We revise existing type-based analyses of security protocols by devising a core type system for secrecy, integrity and authentication in the setting of spi-calculus processes. These fundamental security properties are usually studied independently. Our exercise of considering all of them in a uniform framework is interesting under different perspectives: (i) it provides a general overview of how type theory can be applied to reason on security protocols; (ii) it illustrates and compares the main results and techniques in literature; (iii) perhaps more importantly, it shows that by combining techniques deployed for different properties, existing type-systems can be significantly simplified.