  We introduce new quantum key distribution protocols using quantum continuous
variables, that are secure against individual attacks for any transmission of
the optical line between Alice and Bob. In particular, it is not required that
this transmission is larger than 50 %. Though squeezing or entanglement may be
helpful, they are not required, and there is no need for quantum memories or
entanglement purification. These protocols can thus be implemented using
coherent states and homodyne detection, and they may be more efficient than
usual protocols using quantum discrete variables.
