"ka" for a genitive suffix

I've always been curious about the origin of -ka, -ke, -ki, which are clitics (or postpositions) that are declined to agree in number and gender with the possessed noun (phrase). I took a look round, and see that they are traced back to Sanskrit participle क्र्त (kRta) 'done, made' > Prakrit kera; cf. Sanskrit कपिक्र्तम् वचनम् (kapikRtaM vacanaM) 'monkey-made speech'. (In my imagination, I had assumed it was some adjectival ending from Sanskrit.)

Ceci n'est pas un seing.