In the current version of OST Platform, transactions will be validated through a Proof of Authority (PoA) consensus mechanism. Under PoA, the network consists of a permissioned set of trusted validators approved by OST to verify transactions. Under PoA, OST approves validators to join the network based on an assessment of how much skin in the game they have to run a secure and trusted network. The OST Platform is starting with PoA, first with OST as the only validator and then expanding to other permissioned validators, to provide for initial platform stability and to kick off the network and the economic incentives needed for validators to participate.
We are planning to decentralize the network in phases. Once the network is well established, we will transition validation to a completely decentralized Proof of Stake consensus mechanism as part of OpenST Mosaic. More details on OpenST mosaic can be found in its whitepaper here.