This European Telecommunication Standard (ETS) provides a description of the mechanisms necessary to provide adequate security within the Universal Personal Telecommunication (UPT) service for phase 1. It is based on the discussion and the conclusions of the general UPT security architecture given in ETR 083 [1]. In ETR 083 [1]@ the threat analysis leads to security features which are needed to counter the threats detected. Some of the threats are already countered by UPT service features. The security features and mechanisms against the remaining threats are discussed there for all UPT phases. In this ETS@ the specific security requirements@ features and mechanisms for UPT phase 1 are specified in detail. Clause 4 summarizes the phase 1 relevant security requirements and security features by means of general descriptions. Clause 5 specifies the security mechanisms@ especially for access control@ authentication and some security management aspects. Profiles are specified for weak and strong authentication@ respectively. Service limitations and other measures are recommended due to the restricted possibilities for the implementation of security features in UPT phase 1@ especially if only weak authentication is used. In clause 6@ the sizes and some values of the parameters used in the following clauses are given. clause 7 specifies the requirements for the UPT access device concerning input@ output@ data storage and the processing of data. Clause 8 contains the standardization of the exchanged data in the protocol for authentication. The security requirements for the Service Data Function (SDF) are specified in clause 9. Finally@ the options for the used authentication algorithm are discussed in clause 10. Only aspects of the UPT security architecture that concern the security of the overall UPT system or data exchanges with network components are standardized. Some security aspects need not be standardized@ e.g. the mechanism used for Device Holder Verification (DHV)@ bill limitation techniques@ the interface between the general part of the Dual Tone Multi Frequency (DTMF) device and its Security Module (SM)@ the subscription process and key management. They can be specified according to the service providers' needs@ provided that the general security requirements are considered. However@ examples and recommendations on how to realise these features are given in informative annexes. Upwards compatibility to later UPT phases is considered as far as useful and possible. This covers especially the use of IC cards as recommended for UPT phase 2.