Computational soundness for key exchange protocols with symmetric encryption

Formal analysis of security protocols based on symbolic models has been very successful in finding flaws in published protocols and proving protocols secure, using automated tools. An important question is whether this kind of formal analysis implies security guarantees in the strong sense of modern cryptography. Initiated by the seminal work of Abadi and Rogaway, this question has been investigated and numerous positive results showing this so-called computational soundness of formal analysis have been obtained. However, for the case of active adversaries and protocols that use symmetric encryption computational soundness has remained a challenge.