In one embodiment, method of increasing security of computing-device mobile device communications comprising executing on one or more processors in a central repository server the step of obtaining a first user's public key. The first user's public key is one of a pair of certification keys generated by an application in a first user's computing device. The method includes the step of obtaining, from the first user via the first user's computing device, a set of first user's communication identifiers. The set of first user's communication identifier includes a first user's mobile device number, a first user's email address, or a first user's online social network identifier. The method includes the step of receiving a set of first user's communication identifiers from the first user via the first user's computing device. The method includes the step of generating one or more associations of the first user's public key with the set of first user's communication identifiers. With the one or more processors in the central repository server implementing delivery of the first user's public key to a second user's mobile device the method receives from another application operating in the second user's mobile device, a request for the first user's public key. The request includes at least one of the first user's communication identifiers. The method includes the step of retrieving the first user's public key, the set of first user's communication identifiers, and the association of the first user's public key with the set of first user's communication identifiers from the computer data store. The method includes the step of authenticating that the at least one of the first user's communication identifiers received from the other application is associated with the first user's public key using the retrieved associations of the first user's public key with the set of first user's communication identifiers from the computer data store. The method includes the step of communicating the first user's public key to the other application operating in the second user's mobile device.