The controversies surrounding the right to privacy of individuals in a hyperconnected world are longstanding debates, where particular emphasis is placed on encryption technologies, which encode information by converting its original representations into alternative forms that computers cannot decipher, thus ensuring the security of communications. These technologies are at the heart of a public controversy, in which privacy advocates a clash with claims that encryption is a threat to general security as an enabler of subversive action. Recent developments in the armed conflict in Ukraine open up or renew questions such as: in times of war, what is the role of encryption and privacy technologies? How does armed conflict challenge existing threat models, what are the new risks for civil society? Can encryption save lives? This article addresses these questions by showing that encrypted messaging is the subject of convergence between the informational and physical aspects ‘in the field’ of war in the 21st century. The aim is to show how these messaging tools and the digital ecosystem that makes their deployment possible (interfaces, access providers, telecom operators) are now an integral part of a war and resistance infrastructure where the borders between cyber warfare and conventional warfare are becoming more and more blurred. However, we will also underline the limits of a tool-centred approach and demonstrate how, in the case of the war in Ukraine, physical threats to civilians and infrastructure damage mean that encrypted messaging is one among several innovative technical and social practices of holistic self-defence deployed by Ukrainians.