Universal Hash Resolution Protocol

Ty Everett (ty@projectbabbage.com)


This document describes the Universal Hash Resolution Protocol (UHRP), a standard framework for content availability advertisement implemented with a UTXO-based overlay network. UHRP enables content hosts to advertise the availability of a particular file by creating a UTXO-based advertisement token, which is then submitted to the UHRP overlay and tracked by BRC-22 overlay network nodes. UHRP provides resilience to single points of failure and ensures content accessibility even if one host is offline, because multiple entities can be paid by content providers to keep content available.


In the digital world, consumers often require access to specific content without regard for the hosting source. Content providers, on the other hand, have a vested interest in maintaining wide availability of their offerings, even during host outages. Existing systems, however, do not provide a standardized and robust means of connecting users to their required files.

UHRP addresses this by enabling multiple content hosts to advertise the availability of content using UTXOs. Users can seek the content based on its hash, ensuring they connect to the files they need via an overlay network that is resilient to single points of failure. Content providers wishing to ensure consistent availability can pay multiple hosts, so that content remains available even if one host goes down.

This new paradigm not only streamlines content availability but also enables new hosts to build reputation by demonstrating opportunity cost (for example, by paying higher than normal transaction fees to miners on hosting commitments). Over time, service providers and applications can build a trusted list of UHRP hosts, thereby improving the overall reliability and trustworthiness of the content hosting ecosystem.


A UHRP advertisement token comprises a Bitcoin UTXO with a locking script containing the following components:

  • <public key>: This is the public key associated with the host that is making the advertisement.

  • OP_CHECKSIG: Ensures that if the token becomes spent, a signature was made using the host's private key.

  • Protocol prefix: A protocol prefix pushed onto the stack, with a value of 1UHRPYnMHPuQ5Tgb3AF8JXqwKkmZVy5hG.

  • <address>: The base58 version of the address corresponding to the <public key>.

  • <hash>: The next 32 bytes are the SHA-256 hash of the content being advertised.

  • <url>: The HTTPS URL where the host is advertising that the content is available for download.

  • <expiryTime>: A UTF-8 encoded version of a decimal integer representing the Unix timestamp of the advertisement expiry.

  • <contentLength>: A UTF-8 encoded version of a decimal integer representing the byte length of the content.

  • <signature>: A digital signature over the concatenated fields fields from the host's <public key>.

Upon creation and submission of an advertisement to a BRC-22 overlay network node for the UHRP topic, the node will track the UTXO and facilitate its lookup via a BRC-24 lookup service with the provider name UHRP. If the token ever becomes spent, the advertisement is canceled. The spending transaction may contain more information justifying the host's revocation (shch as a DMCA notice), but any such stipulation is beyond the scope of this initial document, and left for others to specify later.


Tools such as NanoSeek (for downloading) and NanoStore-Publisher (for uploading to a NanoStore provider) have been created by the Babbage team. To implement the serialization format, the uhrp-url tool can be used.

Questions about this initial draft specification should be directed to the author.

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