When software generates predictable values in a context requiring unpredictability, it may be possible for an attacker to guess the next value that will be generated, and use this guess to impersonate another user or access sensitive information.
As the java.util.Random
class relies on a pseudorandom number generator, this class and relating java.lang.Math.random()
method should not be used for security-critical applications or for protecting sensitive data. In such context, the
java.security.SecureRandom
class which relies on a cryptographically strong random number generator (RNG) should be used in place.
Random random = new Random(); byte bytes[] = new byte[20]; random.nextBytes(bytes);
SecureRandom random = new SecureRandom(); byte bytes[] = new byte[20]; random.nextBytes(bytes);