Methods for providing communication security between computerized devices in, for example, an ad hoc or temporary networked environment. In one embodiment, the network comprises an untrusted network, and the method includes providing network security apparatus adapted to create security associations between devices on the network, including mutual authentication. The method further may comprise encrypting traffic between the associated devices for e.g., data confidentiality and integrity protection by running one or more computer programs on the respective devices. In one variant, the network security apparatus comprises a software entity disposed at least partly within the software stack of the devices. The associated devices may be for example fixed or portable, and may be untrusted (e.g., have an untrusted operating systems).