Embodiments include a method for secure data storage including constructing an encryption key from a plurality of key elements, the constructing including distributing the plurality of key elements to a plurality of key maintenance entities, each of the plurality of key maintenance entities employing a plurality of independent safe guards for their respective key elements of the plurality of key elements; and requiring access to the plurality of key elements to construct the encryption key. The method includes receiving a subset of the plurality of key elements via a twice-encrypted communications channel; and regenerating the encryption key at the client node; and after encrypting data, deleting the subset of the plurality of key elements received over the twice-encrypted communications channel, retaining any of the plurality of key elements previously stored at the client node.

A processor coupled to a first communication device produces and transmits a first encoded vector and a second encoded vector to a second communication device via a communication channel that applies a channel transformation to the encoded vectors during transmission. A processor coupled to the second communication device receives the transformed signals, constructs a matrix based on the transformed signals, detects an effective channel thereof, and identifies left and right singular vectors of the effective channel. A precoding matrix is selected from a codebook of unitary matrices based on a message, and a second encoded vector is produced based on a second known vector, the precoding matrix, a complex conjugate of the left singular vectors, and the right singular vectors. A first symbol of the second encoded vector and a second symbol of the second encoded vector are sent to the first communication device for identification of the message.

Disclosed is a method of encrypting a data signal for providing to an input of a radio frequency transmitter, such as modulated baseband signals in the physical layer for wireless transmission. The method comprises receiving the data signal comprising one or more first frequency components with a first phase profile in a frequency band of interest; applying a dispersive encrypting signal filter to the data signal to generate an encrypted data signal comprising the one or more frequency components with a second phase profile, wherein the second phase profile is different to the first phase profile. Decryption is achieved by applying a decrypting filter to the encrypted data signal to substantially reverse the effect of the encrypting filter and recover the first phase profile.

A processor coupled to a first communication device produces and transmits a first encoded vector and a second encoded vector to a second communication device via a communication channel that applies a channel transformation to the encoded vectors during transmission. A processor coupled to the second communication device receives the transformed signals, constructs a matrix based on the transformed signals, detects an effective channel thereof, and identifies left and right singular vectors of the effective channel. A precoding matrix is selected from a codebook of unitary matrices based on a message, and a second encoded vector is produced based on a second known vector, the precoding matrix, a complex conjugate of the left singular vectors, and the right singular vectors. A first symbol of the second encoded vector and a second symbol of the second encoded vector are sent to the first communication device for identification of the message.

A processor coupled to a first communication device produces and transmits a first encoded vector and a second encoded vector to a second communication device via a communication channel that applies a channel transformation to the encoded vectors during transmission. A processor coupled to the second communication device receives the transformed signals, constructs a matrix based on the transformed signals, detects an effective channel thereof, and identifies left and right singular vectors of the effective channel. A precoding matrix is selected from a codebook of unitary matrices based on a message, and a second encoded vector is produced based on a second known vector, the precoding matrix, a complex conjugate of the left singular vectors, and the right singular vectors. A first symbol of the second encoded vector and a second symbol of the second encoded vector are sent to the first communication device for identification of the message.

A wireless communication device configures a first spatial subchannel in a shared frequency channel for communication with a first node in a first wireless network, and a second spatial subchannel in the shared frequency channel for communication with a second node in a second wireless network, the second wireless network different than the first wireless network. The wireless communication device employs the first spatial subchannel and the second spatial subchannel for communicating concurrently in the first wireless network and the second wireless network.

Disclosed is a blind authentication method for a frequency selective fading channel based on a smoothing technique. The method includes: transmitting carrier signals to a frequency selective fading channel having multiple paths, where each carrier signal includes an authentication signal, a pilot signal and an information signal, receiving the carrier signals, performing BKIC processing on a carrier signal in each path to obtain a target signal, and performing differential signal processing on the target signal to obtain a target authentication signal, obtaining a reference signal based on a key and the pilot signal in the each path, performing the differential signal processing on the reference signal to obtain a reference authentication signal, and calculating a correlation between the target authentication signal and the reference authentication signal to obtain a test statistic; and comparing the test statistic with a prescribed threshold to determine whether the carrier signal in the each of the plurality of paths can pass authentication.

Provided is a physical layer blind authentication method for a time-varying fading channel based on belief propagation. The method includes that: a transmitter transmits a carrier signal to a wireless channel, the carrier signal includes an authentication signal, a pilot signal and an information signal, and the wireless channel is the time-varying fading channel; a receiver receives the carrier signal, and performs BKIC processing and differential signal processing on the carrier signal to obtain a target authentication signal, the receiver obtains a reference signal based on a key and the pilot signal, performs the differential signal processing on the reference signal to obtain a reference authentication signal, and calculates a correlation between the target authentication signal and the reference authentication signal to obtain a test statistic; and compares the test statistic with a prescribed threshold to determine whether the carrier signal is capable of passing authentication.

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a wireless device may receive a beamformed signal from a transmitting device. The wireless device may estimate a weighted sum based at least in part on one or more coefficients that relate to impairments associated with the transmitting device, a spatial location of the wireless device, and/or the like. The wireless device may determine a cryptographic key based at least in part on a ratio among the plurality of coefficients in the weighted sum, and one or more communications between the wireless device and the transmitting device may be secured based on the cryptographic key. Numerous other aspects are provided.

In a wireless communication system, a secure communication link is provided by producing a set of reference symbols selected from a modulation symbol constellation; generating a data-bearing pre-coding transform from information to be transmitted to a receiver; applying the data-bearing pre-coding transform to the set of reference symbols, thereby distorting the reference symbols with respect to the information, to produce a linear transformation signal; and transmitting the linear transformation signal to the receiver. The reference symbols are known at the receiver. The receiver removes the reference symbols from the linear transformation signal and decodes the data-bearing pre-coding transform.