Shopping in the real world gives one the chance to maintain their privacy, by using cash; thus, revealing no personal data such as one’s name, address…etc. Oppositely, shopping online mandates providing all sorts of private data for billing and/or shipping purposes. Even though cryptocurrencies, such as bitcoin, have provided a revolutionary private billing solution, via enabling pseudonymous transactions, anonymous shipping of purchased merchandise is still a problem that is yet to be solved.
A recently published paper presented a novel blockchain based system for delivering purchased goods, called Lelantos that has been proven, through experimental trials, to offer buyer’s anonymity, fair exchange and seller-buyer unlinkability. The system is inspired by Tor’s onion routing approaches which are used to promote anonymity across the Tor network. Moreover, Lelantos utilizes blockchain pseudonymity and decentralization, in order to provide pseudonymous delivery of goods that is almost impossible to trace back. Lelantos also utilizes smart contracts’ distributed consensus mechanisms to impose fair indisputable transactions between trustless contractual parties.
An Overview of Lelantos:
Lelantos is a physical delivery system that relies on the blockchain technology to preserve the anonymity of both sellers and buyers. The system implements a package routing approach via several delivery companies. Lelantos is a combination of three elements:
1. An interface that relies on blockchain smart contracts to intermediate the process of delivery of items in a fairly anonymous means, without having to rely on any intermediary or third party.
2. A web based service to advertise and register potential delivery companies that can offer the requested service.
3. Contractual applications to monitor the state and progress of smart contracts and interact accordingly with them as per the contractual party’s role.
The creators of Lelantos defined the functionality of the system’s smart contract and other offchain elements, while focusing on minimizing onchain operations to reduce onchain execution of code to minimize gas expenditure. On the other hand, they analyzed the security of the basic elements of the system according to anonymity; fair exchange; unlinkability between buyers and sellers and unauthorized pickup. A working prototype of Lelantos’ smart contract is implemented, as a proof of concept, in the form of an open source project that is available as a github repository. The anonymous delivery system is designed on the basis of an operational threat model that provides the following features:
a. Fair exchange: The anonymous package delivery system is moderated by the means of a decentralized smart contract that guarantees fair transmission of funds to both sellers and delivery companies, and that the right package is delivered to its pre-intended customer.
b. Buyers’ anonymity: Customers needn’t reveal any private information other than their pseudonym to any of the contractual parties (i.e. sellers and delivery companies).
c. Seller-buyer unlinkability: any contractual party will have knowledge of no more than two hops of the package routing trip, which renders it almost impossible to link the buyer to the seller.
The smart contract used by Lelantos is an Ethereum based smart contract written in Solidity. The smart contract enables customers to choose the route throughout which the package would be shipped via a group of N of n delivery companies of his/her choice. For each chosen delivery company, the customer will prepare an encrypted message that includes a tracking number of his/her choice along with the address of the next delivery company concealed by another tracking number of his/her choice too. All text sent is encrypted via the smart contract, so the tracking numbers will be only meaningful to the customer. In other words, all information regarding the package shipping route, number of delivery companies will be concealed, except for the customer and each two consecutive delivery companies. With the recent rise in the price of ethereum, ether gas price has risen too. To execute a smart contract on ethereum’s blockchain, one must pay for the computational resources’ expenditure throughout the process by paying ether gas. To minimize ether gas expenditure, Lelantos is designed to minimize onchain code execution by leveraging offchain solutions.
Lelantos is by far the first attempt to provide a blockchain based anonymous package delivery system. If this system comes into life, dark web marketplaces will be the most to benefit from it.