Cryptographic protocols are nowadays ubiquitous. They are used to protect monetary transactions, private data and all kinds of workflows that comprise our everyday and on-line life. Security breaches in these protocols are critical, but very often they could have been prevented by formally analyzing the security guarantees of the protocol before deployment. However, for being able to detect issues with protocols running over the internet already „on paper“, it is crucial to model this „internet“ as realistic as possible. In this talk, I will elaborate on how to obtain realistic security guarantees of cryptographic protocols, focussing on key exchange protocols.