A computer-implemented method for transmitting critical data between a client device and a server, comprising: dividing, at the client device, a first data structure intended for transmission to the server into at least a first data substructure containing critical data and a second data substructure that does not contain critical data, wherein the critical data comprises a plurality of personal and related data items stored together in the first data substructure and having restrictions related to the gathering, storage, accessing, dissemination and processing thereof by laws of a jurisdiction in which the client device is located; when the criticality of the data is based, at least in part, on finding at least two personal and related data items stored together in the first data substructure, dividing the first data substructure containing the critical data into at least a third and a fourth data substructures and placing one of the at least two personal data items into the third data substructure and the other of the at least two personal data items into the fourth substructure; transmitting the at least third and fourth data substructures to the server via a network node having a transformation module; and transmitting the second data substructure not containing critical data to the server bypassing the network node having the transformation module, wherein the second, third and fourth data substructures are combined into a second data structure at the server after being obtained, and wherein a primary transformation of the data substructures at the client is performed with no possibility of an inverse transformation of the data by the transformation module, wherein the transformation module performs a secondary transformation of the data substructure passing through the network node with no possibility of an inverse transformation at the server or the client device. dividing, at the client device, a first data structure intended for transmission to the server into at least a first data substructure containing critical data and a second data substructure that does not contain critical data, wherein the critical data comprises a plurality of personal and related data items stored together in the first data substructure and having restrictions related to the gathering, storage, accessing, dissemination and processing thereof by laws of a jurisdiction in which the client device is located; when the criticality of the data is based, at least in part, on finding at least two personal and related data items stored together in the first data substructure, dividing the first data substructure containing the critical data into at least a third and a fourth data substructures and placing one of the at least two personal data items into the third data substructure and the other of the at least two personal data items into the fourth substructure; transmitting the at least third and fourth data substructures to the server via a network node having a transformation module; and transmitting the second data substructure not containing critical data to the server bypassing the network node having the transformation module, wherein the second, third and fourth data substructures are combined into a second data structure at the server after being obtained, and wherein a primary transformation of the data substructures at the client is performed with no possibility of an inverse transformation of the data by the transformation module, wherein the transformation module performs a secondary transformation of the data substructure passing through the network node with no possibility of an inverse transformation at the server or the client device.