Package org.cryptomator.cryptolib.common

Class ReseedingSecureRandom

java.lang.Object

java.util.Random

java.security.SecureRandom

org.cryptomator.cryptolib.common.ReseedingSecureRandom

All Implemented Interfaces:

Serializable

public class ReseedingSecureRandom
extends SecureRandom

Wraps a fast CSPRNG, which gets reseeded automatically after a certain amount of bytes has been generated.

Java 8 Example:

  SecureRandom csprng = ReseedingSecureRandom.create(SecureRandom.getInstanceStrong());
 

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
ReseedingSecureRandom(SecureRandom seeder, SecureRandom csprng, long reseedAfter, int seedLength)

Method Summary

Modifier and Type	Method	Description
static ReseedingSecureRandom	create(SecureRandom seeder)	Creates a pre-configured automatically reseeding SHA1PRNG instance, reseeding itself with 440 bits from the given seeder after generating 2^30 bytes, thus satisfying recommendations by NIST SP 800-90A Rev 1.

Methods inherited from class java.security.SecureRandom

generateSeed, getAlgorithm, getInstance, getInstance, getInstance, getInstanceStrong, getProvider, getSeed, next, nextBytes, setSeed, setSeed

Methods inherited from class java.util.Random

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, 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

ReseedingSecureRandom

public ReseedingSecureRandom(SecureRandom seeder,
                             SecureRandom csprng,
                             long reseedAfter,
                             int seedLength)

Parameters:

seeder - RNG for high-quality random numbers. E.g. SecureRandom.getInstanceStrong() in Java 8+ environments.

csprng - A fast csprng implementation, such as SHA1PRNG, that will be wrapped by this instance.

reseedAfter - How many bytes can be read from the csprng, before a new seed will be generated.

seedLength - Number of bytes generated by seeder in order to seed csprng.

Method Detail

create

public static ReseedingSecureRandom create(SecureRandom seeder)

Creates a pre-configured automatically reseeding SHA1PRNG instance, reseeding itself with 440 bits from the given seeder after generating 2^30 bytes, thus satisfying recommendations by NIST SP 800-90A Rev 1.

Parameters:

seeder - RNG for high-quality random numbers. E.g. SecureRandom.getInstanceStrong() in Java 8+ environments.

Returns:

An automatically reseeding SHA1PRNG suitable as CSPRNG for most applications.