Reading the SIV RFC https://tools.ietf.org/html/rfc5297#page-9, I found that the S2V function starts by calculating the MAC of a "zero" block, doubles it and then XORs further data to the result.
Now looking at the BouncyCastle implementation, the exact same thing happens during the initialization of AES-CMAC.
How do I have to understand the S2V specification? Do I have to do all the "zero" stuff and doubling and XORing? Or does this already happen inside the AES-CMAC function? Would that mean, that AES-CMAC(key, plaintext) is equivalent to S2V(key, plaintext)?