BitStream: Atomic data exchange protocol.

23-11-16 12:51

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Original Title: "BITSTREAM: A PROTOCOL FOR ATOMIC DATA EXCHANGE"

Author: Shinobi

Compiled by: Luccy, BlockBeats

Editor's Note:

On November 12th, Robin Linus, the project leader of ZeroSync and developer of BitVM, published an article titled "BitStream: Decentralized File Hosting Incentivized by Bitcoin Payments", proposing a decentralized file hosting incentive protocol called BitStream, which provides a sustainable alternative. For example, a user may only upload a video once, generating a one-time fee, but if that video becomes very popular and is downloaded 100,000 times, the server's bandwidth costs may far exceed the initial upload revenue.

BitStream's pay-per-download method provides a solution: it allows servers to charge for each download, ensuring that revenue expands with the popularity and demand of the media, creating a balanced and profitable ecosystem.

BitStream uniquely hashes all files, emphasizing the importance of the verification process in the context of atomic file purchases. Compared to Filecoin and BitTorrent, BitStream avoids unnecessary altcoins and over-designed technical protocols, focusing on solving practical needs.

Shinobi, a self-taught educator in the Bitcoin field, describes in detail the workings of the BitStream protocol, emphasizing that file sellers can use innovative methods to encrypt and sign files to improve fraud proof efficiency. By constructing a special encrypted file tree, the validity of files can be more effectively verified.

The idea of using digital currency to atomically purchase digital files has a long history in this industry. Digital goods and digital currency seem to be a perfect match. Digital goods, namely information, are also a huge market. Imagine all the videos, audios, texts, games, and other forms of digital content that people regularly purchase and consume, their market value reaching billions of dollars, and people interact in these markets every day.

Most attempts to implement paid file sharing have gone down the wrong path. Filecoin attempted to achieve this goal on top of IPFS, but the project was ultimately designed to be ridiculous. BitTorrent (the company, not the protocol) was acquired by Justin Sun and integrated with its own cryptocurrency and blockchain. Neither of these projects has made substantial progress technically, and they are over-designed technically with questionable economic incentives.

BitStream is a proposal put forward by Robin Linus, attempting to address the need for atomic purchasing of data without unnecessary alternative coins and overly designed technical protocols.

All files can be uniquely identified by a single hash in this scheme, which is a very important detail. Atomic sales of files require encryption of the files using a function that allows users to verify the encrypted content, after which users purchase the encryption key for the file atomically. The problem lies in the verification process, and more importantly, proving whether or not one has been deceived and that the decrypted data is incorrect is expensive. Simply put, you need to generate the entire encrypted file and decryption key so that others can decrypt and verify that the decrypted data matches the expected hash value.

File sharing systems like BitTorrent often divide files into standard-sized blocks and construct a Merkle tree, which allows the root hash to serve as a file identifier in magnet links and verify that each individual block you download is a valid part of the file. This is a property that can be leveraged to greatly improve the efficiency of fraud proofs, demonstrating that file distributors have deceived you.

The seller of the file can generate a random value and use it to encrypt each file block by performing an XOR operation on the random value. Then, they can sign a declaration containing the encrypted file root hash and encrypted value hash. The encrypted file tree is set up in a special way to simplify fraud proof.

Instead of just constructing a merkle tree of normal file blocks, this tree creates pairs of encrypted file blocks and their adjacent unencrypted file blocks' hashes. Now, buyers can download the encrypted file and atomically purchase the decryption value by obtaining all unencrypted block hashes and creating a merkle tree from them to ensure they match the root hash of the unencrypted file. This is achieved by the seller using it as the preimage for an HTLC on the Lightning Network or as the preimage for Chaumian eCash minting that supports HTLCs, such as Cashu.

If the file decryption is incorrect, it is either because the encrypted data is from another file or because the preimage is not the actual encryption key. In this case, the Merkle path from any two leaves in the encrypted file tree can reveal that the seller has deceived the buyer. Providing the path to any encrypted file block and its corresponding unencrypted block hash, along with the preimage that the buyer purchased, will clearly prove that the seller did not provide the file they claimed to the buyer.

Any file seller using the BitStream protocol can deposit a collateral, which can be slashed with a fraud proof if they deceive their customers, as designed above. In the simplest case, this can be done by depositing collateral in a Chaumian Mint. Platforms like Liquid offer alternative methods to build trustless execution using features like OP_CAT. Scripts can be built to actually accept BitStream fraud proofs and verify them on the stack, allowing for the creation of a UTXO spendable by anyone with a valid fraud proof. If OP_CAT becomes available on the main chain, it may even be possible to operate without a federated execution environment.

BitStream is a very promising protocol for atomically selling digital information, with a highly efficient fraud-proof scheme and no need for junk coins.