Patent ID: 8429408

Claim:
A method of establishing a private key k A for use in a public key cryptographic system established between a first correspondent computing device and a second correspondent computing device, each of the first computing device and the second computing device comprising a cryptographic unit to perform cryptographic operations, the method comprising: a processor of the first correspondent computing device: a) establishing a private value x A from an output of a random number generator; b) computing a corresponding public key X A from the private value x A ; c) encrypting the public key X A using an encryption scheme and a first public key of a trusted party to establish an encrypted public key X A ′; d) forwarding the encrypted public key X A ′ to the trusted party; e) receiving from the trusted party encrypted private key reconstruction data and an implicit certificate, based upon the public key X A and a trusted party public key X CA ; f) applying a decryption key to recover the private key reconstruction data, the decryption key corresponding to a combination of the private value x A and a long-term public key Q CA of the trusted party; and, g) computing the private key k A from the private key reconstruction data, the private key k A being a discrete log private key corresponding to the long-term public key Q CA of the trusted party; whereby the first correspondent computing device may use the private key k A in a transfer of information including the implicit certificate with the second correspondent computing device, and whereby the second correspondent computing device may receive the implicit certificate and recover a first computing device public key Q A from the implicit certificate and the long-term public key Q CA .