# US 12,120,096 B2 · Private 5G cellular connectivity as a service through full-stack wireless steganography

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- Number: US 12,120,096 B2
- Document ID: US12120096B2
- Status: Granted
- Kind: B2
- Application number: 17/316,773
- Filed: 2021-05-11
- Published: 2021-11-11
- Granted: 2024-10-15
- Earliest claimed: 2020-05-11
- Assignees: Northeastern University
- Applicants: Northeastern University
- Inventors: Tommaso Melodia; Leonardo Bonati; Salvatore D'Oro; Francesco Restuccia
- Web page: https://patentgrep.com/patent/US12120096B2

## CPC

- H04L 27/0008: {arrangements for allowing a transmitter or receiver to use more than one type of modulation (negotiating modulation type for two-way transmission paths H04L5/1453)}
- H04L 63/0428: {wherein the data content is protected, e.g. by encrypting or encapsulating the payload}
- G06F 21/556: {involving covert channels, i.e. data leakage between processes (inhibiting the analysis of circuitry or operation with measures against power attack G06F21/755)}
- G06F 21/606: {by securing the transmission between two devices or processes}
- H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)}
- H04L 5/0055: {Physical resource allocation for ACK/NACK (for physical mapping arrangements in ARQ protocols H04L1/1861)}
- H04L 27/0012: {arrangements for identifying the type of modulation}
- H04L 27/3461: {in order to transmit a subchannel}
- H04L 63/1475: {Passive attacks, e.g. eavesdropping or listening without modification of the traffic monitored}
- H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT}
- H04L 5/14: Two-way operation using the same type of signal, i.e. duplex
- H04L 27/02: Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation (H04L27/32 takes precedence)
- H04L 27/10: Frequency-modulated carrier systems, i.e. using frequency-shift keying (H04L27/32 takes precedence)
- H04L 27/18: Phase-modulated carrier systems, i.e. using phase-shift keying (H04L27/32 takes precedence)
- H04L 27/2602: {Signal structure}
- H04L 27/34: Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L 27/3488: {Multiresolution systems}
- H04L 63/0869: {for achieving mutual authentication (cryptographic mechanisms or cryptographic arrangements for mutual authentication H04L9/3273)}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A steganographic communication system and method are provided. A covert packet generator can embed a stream of covert data as covert data symbols within primary I/Q symbols of a primary data stream in a covert packet. The covert packet has a data structure having a header, a payload, and a payload error detecting code. The header includes information on how to demodulate the covert packet by a receiver. The covert packet generator can also determine if a number of primary I/Q symbols is large enough to generate the header and can generate displacements in the primary I/Q symbols in a constellation diagram randomly in a plurality of transmissions to mimic channel noise. A transmitter and receiver can provide mutual authentication for covert transmissions.

## Claims

### Claim 1

A device for steganographic communication comprising:
a transmitter including one or more processors and memory, instructions stored in the memory, the transmitter comprising a covert packet generator operative to receive a covert data stream of covert data and a primary data stream of primary in-phase and quadrature (I/Q) symbols, and to embed the covert data as covert data symbols within the primary I/Q symbols in a covert packet, wherein the covert packet has a data structure comprising a header, a payload, and a payload error detecting code; and
a radio frequency (RF) front end and antenna operative to transmit and receive radio frequency signals, the RF front end in communication with the covert packet generator to receive the covert packet for transmission,
wherein the covert packet generator is operative to determine if a number of the primary I/Q symbols is large enough to generate the header of the covert packet.

### Claim 2 (depends on 1)

The device of claim 1, wherein the header includes:
a payload length field containing a total length of the covert payload and the payload error detecting code;
an information field containing information on how to demodulate the covert packet by a receiver; and
a header error detecting code field.

### Claim 3 (depends on 2)

The device of claim 2, wherein the information field contains:
a packet number comprising a sequential number to identify the covert packet;
covert modulation parameters indicative of a modulation scheme, the cover modulation parameters including a modulation order, coding map associating covert bit sequences to modulated covert symbols, and a packet type; and
a threshold flag indicative of a distance between the covert data symbols on a constellation diagram.

### Claim 4 (depends on 2)

The device of claim 2, wherein the information field contains an identification of a packet type, wherein the packet type is one or more of an acknowledgement (ACK) message type, a negative-acknowledgement (NACK) message type, a covert data-carrying type, a packet information-carrying type, a challenge message type, a challenge response message type, and an authentication acknowledgement message type.

### Claim 5 (depends on 4)

The device of claim 4, wherein the packet information-carrying type includes information on source and destination of covert packets and a total number of covert packets in a transmission.

### Claim 6 (depends on 1)

The device of claim 1, wherein the covert packet generator is operative to generate displacements in the primary I/Q symbols in a constellation diagram based on the covert data symbols.

### Claim 7 (depends on 6)

The device of claim 6, wherein the covert packet generator is operative to generate the displacements randomly among a plurality of transmitted covert packets in a transmission stream and to include a threshold flag in the header of the covert packet comprising a value indicative of the displacement in the I/Q symbols, wherein the value is changed on a per-packet basis.

### Claim 8 (depends on 1)

The device of claim 1, wherein the transmitter is further operative to:
transmit a queue of covert packets to a receiver, located remotely from the transmitter, and to wait a determined time for an acknowledgement message or a negative-acknowledgement message from the receiver;
retransmit the queue of covert packets to the receiver upon receipt of a negative-acknowledgement message;
retransmit the queue of covert packets to the receiver upon expiration of the determined time if no acknowledgement message or negative-acknowledgement message has been received at the transmitter; or
stop attempted transmissions of the queue of covert packets after a number of retransmission attempts exceeds a determined threshold.

### Claim 9 (depends on 1)

A system for steganographic communication comprising:
the device of claim 1; and
a receiver located remotely from the transmitter, the receiver including one or more processors and memory, instructions stored in the memory, the receiver comprising:
a covert packet detector operative to receive incoming transmissions from the transmitter, to detect a presence of the covert packet, and to extract covert information from the covert packet; and
a covert demodulator operative to demodulate the covert symbols.

### Claim 10 (depends on 9)

The system of claim 9, wherein the transmitter and the receiver are operative to send covert authentication messages for mutual authentication, the covert authentication messages including a type indicator including a challenge type, a challenge response, and an authentication acknowledgement type.

### Claim 11 (depends on 10)

The system of claim 10, wherein:
the transmitter is operative to authenticate the receiver by:
sending a covert authentication message to the receiver including an authentication code,
receiving a reply covert message from the receiver including an authentication code result,
determining if the authentication code result from the receiver matches an expected authentication code result, and
if the authentication code result matches the expected authentication code result, sending a covert authentication acknowledgement message to the receiver; and
the receiver is operative to authenticate the transmitter by:
sending a further covert authentication message to the transmitter including a further authentication code,
receiving a further reply covert message from the transmitter including a further authentication code result,
determining if the further authentication code result from the transmitter matches a further expected authentication code result, and
if the further authentication code result matches the further expected authentication code result, sending a further covert authentication acknowledgement message to the transmitter.

### Claim 12

A method of steganographic communication, comprising:
at a transmitter, generating a covert packet containing covert data embedded as covert symbols within primary in-phase and quadrature (I/Q) symbols, the covert packet having a data structure comprising a header, a payload, and a payload error detecting code;
determining if a number of the primary I/Q symbols is large enough to generate the header of the covert packet; and
transmitting the covert packet as a radio frequency (RF) transmission to a receiver located remotely from the transmitter.

### Claim 13 (depends on 12)

The method of claim 12, further comprising generating the header to include:
a payload length field containing a total length of the covert payload and the payload error detecting code;
an information field containing information on how to demodulate the covert packet by a receiver, wherein the information field contains:
a packet number comprising a sequential number to identify the covert packet,
covert modulation parameters, the cover modulation parameters including a modulation order, coding map associating covert bit sequences to modulated covert symbols, and a packet type, and
a threshold flag indicative of a distance between the covert data symbols on a constellation diagram; and
a header error detecting code field.

### Claim 14 (depends on 12)

The method of claim 12, further comprising generating displacements in the primary I/Q symbols in a constellation diagram based on the covert data symbols.

### Claim 15 (depends on 14)

The method of claim 14, further comprising:
generating the displacements randomly among a plurality of transmitted covert packets in a transmission stream;
generating a threshold flag in the header of the covert packet comprising a value indicative of the displacement in the I/Q symbols; and
changing the value on a per-packet basis.

### Claim 16 (depends on 12)

The method of claim 12, further comprising:
transmitting the acknowledgement message and the negative-acknowledgement message as covert packets by the receiver;
retransmitting the queue of covert packets to the receiver upon receipt of a negative-acknowledgement message;
retransmitting the queue of covert packets to the receiver upon expiration of the determined time if no acknowledgement message or negative-acknowledgement message has been received at the transmitter; or
stopping attempted transmissions of the queue of covert packets after a number of retransmission attempts exceeds a determined threshold.

### Claim 17 (depends on 16)

The method of claim 16, further comprising, at the transmitter and/or the receiver, sending covert authentication messages for mutual authentication, the covert authentication messages including a type indicator including a challenge type, a challenge response type, and an authentication acknowledgement type.

### Claim 18 (depends on 12)

The method of claim 12, further comprising, at the receiver located remotely from a transmitter:
receiving incoming transmissions from the transmitter;
detecting a presence of the covert packet by reading a length of a covert payload and a payload error code, a packet number, and modulation parameters in the header;
extracting covert information from the covert packet; and
demodulating the covert symbols.