Similar to any digital dataset, a digital map is also vulnerable to modification, deliberate alteration and copyright violation. A map is a visual representation of a geographical area that is digitally stored in either raster or vector forms. Vector map is preferred over raster for both space optimization and quick processing time. Digest concept used for message authentication is extended to digitally watermark a digital map. The map digest triplet (M 1 dp , M 2 dp and M 3 dp ) is generated using various features of a digital map, supplier code and customer code. The approach computes two 160-bit hash values using secured hash algorithm (SHA1)and one 128-bit digest using message digest (MD5) algorithm. These two hash values of 160 bit and one digest of 128 bit are then embedded into a sequence of nodes of the map using graph theoretic approach in such a way that any alteration in the map alters the sub-graph. The sub-graph is the watermark. There are three watermarks.