A high-frequency surgical testing device for testing a neutral electrode during treatment, particularly during monopolar coagulation of biological tissue using a high-frequency current. The described multi-dimensional cryptographic methods comprise forming a first keystream being assigned to a first dimension of the dataset and forming a second keystream being assigned to a second dimension of the dataset. This system provides a high level of encryption security equivalent to that provided by public keyasymmetric cryptography without the complexity and expense of the associated PKI infrastructure.