A Survey of Key Technologies for Constructing Network Covert Channel

Table 1

The abbreviations used in our article.

Abbreviation	Full name
SSL	Secure sockets layer
Tor	The second-generation onion router
DPI	Deep packet inspection
I2P	Invisible internet project
ML	Machine learning
DL	Deep learning
CTCs	Covert timing channels
CSCs	Covert storage channels
URL	Uniform resource locator
E2M	End-to-middle
C&C	Command and control
IPDs	Internet packet delays
BER	Bit error rate
PDU	Protocol data unit
ICMP	Internet control message protocol
ECDH	Elliptic curve Diffie-Hellman
TCP ISNs	TCP initial sequence numbers
PPTP	Point-to-point tunneling protocol
L2TP	Layer two-tunneling protocol
VTP	VLAN trunking protocol
IPSec	IP security
DHT	Distributed hash table
ESP	Encapsulating security payload
SDN	Software defined network
IoT	Internet of things
ICS	Industrial control systems
DGA	Domain generation algorithm