Anonymous broadcast method, key exchange method, anonymous broadcast system, key exchange system, communication device, program

摘要

The present invention provides a technology of key exchange between N (≥2) persons, by which metadata relating to communication can be concealed. This anonymous broadcast method comprises: a first key generation step in which a communication device Ui generates a first key; a first anonymous broadcast step in which, regarding iϵ{1, …, n}, the communication device Ui designates a set R-{Ui}, and regarding iϵ{n+1, …, N}, the communication device Ui designates φ and anonymously broadcasts the first key; a second key generation step in which the communication device Ui generates a second key; a second anonymous broadcast step in which, regarding iϵ{1, …, n}, the communication device Ui designates the set R-{Ui}, and regarding iϵ{n+1, …, N}, the communication device Ui designates φ and anonymously broadcasts the second key; and a session key generation step in which regarding iϵ{1, …, n}, the communication device Ui generates a session key SK if a predetermined condition is satisfied.