ref: 75c92428225428c8fde2d015f010e608a0b12f1d
dir: purgatorio/man/6/auth
.TH AUTH 6 .SH NAME auth \- authentication using station-to-station protocol .SH DESCRIPTION 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). .PP In the description below: .TF CERTx .PD .TP .I alpha is a Diffie-Hellman base used system wide .TP .I p is a Diffie-Hellman modulus used system wide .TP .I Rx is a random number of the same order as .IR p . .TP .BI PK x the public key of .I x .TP .BI SK x the private key of .I x .TP .BI CERT x the public key of .I x signed by the certifying authority .TP .BI sig n ( x ) represents .I x signed with .IR n 's private key .PP In the following, the parties are labelled 0 and 1. .PP Each sends its public key and certificate to the other together with a computation .IR "alpha**r0 mod p" .RI ( "alpha**r1 mod p" ) based on the Diffie-Hellman parameters contained in the certificate: .IP .EX 0 → 1 alpha**r0 mod p, CERTu0, PKu0 1 → 0 alpha**r1 mod p, CERTu1, PKu1 .EE .PP Each can now use the CA's public key and the certificate received to check that each has the other's public key. .PP Finally, each user signs values known to both that each can then verify: .IP .EX 0 → 1 sig0(alpha**r0 mod p, alpha**r1 mod p) 1 → 0 sig1(alpha**r0 mod p, alpha**r1 mod p) .EE .PP At this point 0 and 1 can calculate the shared secret .BR "alpha**(r0*r1)" , and can use it to encrypt later communications. .SH SEE ALSO .IR keyring-auth (2), .IR keytext (6), .IR login (6)