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ADBC Transaction Access Point - Gateway (TAP-GW) Specification

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  • Editor: Chris Gough
  • Contributors: Steve Capell


phrase Definition
ausdigital-tap/2 Version 2 of the AusDigtial TAP specification

This document describes the access point gateway (TAP-GW), which is an optional extension to the ausdigital-tap/2. The TAP-GW allows ledger implementers to standardise interfaces and protocols for communication between trusted/secure ledger systems and public-facing TAP services.


This spec is a requirement for consultation.

If a trusted business system is persistently connected to the internet and natively supports the TAP protocol, then it has no need for TAPGW interface, either as a client or server. Gateways are not necessary in the TAP protocol, the TAPGW sub-protocol is described as an optional extension to the TAP protocol.

There are various reasons why a business system architect may want a structural separation between their trusted components (e.g. ledger service, ERP system, etc) and their externally facing components, such as a TAP Gateway. These include performance, reliability and security objectives, as well as a desire to focus on features that differentiate their system while outsourcing generic functionality to services with low-cost utility characteristics. The TAPGW sub-protocol is designed to ensure Gateway services are generic and interchangeable commodities.

A TAP Gateway service is an availability mediator (allowing trusted business system components to have intermittent connectivity, and/or to sit behind a firewall). It is however more than a simple asynchronous proxy (store-and-forward service); additionally, it performs functions such as message validation, logging, access control, and protocol callbacks (including to Notary services).

Cryptography is used to prevent TAP Gateways from being able to inspect or manipulate the content of business messages. A TAP Gateway is not custodian of any business key material, it is only trusted to reliably send and receive messages. Message signing and encryption/decryption is performed by systems behind TAPs. The TAP is unable to verify signatures that have been encrypted, but can verify signatures that are not encrypted.

Notarisation to the blockchain makes it possible for the business system to audit the reliability of any TAP Gateway that it uses.

This specification aims to support the Australian Digital Business Council eInvoicing initiative, as an extension of the It is under active development at


Copyright (c) 2016 the Editor and Contributors. All rights reserved.

This Specification is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This Specification is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, see

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This document is governed by the 2/COSS (COSS).


The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.