Proof of Assets

Proof of Assets specification and Javascript implementation.

Proof of Assets (PoA) is a scheme designed to let entitites (operators) prove that they control a given amount of Bitcoin or other blockchain based cryptocurrency.

The Proof of Assets scheme can be used as part of the broader Proof of Solvency scheme.

Proof of Assets online tools

Table of Contents

• Install
• Usage
• Specification
  • Serialized data formats (draft)
  • Implementations
  • Publishing protocol
  • Known limitations

WORK IN PROGRESS:

• Only supports bitcoind at the moment
• Doesn't support HD wallets yet

Install

npm install -g aproof

Usage

Generate asset proof

$ aproof signall -h "localhost" -p 8332 --user "rpcuser" --pass "rpcpass" "MtGox.com BTC assets" > btc-asset-proof.out.json

Verify signatures

$ aproof verifysignatures btc-asset-proof.out.json

Verify signatures and show total balance of all addresses

$ aproof balance -h "localhost" -p 8332 --user "rpcuser" --pass "rpcpass" btc-asset-proof.out.json

Browser build:

$ browserify ./lib/index.js --standalone aproof > build/aproof.js

Specification

WORK IN PROGRESS...

The assets proof is done by signing a message with all the private keys of a Bitcoin wallet or alternatively, with the private master key of an HD wallet and published alongside its chain code.

The message to sign is blockhash + '|' + message. Where + represents concatenation.

blockhash represents the latest block hash (with at least 6 confirmations) of the currency's blockchain.

This block hash can be used by verifiers to determine how long ago the PoA was produced. A PoA that was produced a long time ago could indicate that an operator lost the keys of its cold wallet for example.

Verifiers should issue warnings if a PoA is more than X (to be determined) days old or if the blockhash was omitted.

message is an arbitrary message (Proof of Solvency requires it to be the domain for which the proof is valid).

Serialized data formats (draft)

{
  "blockhash": "",
  "message": "",
  "currency": "BTC",
  "signatures": [
    { "signature": "", "address": "" },
    { "signature": "", "address": "", "chain": "" }
  ]
}

Implementations

Armory

See https://github.com/etotheipi/BitcoinArmory/pull/184/files

./extras/asset-proof.py  your.wallet "EmptyGox Btc Assets" emptygox-btc-assets.json

Publishing protocol

See olalonde/proof-of-solvency.

Known limitations

TODO... (you could convince someone else to signmessage for you?) There could be an online wallet which allows you to signmessage without revealing the private key, etc. etc. Might be interesting to explore the "make transaction"/"far future lock time" solution. Maybe combine multiple solutions together?