A proper authentication mechanism is the very basic requirement for building a secure environment. Recently, a lot of effort has been invested in development of various types of authentication mechanisms that offer strong security characteristics for building grid systems. Being based on one of the mechanisms, most grid environments today provide strong authentication protocols, however, they are usually bound with only one, in most cases based on public key infrastructure (PKI). Such an arrangement works pretty well, but unnecessarily limits users since they are required to use only the one mechanism, which may not be flexible or convenient. A better solution would be to offer users a freedom to choose their own authentication mechanism and provide automatic translations that guarantee that all services and components are securely available regardless of the choice of authentication mechanism. In this paper we provide a survey of authentication mechanisms that are used in current grids and other distributed systems and discuss transition mechanisms between them.