http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.crypto.tls;

class DTLSEpoch
{
    private final DTLSReplayWindow replayWindow = new DTLSReplayWindow();

    private final int epoch;
    private final TlsCipher cipher;

    private long sequenceNumber = 0;

    DTLSEpoch(int epoch, TlsCipher cipher)
    {
        if (epoch < 0)
        {
            throw new IllegalArgumentException("'epoch' must be >= 0");
        }
        if (cipher == null)
        {
            throw new IllegalArgumentException("'cipher' cannot be null");
        }

        this.epoch = epoch;
        this.cipher = cipher;
    }

    long allocateSequenceNumber()
    {
        // TODO Check for overflow
        return sequenceNumber++;
    }

    TlsCipher getCipher()
    {
        return cipher;
    }

    int getEpoch()
    {
        return epoch;
    }

    DTLSReplayWindow getReplayWindow()
    {
        return replayWindow;
    }

    long getSequenceNumber()
    {
        return sequenceNumber;
    }
}