
`default double`	`nextDouble(double origin, double bound)` Returns a pseudorandomly chosen `double` value between the specified origin (inclusive) and the specified bound (exclusive).
`default double`	`nextExponential()` Returns a nonnegative `double` value pseudorandomly chosen from an exponential distribution whose mean is 1.
`default float`	`nextFloat(float origin, float bound)` Returns a pseudorandomly chosen `float` value between the specified origin (inclusive) and the specified bound (exclusive).
`default float`	`nextFloat()` Returns a pseudorandom `float` value between zero (inclusive) and one (exclusive).
`default float`	`nextFloat(float bound)` Returns a pseudorandomly chosen `float` value between zero (inclusive) and the specified bound (exclusive).
`default double`	`nextGaussian(double mean, double stddev)` Returns a `double` value pseudorandomly chosen from a Gaussian (normal) distribution with a mean and standard deviation specified by the arguments.
`default double`	`nextGaussian()` Returns a `double` value pseudorandomly chosen from a Gaussian (normal) distribution whose mean is 0 and whose standard deviation is 1.
`default int`	`nextInt(int origin, int bound)` Returns a pseudorandomly chosen `int` value between the specified origin (inclusive) and the specified bound (exclusive).
`default int`	`nextInt()` Returns a pseudorandomly chosen `int` value.
`default int`	`nextInt(int bound)` Returns a pseudorandomly chosen `int` value between zero (inclusive) and the specified bound (exclusive).
`default long`	`nextLong(long origin, long bound)` Returns a pseudorandomly chosen `long` value between the specified origin (inclusive) and the specified bound (exclusive).
`default long`	`nextLong(long bound)` Returns a pseudorandomly chosen `long` value between zero (inclusive) and the specified bound (exclusive).
`abstract long`	`nextLong()` Returns a pseudorandomly chosen `long` value.
`static RandomGenerator`	`of(String name)` Returns an instance of `RandomGenerator` that utilizes the `name` algorithm.

Public constructors

SecureRandom

Added in API level 1

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() method.

See the SecureRandom section in the Java Security Standard Algorithm Names Specification for information about standard RNG algorithm names.

SecureRandom

Added in API level 1

public SecureRandom (byte[] seed)

Constructs a secure random number generator (RNG) implementing the default random number algorithm. The SecureRandom instance is seeded with the specified seed bytes.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

See the SecureRandom section in the Java Security Standard Algorithm Names Specification for information about standard RNG algorithm names.

Parameters
`seed`	`byte`: the seed.

Protected constructors

SecureRandom

Added in API level 1

protected SecureRandom (SecureRandomSpi secureRandomSpi, 
                Provider provider)

Creates a SecureRandom object.

Parameters
`secureRandomSpi`	`SecureRandomSpi`: the `SecureRandom` implementation.
`provider`	`Provider`: the provider.

Public methods

generateSeed

Added in API level 1

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. This call may be used to seed other random number generators.

Parameters
`numBytes`	`int`: the number of seed bytes to generate.

Returns
`byte[]`	the seed bytes.

Throws
`IllegalArgumentException`	if `numBytes` is negative

getAlgorithm

Added in API level 1

public String getAlgorithm ()

Returns the name of the algorithm implemented by this SecureRandom object.

Returns
`String`	the name of the algorithm or `unknown` if the algorithm name cannot be determined.

getInstance

Added in API level 1

public static SecureRandom getInstance (String algorithm)

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() 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 than the order of providers returned by Security.getProviders().

Parameters
`algorithm`	`String`: the name of the RNG algorithm. See the `SecureRandom` section in the Java Security Standard Algorithm Names Specification for information about standard RNG algorithm names.

Returns
`SecureRandom`	the new `SecureRandom` object

Throws
`NoSuchAlgorithmException`	if no `Provider` supports a `SecureRandomSpi` implementation for the specified algorithm
`NullPointerException`	if `algorithm` is `null`

See also:

Provider

getInstance

Added in API level 1

public static SecureRandom getInstance (String algorithm, 
                String provider)

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() method.

Parameters
`algorithm`	`String`: the name of the RNG algorithm. See the `SecureRandom` section in the Java Security Standard Algorithm Names Specification for information about standard RNG algorithm names.
`provider`	`String`: the name of the provider.

Returns
`SecureRandom`	the new `SecureRandom` object

Throws
`IllegalArgumentException`	if the provider name is `null` or empty
`NoSuchAlgorithmException`	if a `SecureRandomSpi` 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`

See also:

Provider

getInstance

Added in API level 35

public static SecureRandom getInstance (String algorithm, 
                SecureRandomParameters params)

Returns a SecureRandom object that implements the specified Random Number Generator (RNG) algorithm and supports the specified SecureRandomParameters request.

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 property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned by Security.getProviders().

Parameters
`algorithm`	`String`: the name of the RNG algorithm. See the `SecureRandom` section in the Java Security Standard Algorithm Names Specification for information about standard RNG algorithm names.
`params`	`SecureRandomParameters`: the `SecureRandomParameters` the newly created `SecureRandom` object must support.

Returns
`SecureRandom`	the new `SecureRandom` object

Throws
`IllegalArgumentException`	if the specified params is `null`
`NoSuchAlgorithmException`	if no Provider supports a `SecureRandomSpi` implementation for the specified algorithm and parameters
`NullPointerException`	if `algorithm` is `null`

See also:

Provider

getInstance

Added in API level 1

public static SecureRandom getInstance (String algorithm, 
                Provider provider)

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.

Parameters
`algorithm`	`String`: the name of the RNG algorithm. See the `SecureRandom` section in the Java Security Standard Algorithm Names Specification for information about standard RNG algorithm names.
`provider`	`Provider`: the provider.

Returns
`SecureRandom`	the new `SecureRandom` object

Throws
`IllegalArgumentException`	if the specified provider is `null`
`NoSuchAlgorithmException`	if a `SecureRandomSpi` implementation for the specified algorithm is not available from the specified `Provider` object
`NullPointerException`	if `algorithm` is `null`

See also:

Provider

getInstance

Added in API level 35

public static SecureRandom getInstance (String algorithm, 
                SecureRandomParameters params, 
                String provider)

Returns a SecureRandom object that implements the specified Random Number Generator (RNG) algorithm and supports the specified SecureRandomParameters request.

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() method.

Parameters
`algorithm`	`String`: the name of the RNG algorithm. See the `SecureRandom` section in the Java Security Standard Algorithm Names Specification for information about standard RNG algorithm names.
`params`	`SecureRandomParameters`: the `SecureRandomParameters` the newly created `SecureRandom` object must support.
`provider`	`String`: the name of the provider.

Returns
`SecureRandom`	the new `SecureRandom` object

Throws
`IllegalArgumentException`	if the provider name is `null` or empty, or params is `null`
`NoSuchAlgorithmException`	if the specified provider does not support a `SecureRandomSpi` implementation for the specified algorithm and parameters
`NoSuchProviderException`	if the specified provider is not registered in the security provider list
`NullPointerException`	if `algorithm` is `null`

See also:

Provider

getInstance

Added in API level 35

public static SecureRandom getInstance (String algorithm, 
                SecureRandomParameters params, 
                Provider provider)

Returns a SecureRandom object that implements the specified Random Number Generator (RNG) algorithm and supports the specified SecureRandomParameters request.

Parameters
`algorithm`	`String`: the name of the RNG algorithm. See the `SecureRandom` section in the Java Security Standard Algorithm Names Specification for information about standard RNG algorithm names.
`params`	`SecureRandomParameters`: the `SecureRandomParameters` the newly created `SecureRandom` object must support.
`provider`	`Provider`: the provider.

Returns
`SecureRandom`	the new `SecureRandom` object

Throws
`IllegalArgumentException`	if the specified provider or params is `null`
`NoSuchAlgorithmException`	if the specified provider does not support a `SecureRandomSpi` implementation for the specified algorithm and parameters
`NullPointerException`	if `algorithm` is `null`

See also:

Provider

getInstanceStrong

Added in API level 26

public static SecureRandom getInstanceStrong ()

Returns a SecureRandom object. In Android this is equivalent to get a SHA1PRNG from AndroidOpenSSL. Some situations require strong random values, such as when creating high-value/long-lived secrets like RSA public/private keys. To help guide applications in selecting a suitable strong SecureRandom implementation, Java distributions include a list of known strong SecureRandom implementations in the securerandom.strongAlgorithms Security property.

Every implementation of the Java platform is required to support at least one strong SecureRandom implementation.

Returns
`SecureRandom`	a strong `SecureRandom` implementation

Throws
`NoSuchAlgorithmException`	if no algorithm is available

See also:

Security.getProperty(String)

getParameters

Added in API level 35

public SecureRandomParameters getParameters ()

Returns the effective SecureRandomParameters for this SecureRandom instance.

The returned value can be different from the SecureRandomParameters object passed into a getInstance method, but it cannot change during the lifetime of this SecureRandom object.

A caller can use the returned value to find out what features this SecureRandom supports.

Returns
`SecureRandomParameters`	the effective `SecureRandomParameters` parameters, or `null` if no parameters were used.

See also:

SecureRandomSpi

getProvider

Added in API level 1

public final Provider getProvider ()

Returns the provider of this SecureRandom object.

Returns
`Provider`	the provider of this `SecureRandom` object.

getSeed

Added in API level 1

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. 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`	`int`: the number of seed bytes to generate.

Returns
`byte[]`	the seed bytes.

Throws
`IllegalArgumentException`	if `numBytes` is negative

See also:

setSeed(byte)

nextBytes

Added in API level 35

public void nextBytes (byte[] bytes, 
                SecureRandomParameters params)

Generates a user-specified number of random bytes with additional parameters.

Parameters
`bytes`	`byte`: the array to be filled in with random bytes
`params`	`SecureRandomParameters`: additional parameters

Throws
`NullPointerException`	if `bytes` is null
`UnsupportedOperationException`	if the underlying provider implementation has not overridden this method
`IllegalArgumentException`	if `params` is `null`, illegal or unsupported by this `SecureRandom`

nextBytes

Added in API level 1

public void nextBytes (byte[] bytes)

Generates a user-specified number of random bytes.

Parameters
`bytes`	`byte`: the array to be filled in with random bytes.

reseed

Added in API level 35

public void reseed (SecureRandomParameters params)

Reseeds this SecureRandom with entropy input read from its entropy source with additional parameters.

Note that entropy is obtained from an entropy source. While some data in params may contain entropy, its main usage is to provide diversity.

Parameters
`params`	`SecureRandomParameters`: extra parameters

Throws
`UnsupportedOperationException`	if the underlying provider implementation has not overridden this method.
`IllegalArgumentException`	if `params` is `null`, illegal or unsupported by this `SecureRandom`

reseed

Added in API level 35

public void reseed ()

Reseeds this SecureRandom with entropy input read from its entropy source.

Throws
`UnsupportedOperationException`	if the underlying provider implementation has not overridden this method.

setSeed

Added in API level 1

public void setSeed (long seed)

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`	`long`: the seed.

See also:

getSeed(int)

setSeed

Added in API level 1

public void setSeed (byte[] seed)

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

A PRNG SecureRandom will not seed itself automatically if setSeed is called before any nextBytes or reseed calls. The caller should make sure that the seed argument contains enough entropy for the security of this SecureRandom.

Parameters
`seed`	`byte`: the seed.

See also:

getSeed(int)

toString

Added in API level 1

public String toString ()

Returns a Human-readable string representation of this SecureRandom.

Returns
`String`	the string representation

Protected methods

Added in API level 1

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).

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

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