To date, there are numerous variants of designated verifier signatures (DVS), including the notion of strong DVS, multi DVS, universal DVS, etc. In this paper, for the first time, we present a generic definition of DVS model. We also explore the related security notions in DVS, including unforgeability, non-transferability and non-delegatability, and study the relationship of these notions against variants of DVS. Furthermore, we classify the multi designated verifier signature schemes into four categories depending on the way the verification and simulation is performed. We also point out some drawbacks on the existing DVS schemes, and finally present a new and efficient constant size multi DVS scheme that produces a constant size signature regardless the size of the receivers’ group. Our scheme is proven secure in the standard model