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## javacard.security
Class RandomData

    java.lang.Object
      javacard.security.RandomData

    @TransactionType(value=SUPPORTS)
    public abstract class RandomData

extends Object

The `RandomData` abstract class is the base class for random number generation. Implementations of `RandomData` algorithms must extend this class and implement all the abstract methods.

Since:
  Java Card 2.x, Java Card 3.0

Field Summary
`static byte` | `ALG_PSEUDO_RANDOM` Utility pseudo-random number generation algorithms.
`static byte` | `ALG_SECURE_RANDOM` Cryptographically secure random number generation algorithms.
`static String` | `SERVICE_NAME` This cryptographic service name, as used to lookup implemented algorithms.

Constructor Summary
`protected` | `RandomData()` Protected constructor for subclassing.

Method Summary
`abstract void` | `generateData(byte[] buffer, short offset, short length)` Generates random data.
`static RandomData` | `getInstance(byte algorithm)` Creates a `RandomData` instance of the selected algorithm.
`static RandomData` | `getInstance(String algorithm)` Creates a `RandomData` instance of the selected algorithm.
`static RandomData` | `getInstance(String algorithm, String provider)` Creates a `RandomData` instance of the selected algorithm.
`abstract void` | `setSeed(byte[] buffer, short offset, short length)` Seeds the random data generator.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### SERVICE_NAME

    public static final String SERVICE_NAME

  This cryptographic service name, as used to lookup implemented algorithms.

  Since:
    Java Card 3.0
  See Also:
    Constant Field Values

### ALG_PSEUDO_RANDOM

    public static final byte ALG_PSEUDO_RANDOM

  Utility pseudo-random number generation algorithms. The random number sequence generated by this algorithm need not be the same even if seeded with the same seed data.

  Even if a transaction is in progress, the update of the internal state shall not participate in the transaction.

  The `String` name equivalent to this algorithm type to use as parameter to the `getInstance(String algorithm, ...)` method is `"PSEUDO_RANDOM"`

  See Also:
    Constant Field Values

### ALG_SECURE_RANDOM

    public static final byte ALG_SECURE_RANDOM

  Cryptographically secure random number generation algorithms.

  The `String` name equivalent to this algorithm type to use as parameter to the `getInstance(String algorithm, ...)` method is `"SECURE_RANDOM"`

  See Also:
    Constant Field Values

Constructor Detail

### RandomData

    protected RandomData()

  Protected constructor for subclassing.

Method Detail

### getInstance

    public static final RandomData getInstance(byte algorithm)
                                        throws CryptoException

  Creates a `RandomData` instance of the selected algorithm. The pseudo random `RandomData` instance's seed is initialized to a internal default value.

  This method returns an instance of the specified algorithm supported by the most preferred provider of this cryptographic service. Note that the list of installed providers may be retrieved via the `CryptoServices.getProviders()` method.

  A call to this method is equivalent to a call to `getInstance(java.lang.String)` with the `algorithm` parameter set to the equivalent `String` algorithm name - as listed in the `ALG_*` constants above.

  Parameters:
    `algorithm` - the desired random number algorithm. Valid codes listed in `ALG_*` constants above. See `ALG_PSEUDO_RANDOM`.
  Returns:
    the `RandomData` object instance of the requested algorithm
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.NO_SUCH_ALGORITHM` if the requested algorithm is not supported.
    `SecurityException` - if creating an instance of this cryptographic service is not granted.

### getInstance

    public static final RandomData getInstance(String algorithm)
                                        throws CryptoException

  Creates a `RandomData` instance of the selected algorithm. The pseudo random `RandomData` instance's seed is initialized to a internal default value.

  This method returns an instance of the specified algorithm supported by the most preferred provider of this cryptographic service. Note that the list of installed providers may be retrieved via the `CryptoServices.getProviders()` method.

  Parameters:
    `algorithm` - the desired random number algorithm name. Valid names listed in `ALG_*` constants above. See `ALG_PSEUDO_RANDOM`.
  Returns:
    the `RandomData` object instance of the requested algorithm
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.NO_SUCH_ALGORITHM` if the requested algorithm is not supported.
    `NullPointerException` - if `algorithm` is null.
    `SecurityException` - if creating an instance of this cryptographic service is not granted.
  Since:
    Java Card 3.0

### getInstance

    public static final RandomData getInstance(String algorithm,
                                               String provider)
                                        throws CryptoException

  Creates a `RandomData` instance of the selected algorithm. The pseudo random `RandomData` instance's seed is initialized to a internal default value.

  Parameters:
    `algorithm` - the desired random number algorithm name. Valid names listed in `ALG_*` constants above. See `ALG_PSEUDO_RANDOM`.
    `provider` - the desired key agreement algorithm provider.
  Returns:
    the `RandomData` object instance of the requested algorithm
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.NO_SUCH_ALGORITHM` if the requested algorithm is not supported.
    `NullPointerException` - if `algorithm` or `provider` is null.
    `SecurityException` - if creating an instance of this cryptographic service is not granted.
  Since:
    Java Card 3.0

### generateData

    public abstract void generateData(byte[] buffer,
                                      short offset,
                                      short length)
                               throws CryptoException

  Generates random data.

  Parameters:
    `buffer` - the output buffer
    `offset` - the offset into the output buffer
    `length` - the length of random data to generate
  Throws:
    `CryptoException` - with the following reason codes:
    - `CryptoException.ILLEGAL_VALUE` if the `length` parameter is zero.

### setSeed

    public abstract void setSeed(byte[] buffer,
                                 short offset,
                                 short length)

  Seeds the random data generator.

  Parameters:
    `buffer` - the input buffer
    `offset` - the offset into the input buffer
    `length` - the length of the seed data

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Copyright (c) 2009 Sun Microsystems, Inc. All rights reserved.