This book constitutes the refereed proceedings of the 34th Conference on Current Trends in Theory and Practice of Computer Science, SOFSEM 2008, held in Slovakia, in 2008. The 57 revised full papers, presented together with 10 invited contributions, were carefully reviewed and selected from 162 submissions. The contributions are segmented into four topical sections on foundations of computer science; computing by nature; networks, security, and cryptography; and Web technologies.