The article introduces digital communication by drawing comparisons betweenthe histories of digital and conventional written communication. It also shows the technicaland legal bases and the currently reached achievements. In relation to the technicalelements, it acquaints the reader with the development and current effects of computertechnology, especially cryptography. In connection with the legal basis, the work presentsthe regulations which have emerged and made possible the legal acceptance of the digitalsignature and electronic documents in the United States of America, in the European Unionand among certain of its member countries, including Hungary. The article reviews theregulations and the developed practices in the fields of e-commerce, electronic invoices,electronic records management and certain e-government functions in Hungary which arenecessary for digital communication. The work draws attention to the importance of securekeeping and processing of electronic documents, which is also enforced by the legalenvironment. The author points to the technical requirements and practical troubles ofdigital communication, called digital sustainability.