BRFC ID Assignment

It is desirable that a BRFC document be uniquely identified. Without a central authority to issue an identification number, we have chosen to borrow inspiration from Bitcoin and use hashes of content.

ID Construction

To construct a BRFC ID from a specification, take the UTF8 string value of the title, author and version metadata fields (omit those not present), trim leading and trailing whitespace (leaving whitespace mid-way through the value), concatenate each value, then reinterpret the string as a byte array, and apply a double SHA256 hash.

let hash = sha256d(
  spec.title.trim() +
  ( || '').trim() +
  (spec.version || '').trim()

Hex-format the hash as per Bitcoin conventions (usually this means reversing the bytes before converting to hex).

let bitcoinDisplayHash = hash

Take the first 12 characters of the Bitcoin-style display hash (representing the last six bytes of the underlying sha256d value):

let brfcId = bitcoinDisplayHash.substring(0, 12);


Hashing the title, author and version metadata of a specification allows us to generate a unique ID without central authority. Hashing the entire specification was considered, however this was discounted due to the following drawbacks:

  • Any change, however minor (like typo fixes) would create an entirely new specification id
  • Different platforms handle line endings differently, and different source control and editor software can replace these without warning. This leads to unstable hashes across seemingly identical documents
  • Some file formats update metadata even when content remains unchanged. Again, this would lead to unstable hashes over otherwise stable content

Test Cases

title: BRFC Specifications
author: andy (nChain)
version: 1

Expected BRFC ID: 57dd1f54fc67

title: bsvalias Payment Addressing (PayTo Protocol Prefix)
author: andy (nChain)
version: 1

Expected BRFC ID: 74524c4d6274

title: bsvalias Integration with Simplified Payment Protocol
author: andy (nChain)
version: 1

Expected BRFC ID: 0036f9b8860f

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