A Survey of Key Technologies for Constructing Network Covert Channel

Table 3

E2M proxy.

E2M	Tag composition	Tag location	Blocking strategy	Deployment requirement
Telex [22]	(i) An ECDH public key point.; (ii) A hash of the ECDH secret shared with ISP.	TLS client nonce	Only tagged flow	Inline-blocking and redirecting components provided by ISP.
Cirripede [64]	(i) An ECDH public key point.; (ii) A hash of the ECDH secret shared with ISP.	TCP ISNs	All connections	Inline-blocking and redirecting components provided by ISP.
Decoy routing [63]	(i) An HMAC of the previously established shared secret key.; (ii) The current hour.; (iii) A per-hour sequence number.	TLS client nonce	Only the tagged flow	Inline-blocking and redirecting components provided by ISP.
Tapdance [20]	The client’s connection-specific elliptic curve public key point.	TLS ciphertext	Not blocking	(i) A passive tap that observes traffic transiting the ISP.; (ii) The ability to inject new packets.