Software called CoBo (Cooperative exploring and visualizing cryptographic protocols using concept keyboards), applies the principle of the "concept keyboard" to implement a system that supports the learning of cryptographic protocols. In previous research, concept keyboards (CK) were successfully used to implement a software system supporting the learning of classical algorithms, like QuickSort and Dijkstra's algorithm, among others. Traditional visualization software normally offers the learner an animated representation of the algorithm with the possibility of controlling the execution of the right steps, giving the learner a more or less passive role. Concept keyboards allow the learner to control the execution of the algorithm by deciding which function should be performed when. Four cryptographic protocols were implemented and tested (Wide Mouth Frog, Feige-Fiat-Shamir, Needham-Schroeder and Kerberos V). A it initial evaluation confirmed that the use of the CK fosters comprehension of the algorithms, facilitates the learning process and stimulates the learners' activity.