Abstract: During operation, an electronic device may receive, from a second electronic device, information that specifies or that corresponds to one or more distortions, where the one or more distortions are associated with measurements of a physical parameter that are performed by a sensor in the second electronic device. Then, the electronic device may determine, based at least in part on the information, the one or more distortions. Moreover, the electronic device may compare the determined one or more distortions with historical values of the one or more distortions. Note that the historical values of the one or more distortions may be specified by or may correspond to historical information that is received from one or more third electronic devices. Next, based at least in part on the comparison, the electronic device may selectively authenticate an individual associated with the second electronic device.

Abstract: During operation, an electronic device may receive, from a second electronic device, information that specifies or that corresponds to one or more distortions, where the one or more distortions are associated with measurements of a physical parameter that are performed by a sensor in the second electronic device. Then, the electronic device may determine, based at least in part on the information, the one or more distortions. Moreover, the electronic device may compare the determined one or more distortions with historical values of the one or more distortions. Note that the historical values of the one or more distortions may be specified by or may correspond to historical information that is received from one or more third electronic devices. Next, based at least in part on the comparison, the electronic device may selectively authenticate an individual associated with the second electronic device.

Abstract: An electronic device that accesses content is described. During operation, the electronic device may obtain a secure message and information specifying a second electronic device. Then, the electronic device may contact, based at least in part on the information, the second electronic device, where the contact occurs via a separate second communication channel that is different from a communication channel used to obtain the secure message and the information. Moreover, the electronic device may receive, from the second electronic device, second information, where the second information facilitates access to the content associated with the secure message. Next, the electronic device may access the content in the secure message based at least in part on the second information.

Abstract: During operation, a digital asset (such as a digital file or a token) on an electronic device receives, from the electronic device, a vector of challenges, where the vector of challenges includes N challenges and N is a non-zero integer. Then, the digital asset selects a subset of the vector of challenges. Moreover, the digital asset compares the subset of the vector of challenges with a stored second subset of a second vector of challenges. When the subset of the vector challenges matches the stored second subset of the second vector of challenges: the digital asset deems the electronic device authenticated; the digital asset provides, to the electronic device, a third vector of challenges, where the third vector of challenges includes M challenges and M is a non-zero integer; and the electronic device selects and stores a third subset of the third vector of challenges.

Abstract: During operation, an electronic device may receive, from a second electronic device, information that specifies or that corresponds to one or more distortions, where the one or more distortions are associated with measurements of a physical parameter that are performed by a sensor in the second electronic device. Then, the electronic device may determine, based at least in part on the information, the one or more distortions. Moreover, the electronic device may compare the determined one or more distortions with historical values of the one or more distortions. Note that the historical values of the one or more distortions may be specified by or may correspond to historical information that is received from one or more third electronic devices. Next, based at least in part on the comparison, the electronic device may selectively authenticate an individual associated with the second electronic device.