# ePBS future vs today?

## How does the PBS landscape look like today?

**Actors:** Proposer and Out of protocol trusted relays

**Bid Sourcing Avenues:** Proposers can only source bids from trusted relays via the Builder-API.

**Bid Structures:** A Proposer requests a [SignedBuilderBid](https://github.com/ethereum/builder-specs/blob/main/types/electra/bid.yaml#L23) from the relays.
It creates a [BlindedBeaconBlock](https://github.com/ethereum/beacon-APIs/blob/339eea96b41c787dad47765fc781303fb40aa886/types/electra/block.yaml#L90) which it returns to the relays. The relays are responsible for constructing the full [SignedBeaconBlock](https://github.com/ethereum/beacon-APIs/blob/339eea96b41c787dad47765fc781303fb40aa886/types/electra/block.yaml#L68) and publishing it to the network.

**Proposer Payment:** The builders pay the proposer through a transaction in the execution payload. This is usually the last transaction in the payload. Proposers trust the relay to ensure that the payment is being made.

**Payload Revelation:** Once the proposer has sent the [SignedBlindedBeaconBlock](https://github.com/ethereum/beacon-APIs/blob/339eea96b41c787dad47765fc781303fb40aa886/types/electra/block.yaml#L100) to the relay, the relay can reveal the beacon block with the full payload to the network without getting unbundled.

**How to become a builder**: To become a builder, you require to build BuilderBids and submit it to the relays. This is completely permissionless and anyone can submit their bids to the relays.

## How does the landscape change with ePBS?

**Actors:** Proposers and Enshrined Builders.

**Bid Sourcing Avenues:** A bid can be sourced via the Builder-API which is a lower latency direct TCP connection with the builder. It can also be sourced from the P2P network via the [execution_payload_bid](https://github.com/ethereum/consensus-specs/blob/master/specs/gloas/p2p-interface.md#execution_payload_bid) gossip topic.

**Bid Structures:** A proposer receives an `SignedExecutionPayloadBid` from the builder. It embeds the best `SignedExecutionPayloadBid` available to it in the `BeaconBlockBody`. The builder then constructs a `SignedExecutionPayloadEnvelope` and broadcasts it to the PTC commitee. The `SignedBeaconBlock` with the bid is broadcasted to the PTC commitee.

**Proposer Payment:** Proposer payments can be done via the execution payload as it is done today by specifying the payment value in the `bid.execution_payment` field. Builders can also pay proposers via a trustless payment by specifying the payment value in the `bid.value` field. The trustless payment is paid from the builder's staked collateral.

**Payload Revelation:** When a builder's bid is selected by a proposer to be included in a BeaconBlock, the builder has to construct a `SignedExecutionPayloadEnvelope` and broadcast it to the PTC commitee to ensure its timeliness. The builder can choose to broadcast the `SignedExecutionPayloadEnvelope` only if the associated beacon block has received enough attestations.

**How to become a builder**: ePBS enshrines builders and to be able to submit bids to the proposer, builders require to stake a minimum of 1ETH collateral on the beacon chain.