only using public key cryptography, but using quantum mechanics as a support. This paper summarizes the current knowledge in the field of two-party cryptographic protocols devised f rom quantum systems. W e introduce the reader to the notion of cryptographic protocols and describe a number of sample building blocks to achieve them. W e also give pointers for the reader who i s interested to the quantum implementation of these building blocks. 2 Cryptographic Primitives We now introduce the main two basic primitives that have been widely considered as useful building blocks in the design of more elaborate cryptographic protocols: