auth - authentication using station-to-station protocol The following protocol, based on the Station-to-Station protocol, is used for mutual authentication of two parties, each possessing a certificate from the same certifying authority (CA).

In the description below: .TF CERTx

alpha is a Diffie-Hellman base used system wide

p is a Diffie-Hellman modulus used system wide

Rx is a random number of the same order as p .

PK x the public key of x

SK x the private key of x

CERT x the public key of x signed by the certifying authority

sig n ( x ) represents x signed with n 's private key

In the following, the parties are labelled 0 and 1.

Each sends its public key and certificate to the other together with a computation "alpha**r0 mod p" ( "alpha**r1 mod p" ) based on the Diffie-Hellman parameters contained in the certificate:

.EX 0 → 1 alpha**r0 mod p, CERTu0, PKu0 1 → 0 alpha**r1 mod p, CERTu1, PKu1

Each can now use the CA's public key and the certificate received to check that each has the other's public key.

Finally, each user signs values known to both that each can then verify:

.EX 0 → 1 sig0(alpha**r0 mod p, alpha**r1 mod p) 1 → 0 sig1(alpha**r0 mod p, alpha**r1 mod p)

At this point 0 and 1 can calculate the shared secret "alpha**(r0*r1)" , and can use it to encrypt later communications.

keyring-auth (2), keytext (6), login (6)