Abstract: This paper describes a decipherment of the Indus script. The decipherment is based on observed similarities between Protocuneiform script and the Indus script. Meanings were transferred from Protocuneiform characters to characters in Indus script, and Dravidian words were used to obtain sounds for Indus script characters. Correlation between Brahmi letters and corresponding Indus characters were further used to correct the readings obtained. These readings show that Indus civilisation was largely Dravidian. It also shows that caste divisions specific to modern South India existed in Indus civilisation. Representative caste names can still be identified in North and South India. These readings also establish with a high probability that Protocuneiform script influenced the Indus script and that Brahmi script, at least partially, originated from the Indus script