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Android Reference

SecureRandom

java.security

Class SecureRandom

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

All Implemented Interfaces:

Serializable
```
public class SecureRandom
extends Random
```
This class generates cryptographically secure pseudo-random numbers.
Supported Algorithms
- SHA1PRNG: Based on SHA-1. Not guaranteed to be compatible with the SHA1PRNG algorithm on the reference implementation.
The default algorithm is defined by the first SecureRandomSpi provider found in the VM's installed security providers. Use Security to install custom SecureRandomSpi providers.
Seeding SecureRandom may be insecure
A seed is an array of bytes used to bootstrap random number generation. To produce cryptographically secure random numbers, both the seed and the algorithm must be secure.
By default, instances of this class will generate an initial seed using an internal entropy source, such as /dev/urandom. This seed is unpredictable and appropriate for secure use.
You may alternatively specify the initial seed explicitly with the seeded constructor or by calling setSeed(byte[]) before any random numbers have been generated. Specifying a fixed seed will cause the instance to return a predictable sequence of numbers. This may be useful for testing but it is not appropriate for secure use.
It is dangerous to seed SecureRandom with the current time because that value is more predictable to an attacker than the default seed.
Calling setSeed(byte[]) on a SecureRandom after it has been used to generate random numbers (ie. calling nextBytes(byte[])) will supplement the existing seed. This does not cause the instance to return a predictable numbers, nor does it harm the security of the numbers generated.
See Also:
Serialized Form

Constructor Summary

Constructors
Modifier	Constructor and Description
	`SecureRandom()` Constructs a new `SecureRandom` that uses the default algorithm.
	`SecureRandom(byte[] seed)` Constructs a new seeded `SecureRandom` that uses the default algorithm.
`protected`	`SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider)` Constructs a new instance of `SecureRandom` using the given implementation from the specified provider.

Method Summary

Methods
Modifier and Type	Method and Description
`byte[]`	`generateSeed(int numBytes)` Generates and returns the specified number of seed bytes, computed using the seed generation algorithm used by this `SecureRandom`.
`String`	`getAlgorithm()` Returns the name of the algorithm of this `SecureRandom`.
`static SecureRandom`	`getInstance(String algorithm)` Returns a new instance of `SecureRandom` that utilizes the specified algorithm.
`static SecureRandom`	`getInstance(String algorithm, Provider provider)` Returns a new instance of `SecureRandom` that utilizes the specified algorithm from the specified provider.
`static SecureRandom`	`getInstance(String algorithm, String provider)` Returns a new instance of `SecureRandom` that utilizes the specified algorithm from the specified provider.
`Provider`	`getProvider()` Returns the provider associated with this `SecureRandom`.
`static byte[]`	`getSeed(int numBytes)` Generates and returns the specified number of seed bytes, computed using the seed generation algorithm used by this `SecureRandom`.
`protected int`	`next(int numBits)` Generates and returns an `int` containing the specified number of random bits (right justified, with leading zeros).
`void`	`nextBytes(byte[] bytes)` Generates and stores random bytes in the given `byte[]` for each array element.
`void`	`setSeed(byte[] seed)` Seeds this `SecureRandom` instance with the specified `seed`.
`void`	`setSeed(long seed)` Seeds this `SecureRandom` instance with the specified eight-byte `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

- Constructor Detail
  - SecureRandom
```
public SecureRandom()
```
    Constructs a new SecureRandom that uses the default algorithm.
  - SecureRandom
```
public SecureRandom(byte[] seed)
```
    Constructs a new seeded SecureRandom that uses the default algorithm. Seeding SecureRandom may be insecure.
  - SecureRandom
```
protected SecureRandom(SecureRandomSpi secureRandomSpi,
            Provider provider)
```
    Constructs a new instance of SecureRandom using the given implementation from the specified provider.
    
    Parameters:
    secureRandomSpi - the implementation.
    provider - the security provider.
- Method Detail
  - getInstance
```
public static SecureRandom getInstance(String algorithm)
                                throws NoSuchAlgorithmException
```
    Returns a new instance of SecureRandom that utilizes the specified algorithm.
    
    Parameters:
    algorithm - the name of the algorithm to use.
    
    Returns:
    a new instance of SecureRandom that utilizes the specified algorithm.
    
    Throws:
    
    NoSuchAlgorithmException - if the specified algorithm is not available.
    
    NullPointerException - if algorithm is null.
  - getInstance
```
public static SecureRandom getInstance(String algorithm,
                       String provider)
                                throws NoSuchAlgorithmException,
                                       NoSuchProviderException
```
    Returns a new instance of SecureRandom that utilizes the specified algorithm from the specified provider.
    
    Parameters:
    algorithm - the name of the algorithm to use.
    provider - the name of the provider.
    
    Returns:
    a new instance of SecureRandom that utilizes the specified algorithm from the specified provider.
    
    Throws:
    
    NoSuchAlgorithmException - if the specified algorithm is not available.
    
    NoSuchProviderException - if the specified provider is not available.
    
    NullPointerException - if algorithm is null.
    
    IllegalArgumentException - if provider == null || provider.isEmpty()
  - getInstance
```
public static SecureRandom getInstance(String algorithm,
                       Provider provider)
                                throws NoSuchAlgorithmException
```
    Returns a new instance of SecureRandom that utilizes the specified algorithm from the specified provider.
    
    Parameters:
    algorithm - the name of the algorithm to use.
    provider - the security provider.
    
    Returns:
    a new instance of SecureRandom that utilizes the specified algorithm from the specified provider.
    
    Throws:
    
    NoSuchAlgorithmException - if the specified algorithm is not available.
    
    NullPointerException - if algorithm is null.
    
    IllegalArgumentException - if provider == null
  - getProvider
```
public final Provider getProvider()
```
    Returns the provider associated with this SecureRandom.
    
    Returns:
    the provider associated with this SecureRandom.
  - getAlgorithm
```
public String getAlgorithm()
```
    Returns the name of the algorithm of this SecureRandom.
    
    Returns:
    the name of the algorithm of this SecureRandom.
  - setSeed
```
public void setSeed(byte[] seed)
```
    Seeds this SecureRandom instance with the specified seed. Seeding SecureRandom may be insecure.
  - setSeed
```
public void setSeed(long seed)
```
    Seeds this SecureRandom instance with the specified eight-byte seed. Seeding SecureRandom may be insecure.
    
    Overrides:
    
    setSeed in class Random
  - nextBytes
```
public void nextBytes(byte[] bytes)
```
    Generates and stores random bytes in the given byte[] for each array element.
    
    Overrides:
    
    nextBytes in class Random
    
    Parameters:
    bytes - the byte[] to be filled with random bytes.
  - next
```
protected final int next(int numBits)
```
    Generates and returns an int containing the specified number of random bits (right justified, with leading zeros).
    
    Overrides:
    
    next in class Random
    
    Parameters:
    numBits - number of bits to be generated. An input value should be in the range [0, 32].
    
    Returns:
    an int containing the specified number of random bits.
  - getSeed
```
public static byte[] getSeed(int numBytes)
```
    Generates and returns the specified number of seed bytes, computed using the seed generation algorithm used by this SecureRandom.
    
    Parameters:
    numBytes - the number of seed bytes.
    
    Returns:
    the seed bytes
  - generateSeed
```
public byte[] generateSeed(int numBytes)
```
    Generates and returns the specified number of seed bytes, computed using the seed generation algorithm used by this SecureRandom.
    
    Parameters:
    numBytes - the number of seed bytes.
    
    Returns:
    the seed bytes.

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IT. Expert System.

Android Reference

SecureRandom

Class SecureRandom

Supported Algorithms

Seeding SecureRandom may be insecure

Constructor Summary

Method Summary

Methods inherited from class java.util.Random

Methods inherited from class java.lang.Object

Constructor Detail

SecureRandom

SecureRandom

SecureRandom

Method Detail

getInstance

getInstance

getInstance

getProvider

getAlgorithm

setSeed

setSeed

nextBytes

next

getSeed

generateSeed

Android Reference

Java basics

Java Enterprise Edition (EE)

Java Standard Edition (SE)

SQL

HTML

PHP

CSS

Java Script

MYSQL

JQUERY

VBS

REGEX

C

C++

C#

Design patterns

RFC (standard status)

RFC (proposed standard status)

RFC (draft standard status)

RFC (informational status)

RFC (experimental status)

RFC (best current practice status)

RFC (historic status)

RFC (unknown status)

IT dictionary

Seeding `SecureRandom` may be insecure