1. LACK - a VoIP steganographic method
Wojciech Mazurczyk, Jozef Lubacz
(2010). Telecommun Syst , 45,
DOI: /s y
4.5 to 7.5 minutes
9/13/2018
ZHAO PING

2. Summary Procedure Insertion Rate (IR) A new method
modification of both packets and time dependence
Procedure
select packet => replace payload => send after certain delay
Insertion Rate (IR)
Decrease during a call duration
Acceptable packet loss rate IR
Make it consistent with the real call duration probability distribution, which makes it difficult to be detected.
Make the quality acceptable by the a proper QoS in terms of loss rate.

3. Comments - appreciative
Clear threat model
Statistical analysis of lost packets
Statistical analysis on VoIP calls duration
Active warden
All covered in the design of IR.
Active warden
Drop both hidden packet and normal packet, which will affect call quality

4. Comments - critical Low academic quality
Term inconsistent, causing confusion
Call duration probability distribution
call duration distribution
probability distribution
call distribution
Expression vague
“To limit the risk of detection of the hidden data, the delay chosen by LACK users should be as low as possible.”

5. Comments - critical Conclusion biased
Lack: Modifying packets & time relationship
Modification of packets (IR)
Analysis of call duration distribution
Analysis of the influence on call quality
Formulas
Modification of time relationship
Longer than de-jitter buffer
as low as possible
Throughput
Jitter, delay, loss
3. more than de-jitter buffer (30~70 ms)

6. Question
LACK has proved itself to be acceptable and reliable on hidden data insertion rate. However, is this enough for LACK to be applied in VOIP?