Publishing

Publishing is the act of broadcasting a vendor's data to the Bitcoin blockchain. Once a vendor's data has been published, anyone can retrieve his/her data by supplying the xpubkey.

At a high level, the vendor data is compressed into a msgpack byte array, signed, and split into 37-byte chunks called "manifest chunks". Each manifest chunk is given a 3-byte header for a total of 40-bytes.

The following is pseudocode to help understand the publishing process.

//pack the vendor data using the msgpack encoding scheme
vendorDataMsg = msgpack.encode(vendorData)

//sign the vendor data with the vendor's address
signature = sign(vendorDataMsg,vendor.address)

//compute the number of transactions a broadcast will take
transactionsRequired = ((1+vendorData)/37).roundUp()

//the publishing algorithm can only handle up to 255 transactions
if(transactionsRequired>255) throw 'Too many transactions required'

//add everything together into a single byte array
manifest = [transactionsRequired] + signature + vendorDataMsg 

//split the bytes into chunks of 37
manifestChunks = manifest.splitIntoChunksOfByteSize(37)

//determine the random byte (byte #2 of the 3 byte header)
randomByte = random(0,255)

//create an OP_RETURN transaction for each chunk and broadcast it to the network
manifestChunks.each(function(vendorDataMsgChunk,index){
    sendrawtransaction('OP_RETURN',header(randomByte,index)+vendorDataMsgChunk,vendor.address)
})

Vendor Data

All fields are to be decoded using UTF8. Only the product image url is optional.

• Name (n)
• Currency (c)
• Pgp Key Data (k)
• Info (i)
• Array of Products (p)
  • Name (n)
  • Price (p) (string)
  • Image URL (i) (optional)

Manifest Chunk Headers

Each manifest chunk contains a 3 byte header.

1. A constant 0x6D to indicate a manifest chunk. 0x6D is the hex code for m.
2. A random hex between 0x00 and 0xff. This is to help protect against manifest chunks from different manifests from being comingled.
3. The index of the manifest chunk in the manifest. For example the first chunk would have a header of 0x00 while the second one would have a header of 0x01.