Secure off-chain object delivery

Let's consider an example of a potential user (buyer) and merchant interaction using Polus Payments. The merchant intends to deliver a product to the user after receiving payment outside the blockchain. This example will be discussed within the context of EVM-compatible blockchains that utilize the Ethereum Virtual Machine (EVM). However, the overall architecture can be adapted to the specifics of other blockchain technologies if desired.

The merchant generates an invoice for payment, denoted as X, and communicates the invoice details to the user through some means. Once the user receives invoice X, they initiate the payment process by granting permission to spend tokens or by sending a specified amount N of the native token of blockchain T to smart contract Y. Taking into account the merchant's preferences, smart contract Y facilitates the immediate exchange of token T for token T`1 upon payment and reserves the corresponding funds in its balance.

Next, we have a group of validators, V1,V2,…,V(∞), which can represent various courier companies and delivery services. When the customer actually receives the product, confirmation from any responsible validator Vx is sufficient to validate the receipt of the item by the customer. Following this confirmation, smart contract Y transfers token T1 to the merchant's account on the blockchain. T can be equal to T`1.

$$X+N(T)→Y(T,T`1)→V`x→Y(T`1)$$

Where:

• X - represents the invoice for payment.

• N – denotes the amount of tokens T being sent.

• Y – signifies the smart contract that exchanges tokens T → $T`1.

• V`x – represents the validator confirming the customer's receipt of the item.

• Y(T'1) denotes the transfer of tokens T1 to the merchant's account.

And:

$$V`x∈{V`1,V`2,…,V(∞)}$$