1.  YS-1 The PIC Pre-IKE Credential Provisioning Protocol Yaron Sheffer (RADGUARD) and Hugo Krawczyk (Technion) March 2000

2.  YS-2 Overview  PIC is a method to provide credentials, based on legacy authentication  Credentials to be used in a later IKE session  Separate Authentication Server (AS)  Flexible: authentication methods, credentials  Based on a dedicated, ISAKMP-based mechanism, plus XAuth  No modifications to IKE! –But significant reuse

3.  YS-3 Protocol Entities Client/User Authentication Server (AS) Legacy Authentication Server (LAS) Security Gateway (SGW) Optional Link

4.  YS-4 Separate Authentication Server  Eliminate user authentication from SGW –Simplified SGW can be used with/without PKI  DoS attack on AS will not break existing connections at SGW  AS may or may not be collocated with SGW  User authenticates once for many gateways

5.  YS-5 PIC Protocol Stages 1. Establish a one-way authenticated secure channel –Only server is authenticated 2. Authenticate user –Typically assisted by legacy server 3. Hand out credentials to user  Architecture similar to draft-bellovin-ipsra- getcert-00

6.  YS-6 (Somewhat) Detailed Protocol Client sends –HDR, SA, KE, Ni –Message 2 of XAuth –Credential request over XAuth AS sends –HDR, SA, KE, Nr, IDr1,[ CERT, ] SIG_R –Message 1 of XAuth –User credentials Calculate SKEYID Possibly more...

7.  YS-7 User Authentication Methods Anything that XAuth supports, for example:  Simple authentication  Challenge/response  Two-factor authentication  One-time password Note: may need to add machine authentication

8.  YS-8 Credentials  Certificate signing user’s public key –Possibly short-term  User certificate and private key  Shared secret –Requires channel between AS and SGW (adds protocol complexity) –Significantly improves DoS-resistance of SGW

9.  YS-9 Summary  Outlined PIC, a protocol to enable remote users to initiate an IKE exchange  Reusing XAuth mechanisms and existing IKE code  PIC is a practical alternative if IPSRA chooses a separate authentication server

10.  YS-10 References  PIC: draft-ietf-ipsra-pic-00.txt  XAuth: draft-ietf-ipsec-isakmp-xauth-06.txt  IPSRA requirements: draft-ietf-ipsra-reqmts-00  Credentials over TLS: draft-bellovin-ipsra-getcert-00

11.  YS-11 Backup

12.  YS-12 Obtaining the AS Public Key  Needed at client anyway to initiate IKE  Much easier to distribute a site certificate than build a full-blown PKI  Alternatively, can tunnel EKE over PIC and pass server’s cert as part of credential –Client should trust the AS only when EKE exchange is over (complexity!) –Somewhat inefficient...