Abstract: The present invention describes a method for enabling users of a cryptosystem to agree on secret keys. In one embodiment, a trusted agent chooses at least one individual key for each user, with at least a portion of such individual key being secret. At least some of the individual keys are then stored in physically secure devices, and the pair of users i and j use their individual keys to compute a common secret key. In another embodiment, each trustee of a group of trustees choose at least one individual key for each user, with at least some portion of such individual key being secret. The keys chosen by a sufficiently small number of such trustees, however, are insufficient for computing the common secret key of the users. Other hardware and software key exchange protocols based on these two techniques are also disclosed.