Wallet protocol

This is a project to define a new wallet protocol addressing problems with the current JSON-RPC implementation in bitcoind. Please feel free to make edits. If you disagree with something, turn it into a "debate".

Explanation

This protocol aims to be a standard for communication between Wallets and User Interfaces. It can be used to access a Wallet remotely, or even locally, even if the Wallet and User Interface are produced by different or competing vendors. For example, you could use an Android User Interface from Google to control a QBitcoin Wallet.

Please see the Infrastructure page for an overview of where this protocol fits into the big picture.

Requirements

• Never use human-formatted data (for example, use base bitcoin units, not Decimal BitCoins nor Tonal BitCoins, which should only be used in formatting for humans)
• Don't require polling (for example, broadcast events for new transactions, or changes to current "work")
• Cooperative mining (see below)
• Allow calculating expected minimum fee for transactions, with either (wallet's choice) locking on the used inputs, or prebuilding the tx and error if it becomes invalid before sending
• Easy to use in a RPC-like manner, for simple applications

Debates

Binary or plaintext

• Binary is more efficient to parse and create
• Plaintext is easier for humans to debug, and avoids forming a dependency on a specific number of bits, endianness, or precision
• Binary can include custom transactions as-is for transmission

Binary wire formats

• Protobuf seems efficient and easy to use from all major languages

Plaintext wire formats

• JSON implementations tend to be buggy. The biggest problem with JSON for financial applications is that many implementations allow only up to 53 bits of precision in numbers (see Twitter snowflake discussion). The alternative is to represent numbers as strings, but this moves parsing to the application layer which is undesirable.
• YAML (plaintext) is both human readable and efficient for parser (available for most PLs)

Cooperative mining

The protocol should support submitting completed blocks, such that it can get (just) addresses from an upstream pool to generate to, and send all completed blocks to that pool for verification and counting (and possibly submission to the network). This can reduce the pool's load.

UI bundling

For more secure use by ordinary end users, UIs and Wallets should support stream-based communication over standard I/O (stdio). This allows the UI to simply execute a dedicated Wallet, without requiring the user to setup Wallet-side authentication. This also permits full compatibility with a hardware-based wallet located on a secured device (for example, a cryptographic hardware module, or a wallet device connected via RS232 or USB). (Suggestion, if UI's could talk to any stream, including a child process's stdio, as well as a pipe or a device, the flexibility would be valuable)

DRAFT 0

Everything beyond this point is strictly DRAFT, should NOT be implemented, and is subject to being completely rewritten or modified!

Conformance requirements

All diagrams, examples, and notes in this specification are non-normative, as are all sections explicitly marked non-normative. Everything else in this specification is normative.

The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC2119. For readability, these words do not appear in all uppercase letters in this specification.

Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should", "may", etc) used in introducing the algorithm.

Transport/Session Layer

Must support at least reliable in-order stream data.

Such as:

• stdio (required for self-contained UI bundling)
• serial
• TCP

Presentation Layer

Encryption

• TLS (recommended)
• SSH

Packetization

Reliable, in-order packetization is required. Packets should be request-oriented, while supporting:

• Fixed-length responses (MIME-encoded)
• Persistent response streams (eg, HTTP chunked encoding)
• Optional: Full-duplex (two-way) communication (eg, WebSockets)

This supports:

• HTTP with SSE (and WebSockets)
• SPDY
• 0MQ, protobuf, and specialized .proto files

Request types:

• Optional: CONNECT for establishing a full-duplex stream
• GET for read-only access, always returning a fixed-length response
• POST for method calls
• PUT for uploads
• HEAD for metadata

Note: Some protocols (eg, HTTP) do not allow complex structures in GET requests. An implementation using these protocols should allow silently upgrading GET to a POST with the same semantics.

Note: A logical CONNECT request may not map directly to the HTTP method by the same name. The current WebSocket specification uses a HTTP GET request.

MIME Formats

These content types may be specified in the Content-Type header, and Accept header.

• application/x-www-form-urlencoded (required)
• application/x-ripemd-160 (required)
• application/x-sha (required)
• multipart/mixed (required)
• text/event-stream (required for events over HTTP)
• application/x-bitcoin (required wallet-side)
• application/json (recommended)
• application/xml

Application Layer

Authentication / security

Wallets may micro-manage security as they like, but the following are RECOMMENDED security levels:

"Miner"	Can generate new addresses, get work, and report found blocks
Merchant	Can create a transaction (only with 'proposal' flag), but not send it
Read-only	Can view accounts, addresses, and any public data, and combinations thereof (eg, balances)
Financial	Can create new transactions using the wallet's keys
Full/Admin	Can administrate (download, destroy, etc) wallet keys

Wallets MAY grant full access to username 'admin' with a null password, to requests over stdio.

Wallets SHOULD grant Merchant access to username 'merchant' will a null password, to requests made over direct (ie, physically local, like Bluetooth) connections. User interfaces SHOULD monitor for new, unsigned transactions with the 'proposal' flag set, and prompt the user to sign or delete them.

Object/Query Schema

May be provided in multipart/mixed, JSON, XML, etc...

Field Name	Blk	Tx	Accting	Coin	Key	Acct	Queryable	Description
id	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Unique data identifier; only guaranteed to remain the same for a single session
type	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Type of data: 'key', 'tx', 'coin', 'block', 'account', 'accounting'
hash	Yes	Yes	No	No	Yes	No	Yes
size	Yes	Yes	??	No	Yes	??	Yes
time	Yes	Yes	Yes	No	No	No	Yes
difficulty	Yes	No	No	No	No	No	Yes
difficultyNext	Yes	No	No	No	No	No	Yes
height	Yes	No	No	No	No	No	Yes
confirmations	Yes	Yes	??	Yes	No	No	Yes	-2 for rejected, -1 for unsent, 0 for broadcast, 1+ for number of confirms
accepted	??	Yes	??	Yes	No	No	Yes	An unconfirmed, accepted tx, is part of the current mining merkle tree
related	Yes	Yes	??	??	??	??	Yes	Can have multiple entries (in JSON, an array value)
coinbase	No	Yes	No	Yes	No	No	Yes
inputs	No	Yes	??	No	No	No	Yes
outputs	No	Yes	??	No	No	No	Yes
mine	Yes	Yes	??	Yes	Yes	??	Yes
network	Yes	Yes	??	Yes	Yes	??	Yes	0xF9BEB4D9 for the main network; 0xFABFB5DA for testnet
proposal	No	Yes	No	No	No	No	No

Data

• Arbitrary data can be accessed with the path /data/<id>
• GET to fetch
• To get only block header, use /data/<id>/header
• To get only actual content (eg, no calculated values), use /data/<id>/raw
• Optional: PUT to upload

Information

• GET /state/<network>/connections
• Mining info: (required for mining support)
  • GET /state/<network>/hashesPerSec (optional)
  • GET /state/<network>/merkle
• GET /info/protocols
  • Returns a list of supported protocols/versions and their URIs

Requests

Address validation

• GET /validate/address?network=<id>&address=<hash>

Calculate balance

• GET /balance?<query-object>

Match transactions to be included in the balance. To ignore spends, use matching.

Data search

• GET /dataSearch?<query-object>
• POST /dataSearch allowed for more complex queries

NOTE: To get the id rather than the data itself, use a HEAD request and check the Location header.

Generate new address

• POST /newAddress
  • Optional parameter: recycle (bool) -- allows wallet to reuse a spent change address; if not supported, wallet should silently ignore
  • Optional parameter: generate (bool) -- if true, make a new address on the spot, never use a preexisting one; if not supported, throw an error
  • Optional parameter: account -- associate new address funds with this account id

Monitor events

• Always POST

New data available

• Query

Move between accounts

• POST /accounting/move
  • dest=<accountId>
  • query=<query-object> OR amount=<amount>
  • Optional: comment=<string>

Transaction creation

• POST /tx/new
  • send (bool) -- If true, sign and broadcast the transaction immediately
  • fee (amount or range) -- If range, the wallet will try to calculate the minimum it expects the network to accept; if omitted, automatic fee range is unlimited unless bound by other factors (eg, input+strict)
  • Optional: fromAccount (account id)
  • Optional: input (multiple allowed of: coin id, OR coin id=>scriptSig)
  • output (multiple allowed of: address=>amount pairs, OR script=>amount)
  • strict (bool) -- If set, error rather than vary any parameters
  • Optional: comment=<string>

Transaction broadcast

• POST /tx/send?id=<existing-tx-internal-id>

Shutdown wallet

• POST /shutdown

p2p protocol encapsulation

Optional: Establish a full-duplex connection to /p2p to speak direct p2p protocol

Appendix A. Useful algorithms

Counting confirmations

Because numerous (most) transactions change confirmation at the same event, the only way to do this efficiently, is to monitor for new block events. When a block arrives, increment the confirmation count of all transactions with at least 1 confirmation already. Then check the new block's introduced transactions (incrementing them from 0 to 1), and delete/invalidate any revoked transactions (eg, from a competing chain).