Computer Security and Cryptography

16.2 U.S. PATENT ’770 [HELLMAN ET AL., 1980; DIFFIE AND HELLMAN, 1976]

The Diffie–Hellman key-exchange scheme uses these rules:

DH1.	User_ID[i] with identifier ID[i] chooses a secret key ki and computes xi = qki (modulo p). Table 16.1, containing the pairs (ID[i],xi), is maintained by the system administrator.
DH2.	When User_ID[i] and User_ID[j] wish to communicate they construct a common (User_ID[i]-User_ID[j]) key as follows: – User_ID[i] reads xj from the table and computes (modulo p). – User_ID[j] reads xi from the table and computes (modulo p).   The common (User_ID[i]-User-ID[j]) key is xi,j = xj,i.