Full frame encryption and modulation obfuscation using channel-independent preamble identifier

Hanif Rahbari, Marwan Krunz

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


The broadcast nature of wireless communications exposes various transmission attributes, such as the packet size, inter-packet times, and the modulation scheme. These attributes can be exploited by an adversary to launch passive (e.g., traffic analysis) or selective jamming attacks. This security problem is present even when frame headers and payloads can be encrypted. For example, by determining the modulation scheme, the attacker can estimate the data rate, and hence the payload size. In this paper, we propose Friendly CryptoJam (FCJ), a scheme that decorrelates the payload's modulation scheme from other transmission attributes by embedding information symbols into the constellation map of the highest-order modulation scheme supported by the system (a concept we refer to as indistinguishable modulation unification). Such unification is done using the least-complex trellis-coded modulation schemes, which are combined with a secret pseudo-random sequence in FCJ to conceal the rate-dependent pattern imposed by the code. It also preserves the bit error rate performance of the payload's original modulation scheme. At the same time, modulated symbols are encrypted to hide PHY-/MAC layer fields. To identify the Tx and synchronously generate the secret sequence at the Tx and Rx, an efficient identifier embedding technique based on Barker sequences is proposed, which exploits the structure of the preamble and overlays a frame-specific identifier on it. We study the implications of the scheme on PHY-layer functions through simulations and testbed experiments. Our results confirm the efficiency of FCJ in hiding the targeted attributes.

Original languageEnglish (US)
Article number7495006
Pages (from-to)2732-2747
Number of pages16
JournalIEEE Transactions on Information Forensics and Security
Issue number12
StatePublished - Dec 2016


  • PHY-layer security
  • Universal Software Radio Peripheral (USRP)
  • modulation unification
  • preamble
  • side-channel information
  • untraceable TCM

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality
  • Computer Networks and Communications


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