A security ceremony expands a security protocol with everything that is considered out of band for it. Notably, it incorporates the user, who, according to their belief systems and cultural values, may be variously targeted by social engineering attacks. This makes ceremonies complex and varied, hence the need for their formal analysis aimed at their rigorous understanding.Formal analysis in turn requires clarifying the ceremony structure to build a ceremony model. The model defined here spans over a number of socio-technical layers, ranging from a computer network to society. It inspires a layered analysis of security ceremonies, that is layer by layer. This paper focuses on the human-computer interaction layer, which features a socio-technical protocol between a user persona and a computer interface. Future work will be to traverse all layers by formal analysis.