Method for authenticating a Client in a Client-Server architecture, the method comprising a Model creation process, a Client creation process, and a Client authentication process; wherein, the Model creation process generates: (i) at the Client-side or at the Server-side, a Hierarchical model, shared between the Client and the Server, based on feeding a Regulated Activation Network computational model with a randomly generated N-dimensional input Dataset, said Hierarchical model comprised by a plurality of layers; the Client creation process generates: (i) at the Client-side or at the Server-side, a first Client's Encoded Passcode Hierarchy by feeding the Hierarchical model with a Client's passcode; the Client's Encoded Passcode Hierarchy being saved on the Server and comprises a set of encoded passcodes representing encoded versions of the Client's passcode; the Client's Encoded Passcode Hierarchy being formed by layers of the Hierarchical model, wherein each of said layers, except input layer, stores an encoded version from said encoded versions of the Client's passcode; (ii) at the Client-side or at the Server-side, a Policy for the Client's next authentication attempt, which is shared between the Client and the Server; and the Client authentication process: (i) generates, at the Client-side, a second Client's Encoded Passcode Hierarchy by feeding the Hierarchical Model with the Client's passcode and a Client's Encoded passcode is created using the Client's Encoded Passcode Hierarchy and the Policy shared between the Client and the Server; (ii) authenticates the Client at the server-side if the Client's encoded passcode, received from the Client, matches an expected encoded passcode generated at the server using the saved first Client's Encoded Passcode Hierarchy and the shared Policy; (iii) generates, at the Client-side or at the Server-side, a new Policy (5.1) if the Client is successfully authenticated, which is shared between the Client and the Server for the next Client's authentication attempt. the Model creation process generates: (i) at the Client-side or at the Server-side, a Hierarchical model, shared between the Client and the Server, based on feeding a Regulated Activation Network computational model with a randomly generated N-dimensional input Dataset, said Hierarchical model comprised by a plurality of layers; (i) at the Client-side or at the Server-side, a Hierarchical model, shared between the Client and the Server, based on feeding a Regulated Activation Network computational model with a randomly generated N-dimensional input Dataset, said Hierarchical model comprised by a plurality of layers; the Client creation process generates: (i) at the Client-side or at the Server-side, a first Client's Encoded Passcode Hierarchy by feeding the Hierarchical model with a Client's passcode; the Client's Encoded Passcode Hierarchy being saved on the Server and comprises a set of encoded passcodes representing encoded versions of the Client's passcode; the Client's Encoded Passcode Hierarchy being formed by layers of the Hierarchical model, wherein each of said layers, except input layer, stores an encoded version from said encoded versions of the Client's passcode; (ii) at the Client-side or at the Server-side, a Policy for the Client's next authentication attempt, which is shared between the Client and the Server; and (i) at the Client-side or at the Server-side, a first Client's Encoded Passcode Hierarchy by feeding the Hierarchical model with a Client's passcode; the Client's Encoded Passcode Hierarchy being saved on the Server and comprises a set of encoded passcodes representing encoded versions of the Client's passcode; the Client's Encoded Passcode Hierarchy being formed by layers of the Hierarchical model, wherein each of said layers, except input layer, stores an encoded version from said encoded versions of the Client's passcode; (ii) at the Client-side or at the Server-side, a Policy for the Client's next authentication attempt, which is shared between the Client and the Server; and the Client authentication process: (i) generates, at the Client-side, a second Client's Encoded Passcode Hierarchy by feeding the Hierarchical Model with the Client's passcode and a Client's Encoded passcode is created using the Client's Encoded Passcode Hierarchy and the Policy shared between the Client and the Server; (ii) authenticates the Client at the server-side if the Client's encoded passcode, received from the Client, matches an expected encoded passcode generated at the server using the saved first Client's Encoded Passcode Hierarchy and the shared Policy; (iii) generates, at the Client-side or at the Server-side, a new Policy (5.1) if the Client is successfully authenticated, which is shared between the Client and the Server for the next Client's authentication attempt. (i) generates, at the Client-side, a second Client's Encoded Passcode Hierarchy by feeding the Hierarchical Model with the Client's passcode and a Client's Encoded passcode is created using the Client's Encoded Passcode Hierarchy and the Policy shared between the Client and the Server; (ii) authenticates the Client at the server-side if the Client's encoded passcode, received from the Client, matches an expected encoded passcode generated at the server using the saved first Client's Encoded Passcode Hierarchy and the shared Policy; (iii) generates, at the Client-side or at the Server-side, a new Policy (5.1) if the Client is successfully authenticated, which is shared between the Client and the Server for the next Client's authentication attempt.