The development of information society services presumes an effective, legally permitted and, when it comes to evidence, reliable tool enabling electronic communication and the archiving of electronic records and other written documents, in particular, contracts. Electronic written documents form a dominant part of the standard contracting processes today, both in public and private laws – a typical example of this are consumer contracts. The simplicity, speed, ergonomics, and overall efficiency of these contracting tools lead not only to electronic written documents being used more and more often than paper documents but also, among other things, to electronic written documents being used where other (traditional) forms of legal acting, predicated on tangible (paper) record carriers, were used before. Hence, electronic written documents and their new forms of signing penetrate practically in all legal spheres, even in those where traditional documents have never prevailed due to their ponderousness and various functional limitations. For these reasons, it seems appropriate and useful to analyse the importance of the behavioural and biometric methods inseparably associated with the signing of relevant electronic legal acts, as well as deal with related legal problems ensuing from the nature or the essence of use of these non-traditional electronic tools, including the crucial issue of their evidentiary reliability and actual protection in processing the sensitive personal data so generated.