The present invention relates to communications, and in particular though not exclusively to forming a secure connection between two untrusted devices. The present invention provides a method of securely connecting a first device (A) to a second device (B) using a third party authentication server (AS) coupled to the second device, the first device and the authentication server both having first device shared secret data (SSDa) and the second device and the authentication server both having second device shared secret data (SSDb). The method comprises receiving a request from the first device at the authentication server; the authentication server and the first device both generating a first device key (K_A) using the first device shared secret data in response to a first device random number (RANDa) sent from the authentication server to the first device; the authentication server and the second device both generating a second device key (K_B) using the second device shared secret data in response to a second device random number (RANDb) sent from the authentication server to the second device; and the authentication server securely forwarding to the second device (B) and the first device (A) a common key (K_AB) using the second and first device keys (K_B, K_A).