Hiding Information in Short Network Packets

Lossless compression of payload in network packets and using the freed space for transfer of secret messages has been known for long. However, for short payloads, usual lossless compressors do not achieve any compression. We address this case by proposing both a Huffman-inspired and a runlength-inspired coding of payload when byte values are not equi-distributed. We provide numeric results for different payload lengths and byte value distributions and achieve compression ratios of 70% in the best case, leaving 30% of the message space for the secret message. We also investigate possibilities for the detection of such an embedding via changes in entropy.