RFID technology increases rapidly its applicability in new areas of interest without guaranteeing security and privacy issues. This paper presents a new architecture of an RFID transponder with cryptographic capabilities. Other than being compatible with the EPC Class-1 Gen-2 communication protocol, our tag implements an asymmetric ciphering module that proved useful in authentication and anti-counterfeit schemes, particularly critical in many application fields. Experimental results concerning area requirements and power consumption indicate its feasibility. Categories and Subject Descriptors C.3 [Special-Purpose and Application-Based Systems]; B.5.1 [Register-Transfer-Level Implementation]: Design. General Terms Design, Security. Keywords RFID, privacy, authentication.