Patent ID: 7853015

Claim:
A method for generating a session key (sk) on demand in a network among n participating network devices (A, B, C, D) with up to t faulty devices, wherein t<n/2, the method comprising each participating network device (D): choosing a private and public key (d i , e i ) according to a public key encryption scheme, and broadcasting the public key (e i ) to each other participating network device (A, B, C); choosing a local contribution value (y i ) from a multiplicative group (G q ) of size q; in each case of receiving a public key (e j ) from one of the other participating network devices (A, B, C), encrypting the local contribution value (y i ) under the received public key (e j ) to an encrypted contribution value (y ij ) and sending in reply to the one of the other participating network devices (A, B, C) the encrypted contribution value (y ij ); receiving at least n−t−1 encrypted contribution values (y ji ) and deriving decrypted contribution values (y j ) by applying the private key (d i ); deriving a blinded session key (bsk i ) from the decrypted contribution values (y j ) and the local contribution value (y i ); agreeing on one of the blinded session keys (bsk j ) by using an agreement protocol; and deriving the session key (sk) from the agreed-on blinded session key (bsk j ) by applying one of the decrypted contribution values (y j ) and the contribution value (y i ).