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+
+This manual is for the GNU Taler merchant backend (version 0.5.0, 17
+August 2019),
+
+Copyright © 2016, 2017, 2019 Taler Systems SA
+
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3 or
+ any later version published by the Free Software Foundation; with no
+ Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+ Texts. A copy of the license is included in the section entitled “GNU
+ Free Documentation License”.
+
+The GNU Taler manual for Web shops
+##################################
+
+This manual is for the GNU Taler merchant backend (version 0.5.0, 17
+August 2019),
+
+Copyright © 2016, 2017, 2019 Taler Systems SA
+
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3 or
+ any later version published by the Free Software Foundation; with no
+ Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+ Texts. A copy of the license is included in the section entitled “GNU
+ Free Documentation License”.
+
+Introduction
+============
+
+About GNU Taler
+---------------
+
+GNU Taler is an open protocol for an electronic payment system with a
+free software reference implementation. GNU Taler offers secure, fast
+and easy payment processing using well understood cryptographic
+techniques. GNU Taler allows customers to remain anonymous, while
+ensuring that merchants can be held accountable by governments. Hence,
+GNU Taler is compatible with anti-money-laundering (AML) and
+know-your-customer (KYC) regulation, as well as data protection
+regulation (such as GDPR).
+
+GNU Taler is not yet production-ready, after following this manual you
+will have a backend that can process payments in “KUDOS”, but not
+regular currencies. This is not so much because of limitations in the
+backend, but because we are not aware of a Taler exchange operator
+offering regular currencies today.
+
+.. _About-this-manual:
+
+About this manual
+-----------------
+
+This tutorial targets system administrators who want to install a GNU
+Taler merchant *backend*.
+
+We expect some moderate familiarity with the compilation and
+installation of free software packages. An understanding of cryptography
+is not required.
+
+This first chapter of the tutorial will give a brief overview of the
+overall Taler architecture, describing the environment in which the
+Taler backend operates. The second chapter then explains how to install
+the software, including key dependencies. The third chapter will explain
+how to configure the backend, including in particular the configuration
+of the bank account details of the merchant.
+
+The last chapter gives some additional information about advanced topics
+which will be useful for system administrators but are not necessary for
+operating a basic backend.
+
+.. _Architecture-overview:
+
+Architecture overview
+---------------------
+
+crypto-currency
+KUDOS
+Taler is a pure payment system, not a new crypto-currency. As such, it
+operates in a traditional banking context. In particular, this means
+that in order to receive funds via Taler, the merchant must have a
+regular bank account, and payments can be executed in ordinary
+currencies such as USD or EUR. For testing purposes, Taler uses a
+special currency “KUDOS” and includes its own special bank.
+
+The Taler software stack for a merchant consists of four main
+components:
+
+- frontend
+ A frontend which interacts with the customer’s browser. The frontend
+ enables the customer to build a shopping cart and place an order.
+ Upon payment, it triggers the respective business logic to satisfy
+ the order. This component is not included with Taler, but rather
+ assumed to exist at the merchant. This manual describes how to
+ integrate Taler with Web shop frontends.
+
+- back office
+ A back office application that enables the shop operators to view
+ customer orders, match them to financial transfers, and possibly
+ approve refunds if an order cannot be satisfied. This component is
+ again not included with Taler, but rather assumed to exist at the
+ merchant. This manual will describe how to integrate such a component
+ to handle payments managed by Taler.
+
+- backend
+ A Taler-specific payment backend which makes it easy for the frontend
+ to process financial transactions with Taler. The next two chapters
+ will describe how to install and configure this backend.
+
+- DBMS
+ Postgres
+ A DBMS which stores the transaction history for the Taler backend.
+ For now, the GNU Taler reference implemenation only supports
+ Postgres, but the code could be easily extended to support another
+ DBMS.
+
+The following image illustrates the various interactions of these key
+components:
+
+::
+
+ Missing diagram image
+
+RESTful
+Basically, the backend provides the cryptographic protocol support,
+stores Taler-specific financial information in a DBMS and communicates
+with the GNU Taler exchange over the Internet. The frontend accesses the
+backend via a RESTful API. As a result, the frontend never has to
+directly communicate with the exchange, and also does not deal with
+sensitive data. In particular, the merchant’s signing keys and bank
+account information is encapsulated within the Taler backend.
+
+Installation
+============
+
+This chapter describes how to install the GNU Taler merchant backend.
+
+Installing Taler using Docker
+-----------------------------
+
+This section provides instructions for the merchant backend installation
+using ‘Docker‘.
+
+For security reasons, we run Docker against a VirtualBox instance, so
+the ``docker`` command should connect to a ``docker-machine`` instance
+that uses the VirtualBox driver.
+
+Therefore, the needed tools are: “docker“, “docker-machine“, and
+“docker-compose“. Please refer to Docker’s official [1]_ documentation
+in order to get those components installed, as that is not in this
+manual’s scope.
+
+Before starting to build the merchant’s image, make sure a
+“docker-machine“ instance is up and running.
+
+Because all of the Docker source file are kept in our “deployment“
+repository, we start by checking out the ``git://taler.net/deployment``
+codebase:
+
+::
+
+ $ git clone git://taler.net/deployment
+
+Now we actually build the merchant’s image. From the same directory as
+above:
+
+::
+
+ $ cd deployment/docker/merchant/
+ $ docker-compose build
+
+If everything worked as expected, the merchant is ready to be launched.
+From the same directory as the previous step:
+
+::
+
+ # Recall: the docker-machine should be up and running.
+ $ docker-compose up
+
+You should see some live logging from all the involved containers. At
+this stage of development, you should also ignore some (harmless) error
+message from postresql about already existing roles and databases.
+
+To test if everything worked as expected, it suffices to issue a simple
+request to the merchant, as:
+
+::
+
+ $ curl http://$(docker-machine ip)/
+ # A greeting message should be returned by the merchant.
+
+.. _Generic-instructions:
+
+Generic instructions
+--------------------
+
+This section provides generic instructions for the merchant backend
+installation independent of any particular operating system. Operating
+system specific instructions are provided in the following sections. You
+should follow the operating system specific instructions if those are
+available, and only consult the generic instructions if no
+system-specific instructions are provided for your specific operating
+system.
+
+.. _Installation-of-dependencies:
+
+Installation of dependencies
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The following packages need to be installed before we can compile the
+backend:
+
+- autoconf >= 2.69
+
+- automake >= 1.14
+
+- libtool >= 2.4
+
+- autopoint >= 0.19
+
+- libltdl >= 2.4
+
+- libunistring >= 0.9.3
+
+- libcurl >= 7.26 (or libgnurl >= 7.26)
+
+- GNU libmicrohttpd >= 0.9.39
+
+- GNU libgcrypt >= 1.6
+
+- libjansson >= 2.7
+
+- Postgres >= 9.4, including libpq
+
+- libgnunetutil (from Git)
+
+- GNU Taler exchange (from Git)
+
+Except for the last two, these are available in most GNU/Linux
+distributions and should just be installed using the respective package
+manager.
+
+The following sections will provide detailed instructions for installing
+the libgnunetutil and GNU Taler exchange dependencies.
+
+.. _Installing-libgnunetutil:
+
+Installing libgnunetutil
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+GNUnet
+Before you install libgnunetutil, you must download and install the
+dependencies mentioned in the previous section, otherwise the build may
+succeed but fail to export some of the tooling required by Taler.
+
+To download and install libgnunetutil, proceed as follows:
+
+::
+
+ $ git clone https://gnunet.org/git/gnunet/
+ $ cd gnunet/
+ $ ./bootstrap
+ $ ./configure [--prefix=GNUNETPFX]
+ $ # Each dependency can be fetched from non standard locations via
+ $ # the '--with-<LIBNAME>' option. See './configure --help'.
+ $ make
+ # make install
+
+If you did not specify a prefix, GNUnet will install to ``/usr/local``,
+which requires you to run the last step as ``root``.
+
+.. _Installing-the-GNU-Taler-exchange:
+
+Installing the GNU Taler exchange
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+exchange
+After installing GNUnet, you can download and install the exchange as
+follows:
+
+::
+
+ $ git clone git://taler.net/exchange
+ $ cd exchange
+ $ ./bootstrap
+ $ ./configure [--prefix=EXCHANGEPFX] \
+ [--with-gnunet=GNUNETPFX]
+ $ # Each dependency can be fetched from non standard locations via
+ $ # the '--with-<LIBNAME>' option. See './configure --help'.
+ $ make
+ # make install
+
+If you did not specify a prefix, the exchange will install to
+``/usr/local``, which requires you to run the last step as ``root``.
+Note that you have to specify ``--with-gnunet=/usr/local`` if you
+installed GNUnet to ``/usr/local`` in the previous step.
+
+.. _Installing-the-GNU-Taler-merchant-backend:
+
+Installing the GNU Taler merchant backend
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+backend
+The following steps assume all dependencies are installed.
+
+Use the following commands to download and install the merchant backend:
+
+::
+
+ $ git clone git://taler.net/merchant
+ $ cd merchant
+ $ ./bootstrap
+ $ ./configure [--prefix=PFX] \
+ [--with-gnunet=GNUNETPFX] \
+ [--with-exchange=EXCHANGEPFX]
+ $ # Each dependency can be fetched from non standard locations via
+ $ # the '--with-<LIBNAME>' option. See './configure --help'.
+ $ make
+ $ make install
+
+Note that you have to specify ``--with-exchange=/usr/local`` and/or
+``--with-exchange=/usr/local`` if you installed the exchange and/or
+GNUnet to ``/usr/local`` in the previous steps.
+
+.. _Installing-Taler-on-Debian-GNU_002fLinux:
+
+Installing Taler on Debian GNU/Linux
+------------------------------------
+
+Wheezy
+Debian
+Debian wheezy is too old and lacks most of the packages required.
+
+On Debian jessie, only GNU libmicrohttpd needs to be compiled from
+source. To install dependencies on Debian jesse, run the following
+commands:
+
+::
+
+ # apt-get install \
+ autoconf \
+ automake \
+ autopoint \
+ libtool \
+ libltdl-dev \
+ libunistring-dev \
+ libcurl4-gnutls-dev \
+ libgcrypt20-dev \
+ libjansson-dev \
+ libpq-dev \
+ postgresql-9.4
+ # wget https://ftp.gnu.org/gnu/libmicrohttpd/libmicrohttpd-latest.tar.gz
+ # wget https://ftp.gnu.org/gnu/libmicrohttpd/libmicrohttpd-latest.tar.gz.sig
+ # gpg -v libmicrohttpd-latest.tar.gz # Should show signed by 939E6BE1E29FC3CC
+ # tar xf libmicrohttpd-latest.tar.gz
+ # cd libmicrohttpd-0*
+ # ./configure
+ # make install
+
+For more recent versions of Debian, you should instead run:
+
+::
+
+ # apt-get install \
+ autoconf \
+ automake \
+ autopoint \
+ libtool \
+ libltdl-dev \
+ libunistring-dev \
+ libcurl4-gnutls-dev \
+ libgcrypt20-dev \
+ libjansson-dev \
+ libpq-dev \
+ postgresql-9.5 \
+ libmicrohttpd-dev
+
+For the rest of the installation, follow the generic installation
+instructions starting with the installation of libgnunetutil. Note that
+if you used the Debian wheezy instructions above, you need to pass
+``--with-microhttpd=/usr/local/`` to all ``configure`` invocations.
+
+How to configure the merchant’s backend
+=======================================
+
+taler-config
+taler.conf
+The installation already provides reasonable defaults for most of the
+configuration options. However, some must be provided, in particular the
+database account and bank account that the backend should use. By
+default, the file ``$HOME/.config/taler.conf`` is where the Web shop
+administrator specifies configuration values that augment or override
+the defaults. The format of the configuration file is the well-known INI
+file format. You can edit the file by hand, or use the ``taler-config``
+commands given as examples. For more information on ``taler-config``,
+see `Using taler-config <#Using-taler_002dconfig>`__.
+
+.. _Backend-options:
+
+Backend options
+---------------
+
+The following table describes the options that commonly need to be
+modified. Here, the notation ``[$section]/$option`` denotes the option
+``$option`` under the section ``[$section]`` in the configuration file.
+
+Service address
+ The following option sets the transport layer address used by the
+ merchant backend:
+
+ UNIX domain socket
+ TCP
+ ::
+
+ [MERCHANT]/SERVE = TCP | UNIX
+
+ If given,
+
+ - ``TCP``, then we need to set the TCP port in ``[MERCHANT]/PORT``
+
+ - ``UNIX``, then we need to set the unix domain socket path and mode
+ in ``[MERCHANT]/UNIXPATH`` and ``[MERCHANT]/UNIXPATH_MODE``. The
+ latter takes the usual permission mask given as a number, e.g. 660
+ for user/group read-write access.
+
+ The frontend can then connect to the backend over HTTP using the
+ specified address. If frontend and backend run within the same
+ operating system, the use of a UNIX domain socket is recommended to
+ avoid accidentally exposing the backend to the network.
+
+ port
+ To run the Taler backend on TCP port 8888, use:
+
+ ::
+
+ $ taler-config -s MERCHANT -o SERVE -V TCP
+ $ taler-config -s MERCHANT -o PORT -V 8888
+
+Currency
+ Which currency the Web shop deals in, i.e. “EUR” or “USD”, is
+ specified using the option
+
+ currency
+ KUDOS
+ ::
+
+ [TALER]/CURRENCY
+
+ For testing purposes, the currency MUST match “KUDOS” so that tests
+ will work with the Taler demonstration exchange at
+ https://exchange.demo.taler.net/:
+
+ ::
+
+ $ taler-config -s TALER -o CURRENCY -V KUDOS
+
+Database
+ DBMS
+ In principle is possible for the backend to support different DBMSs.
+ The option
+
+ ::
+
+ [MERCHANT]/DB
+
+ specifies which DBMS is to be used. However, currently only the value
+ "postgres" is supported. This is also the default.
+
+ In addition to selecting the DBMS software, the backend requires
+ DBMS-specific options to access the database.
+
+ For postgres, you need to provide:
+
+ ::
+
+ [merchantdb-postgres]/config
+
+ Postgres
+ This option specifies a postgres access path using the format
+ ``postgres:///$DBNAME``, where ``$DBNAME`` is the name of the
+ Postgres database you want to use. Suppose ``$USER`` is the name of
+ the user who will run the backend process. Then, you need to first
+ run
+
+ ::
+
+ $ sudu -u postgres createuser -d $USER
+
+ as the Postgres database administrator (usually ``postgres``) to
+ grant ``$USER`` the ability to create new databases. Next, you should
+ as ``$USER`` run:
+
+ ::
+
+ $ createdb $DBNAME
+
+ to create the backend’s database. Here, ``$DBNAME`` must match the
+ database name given in the configuration file.
+
+ To configure the Taler backend to use this database, run:
+
+ ::
+
+ $ taler-config -s MERCHANTDB-postgres -o CONFIG \
+ -V postgres:///$DBNAME
+
+Exchange
+ exchange
+ To add an exchange to the list of trusted payment service providers,
+ you create a section with a name that starts with “exchange-”. In
+ that section, the following options need to be configured:
+
+ - The “url” option specifies the exchange’s base URL. For example,
+ to use the Taler demonstrator use:
+
+ ::
+
+ $ taler-config -s EXCHANGE-demo -o URL \
+ -V https://exchange.demo.taler.net/
+
+ - master key
+ The “master_key” option specifies the exchange’s master public key
+ in base32 encoding. For the Taler demonstrator, use:
+
+ ::
+
+ $ taler-config -s EXCHANGE-demo -o master_key \
+ -V CQQZ9DY3MZ1ARMN5K1VKDETS04Y2QCKMMCFHZSWJWWVN82BTTH00
+
+ Note that multiple exchanges can be added to the system by using
+ different tokens in place of ``demo`` in the example above. Note
+ that all of the exchanges must use the same currency. If you need
+ to support multiple currencies, you need to configure a backend
+ per currency.
+
+Instances
+ instance
+ The backend allows the user to run multiple instances of shops with
+ distinct business entities against a single backend. Each instance
+ uses its own bank accounts and key for signing contracts. It is
+ mandatory to configure a "default" instance.
+
+ - The “KEYFILE” option specifies the file containing the instance’s
+ private signing key. For example, use:
+
+ ::
+
+ $ taler-config -s INSTANCE-default -o KEYFILE \
+ -V '${TALER_CONFIG_HOME}/merchant/instace/default.key'
+
+ - The “NAME” option specifies a human-readable name for the
+ instance. For example, use:
+
+ ::
+
+ $ taler-config -s INSTANCE-default -o NAME \
+ -V 'Kudos Inc.'
+
+ - The optional “TIP_EXCHANGE” and “TIP_EXCHANGE_PRIV_FILENAME”
+ options are discussed in Tipping visitors
+
+Accounts
+ wire format
+ In order to receive payments, the merchant backend needs to
+ communicate bank account details to the exchange. For this, the
+ configuration must include one or more sections named “ACCOUNT-name”
+ where ``name`` can be replaced by some human-readable word
+ identifying the account. For each section, the following options
+ should be provided:
+
+ - The “URL” option specifies a ``payto://``-URL for the account of
+ the merchant. For example, use:
+
+ ::
+
+ $ taler-config -s ACCOUNT-bank -o NAME \
+ -V 'payto://x-taler-bank/bank.demo.taler.net/4'
+
+ - The “WIRE_RESPONSE” option specifies where Taler should store the
+ (salted) JSON encoding of the wire account. The file given will be
+ created if it does not exist. For example, use:
+
+ ::
+
+ $ taler-config -s ACCOUNT-bank -o WIRE_RESPONSE \
+ -V '{$TALER_CONFIG_HOME}/merchant/bank.json'
+
+ - The “PLUGIN” option specifies which wire plugin should be used for
+ this account. The plugin must support the wire method used by the
+ URL. For example, use:
+
+ ::
+
+ $ taler-config -s ACCOUNT-bank -o PLUGIN \
+ -V taler_bank
+
+ - For each ``instance`` that should use this account, you should set
+ ``HONOR_instance`` and ``ACTIVE_instance`` to YES. The first
+ option will cause the instance to accept payments to the account
+ (for existing contracts), while the second will cause the backend
+ to include the account as a possible option for new contracts.
+
+ For example, use:
+
+ ::
+
+ $ taler-config -s ACCOUNT-bank -o HONOR_default \
+ -V YES
+ $ taler-config -s ACCOUNT-bank -o ACTIVE_default \
+ -V YES
+
+ to use “account-bank” for the “default” instance.
+
+ Depending on which PLUGIN you configured, you may additionally
+ specfiy authentication options to enable the plugin to use the
+ account.
+
+ For example, with ``taler_bank`` plugin, use:
+
+ ::
+
+ $ taler-config -s ACCOUNT-bank -o TALER_BANK_AUTH_METHOD \
+ -V basic
+ $ taler-config -s ACCOUNT-bank -o USERNAME \
+ -V user42
+ $ taler-config -s ACCOUNT-bank -o PASSWORD \
+ -V pass42
+
+ Note that additional instances can be specified using different
+ tokens in the section name instead of ``default``.
+
+.. _Sample-backend-configuration:
+
+Sample backend configuration
+----------------------------
+
+configuration
+The following is an example for a complete backend configuration:
+
+::
+
+ [TALER]
+ CURRENCY = KUDOS
+
+ [MERCHANT]
+ SERVE = TCP
+ PORT = 8888
+ DATABASE = postgres
+
+ [MERCHANTDB-postgres]
+ CONFIG = postgres:///donations
+
+ [INSTANCE-default]
+ KEYFILE = $DATADIR/key.priv
+ NAME = "Kudos Inc."
+
+ [ACCOUNT-bank]
+ URL = payto://x-taler-bank/bank.demo.taler.net/4
+ WIRE_RESPONSE = $DATADIR/bank.json
+ PLUGIN = taler_bank
+ HONOR_default = YES
+ ACTIVE_default = YES
+ TALER_BANK_AUTH_METHOD = basic
+ USERNAME = my_user
+ PASSWORD = 1234pass
+
+ [EXCHANGE-trusted]
+ URL = https://exchange.demo.taler.net/
+ MASTER_KEY = CQQZ9DY3MZ1ARMN5K1VKDETS04Y2QCKMMCFHZSWJWWVN82BTTH00
+ CURRENCY = KUDOS
+
+Given the above configuration, the backend will use a database named
+``donations`` within Postgres.
+
+The backend will deposit the coins it receives to the exchange at
+https://exchange.demo.taler.net/, which has the master key
+"CQQZ9DY3MZ1ARMN5K1VKDETS04Y2QCKMMCFHZSWJWWVN82BTTH00".
+
+Please note that ``doc/config.sh`` will walk you through all
+configuration steps, showing how to invoke ``taler-config`` for each of
+them.
+
+.. _Launching-the-backend:
+
+Launching the backend
+---------------------
+
+backend
+taler-merchant-httpd
+Assuming you have configured everything correctly, you can launch the
+merchant backend using:
+
+::
+
+ $ taler-merchant-httpd
+
+When launched for the first time, this command will print a message
+about generating your private key. If everything worked as expected, the
+command
+
+::
+
+ $ curl http://localhost:8888/
+
+should return the message
+
+::
+
+ Hello, I'm a merchant's Taler backend. This HTTP server is not for humans.
+
+Please note that your backend is right now likely globally reachable.
+Production systems should be configured to bind to a UNIX domain socket
+or properly restrict access to the port.
+
+.. _Testing:
+
+Testing
+=======
+
+The tool ``taler-merchant-generate-payments`` can be used to test the
+merchant backend installation. It implements all the payment’s steps in
+a programmatically way, relying on the backend you give it as input.
+Note that this tool gets installed along all the merchant backend’s
+binaries.
+
+This tool gets configured by a config file, that must have the following
+layout:
+
+::
+
+ [PAYMENTS-GENERATOR]
+
+ # The exchange used during the test: make sure the merchant backend
+ # being tested accpets this exchange.
+ # If the sysadmin wants, she can also install a local exchange
+ # and test against it.
+ EXCHANGE = https://exchange.demo.taler.net/
+
+ # This value must indicate some URL where the backend
+ # to be tested is listening; it doesn't have to be the
+ # "official" one, though.
+ MERCHANT = http://localbackend/
+
+ # This value is used when the tool tries to withdraw coins,
+ # and must match the bank used by the exchange. If the test is
+ # done against the exchange at https://exchange.demo.taler.net/,
+ # then this value can be "https://bank.demo.taler.net/".
+ BANK = https://bank.demo.taler.net/
+
+ # The merchant instance in charge of serving the payment.
+ # Make sure this instance has a bank account at the same bank
+ # indicated by the 'bank' option above.
+ INSTANCE = default
+
+ # The currency used during the test. Must match the one used
+ # by merchant backend and exchange.
+ CURRENCY = KUDOS
+
+Run the test in the following way:
+
+::
+
+ $ taler-merchant-generate-payments [-c config] [-e EURL] [-m MURL]
+
+The argument ``config`` given to ``-c`` points to the configuration file
+and is optional – ``~/.config/taler.conf`` will be checked by default.
+By default, the tool forks two processes: one for the merchant backend,
+and one for the exchange. The option ``-e`` (``-m``) avoids any exchange
+(merchant backend) fork, and just runs the generator against the
+exchange (merchant backend) running at ``EURL`` (``MURL``).
+
+Please NOTE that the generator contains *hardcoded* values, as for
+deposit fees of the coins it uses. In order to work against the used
+exchange, those values MUST match the ones used by the exchange.
+
+The following example shows how the generator "sets" a deposit fee of
+EUR:0.01 for the 5 EURO coin.
+
+::
+
+ // from <merchant_repository>/src/sample/generate_payments.c
+ { .oc = OC_PAY,
+ .label = "deposit-simple",
+ .expected_response_code = MHD_HTTP_OK,
+ .details.pay.contract_ref = "create-proposal-1",
+ .details.pay.coin_ref = "withdraw-coin-1",
+ .details.pay.amount_with_fee = concat_amount (currency, "5"),
+ .details.pay.amount_without_fee = concat_amount (currency, "4.99") },
+
+The logic calculates the deposit fee according to the subtraction:
+``amount_with_fee - amount_without_fee``.
+
+The following example shows a 5 EURO coin configuration - needed by the
+used exchange - which is compatible with the hardcoded example above.
+
+::
+
+ [COIN_eur_5]
+ value = EUR:5
+ duration_overlap = 5 minutes
+ duration_withdraw = 7 days
+ duration_spend = 2 years
+ duration_legal = 3 years
+ fee_withdraw = EUR:0.00
+ fee_deposit = EUR:0.01 # important bit
+ fee_refresh = EUR:0.00
+ fee_refund = EUR:0.00
+ rsa_keysize = 1024
+
+If the command terminates with no errors, then the merchant backend is
+correctly installed.
+
+After this operation is done, the merchant database will have some dummy
+data in it, so it may be convenient to clean all the tables; to this
+purpose, issue the following command:
+
+::
+
+ $ taler-merchant-dbinit -r
+
+
+Advanced topics
+===============
+
+Configuration format
+--------------------
+
+configuration
+In Taler realm, any component obeys to the same pattern to get
+configuration values. According to this pattern, once the component has
+been installed, the installation deploys default values in
+${prefix}/share/taler/config.d/, in .conf files. In order to override
+these defaults, the user can write a custom .conf file and either pass
+it to the component at execution time, or name it taler.conf and place
+it under $HOME/.config/.
+
+A config file is a text file containing sections, and each section
+contains its values. The right format follows:
+
+::
+
+ [section1]
+ value1 = string
+ value2 = 23
+
+ [section2]
+ value21 = string
+ value22 = /path22
+
+Throughout any configuration file, it is possible to use ``$``-prefixed
+variables, like ``$VAR``, especially when they represent filesystem
+paths. It is also possible to provide defaults values for those
+variables that are unset, by using the following syntax:
+``${VAR:-default}``. However, there are two ways a user can set
+``$``-prefixable variables:
+
+by defining them under a ``[paths]`` section, see example below,
+
+::
+
+ [paths]
+ TALER_DEPLOYMENT_SHARED = ${HOME}/shared-data
+ ..
+ [section-x]
+ path-x = ${TALER_DEPLOYMENT_SHARED}/x
+
+or by setting them in the environment:
+
+::
+
+ $ export VAR=/x
+
+The configuration loader will give precedence to variables set under
+``[path]``, though.
+
+The utility ``taler-config``, which gets installed along with the
+exchange, serves to get and set configuration values without directly
+editing the .conf. The option ``-f`` is particularly useful to resolve
+pathnames, when they use several levels of ``$``-expanded variables. See
+``taler-config --help``.
+
+Note that, in this stage of development, the file
+``$HOME/.config/taler.conf`` can contain sections for *all* the
+component. For example, both an exchange and a bank can read values from
+it.
+
+The repository ``git://taler.net/deployment`` contains examples of
+configuration file used in our demos. See under ``deployment/config``.
+
+ **Note**
+
+ Expectably, some components will not work just by using default
+ values, as their work is often interdependent. For example, a
+ merchant needs to know an exchange URL, or a database name.
+
+.. _Using-taler_002dconfig:
+
+Using taler-config
+------------------
+
+taler-config
+The tool ``taler-config`` can be used to extract or manipulate
+configuration values; however, the configuration use the well-known INI
+file format and can also be edited by hand.
+
+Run
+
+::
+
+ $ taler-config -s $SECTION
+
+to list all of the configuration values in section ``$SECTION``.
+
+Run
+
+::
+
+ $ taler-config -s $section -o $option
+
+to extract the respective configuration value for option ``$option`` in
+section ``$section``.
+
+Finally, to change a setting, run
+
+::
+
+ $ taler-config -s $section -o $option -V $value
+
+to set the respective configuration value to ``$value``. Note that you
+have to manually restart the Taler backend after you change the
+configuration to make the new configuration go into effect.
+
+Some default options will use $-variables, such as ``$DATADIR`` within
+their value. To expand the ``$DATADIR`` or other $-variables in the
+configuration, pass the ``-f`` option to ``taler-config``. For example,
+compare:
+
+::
+
+ $ taler-config -s ACCOUNT-bank \
+ -o WIRE_RESPONSE
+ $ taler-config -f -s ACCOUNT-bank \
+ -o WIRE_RESPONSE
+
+While the configuration file is typically located at
+``$HOME/.config/taler.conf``, an alternative location can be specified
+to ``taler-merchant-httpd`` and ``taler-config`` using the ``-c``
+option.
+
+.. _Merchant-key-management:
+
+Merchant key management
+-----------------------
+
+merchant key
+KEYFILE
+The option “KEYFILE” in the section “INSTANCE-default” specifies the
+path to the instance’s private key. You do not need to create a key
+manually, the backend will generate it automatically if it is missing.
+While generally unnecessary, it is possible to display the corresponding
+public key using the ``gnunet-ecc`` command-line tool:
+
+::
+
+ $ gnunet-ecc -p \
+ $(taler-config -f -s INSTANCE-default \
+ -o KEYFILE)
+
+.. _SEPA-configuration:
+
+Using the SEPA wire transfer method
+-----------------------------------
+
+SEPA
+EBICS
+The following is a sample configuration for the SEPA wire transfer
+method: [2]_.
+
+Then, to configure the EBICS backend for SEPA payments in EUR, the
+following configuration options need to be set:
+
+::
+
+ $ taler-config -s TALER -o CURRENCY -V EUR
+ $ taler-config -s ACCOUNT-e -o PLUGIN -V ebics
+ $ taler-config -s ACCOUNT-e -o URL \
+ -V payto://sepa/XY00111122223333444455556666
+ $ taler-config -s ACCOUNT-e -o WIRE_RESPONSE
+ -V '${DATADIR}/b.json'
+
+Please note that you will also have to configure an exchange and/or
+auditors that support SEPA. However, we cannot explain how to do this
+yet as such entities do not yet exist. Once such entities do exist, we
+expect future versions of the Taler backend to ship with pre-configured
+exchanges and auditors for common denominations.
+
+.. _Tipping-visitors:
+
+Tipping visitors
+----------------
+
+tipping
+Taler can also be used to tip Web site visitors. For example, you may be
+running an online survey, and you want to reward those people that have
+dutifully completed the survey. If they have installed a Taler wallet,
+you can provide them with a tip for their deeds. This section describes
+how to setup the Taler merchant backend for tipping.
+
+There are four basic steps that must happen to tip a visitor.
+
+.. _Configure-a-reserve-and-exchange-for-tipping:
+
+Configure a reserve and exchange for tipping
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+gnunet-ecc
+reserve key
+To tip users, you first need to create a reserve. A reserve is a pool of
+money held in escrow at the Taler exchange. This is the source of the
+funds for the tips. Tipping will fail (resulting in disappointed
+visitors) if you do not have enough funds in your reserve!
+
+First, we configure the backend. You need to enable tipping for each
+instance separately, or you can use an instance only for tipping. To
+configure the “default” instance for tipping, use the following
+configuration:
+
+::
+
+ [INSTANCE-default]
+ # this is NOT the tip.priv
+ KEYFILE = signing_key.priv
+ # replace the URL with the URL of the exchange you will use
+ TIP_EXCHANGE = https://exchange:443/
+ # here put the path to the file created with "gnunet-ecc -g1 tip.priv"
+ TIP_RESERVE_PRIV_FILENAME = tip.priv
+
+Note that the KEYFILE option should have already been present for the
+instance. It has nothing to do with the “tip.priv” file we created
+above, and you should probably use a different file here.
+
+Instead of manually editing the configuration, you could also run:
+
+::
+
+ $ taler-config -s INSTANCE-default \
+ -o TIP_RESERVE_PRIV_FILENAME \
+ -V tip.priv
+ $ taler-config -s INSTANCE-default \
+ -o TIP_EXCHANGE \
+ -V https://exchange:443/
+
+Next, to create the ``TIP_RESERVE_PRIV_FILENAME`` file, use:
+
+::
+
+ $ gnunet-ecc -g 1 \
+ $(taler-config -f -s INSTANCE-default \
+ -o TIP-RESERVE_PRIV_FILENAME)
+
+This will create a file with the private key that will be used to
+identify the reserve. You need to do this once for each instance that is
+configured to tip.
+
+Now you can (re)start the backend with the new configuration.
+
+.. _Fund-the-reserve:
+
+Fund the reserve
+~~~~~~~~~~~~~~~~
+
+reserve
+close
+To fund the reserve, you must first extract the public key from
+“tip.priv”:
+
+::
+
+ $ gnunet-ecc --print-public-key \
+ $(taler-config -f -s INSTANCE-default \
+ -o TIP-RESERVE_PRIV_FILENAME)
+
+In our example, the output for the public key is:
+
+::
+
+ QPE24X8PBX3BZ6E7GQ5VAVHV32FWTTCADR0TRQ183MSSJD2CHNEG
+
+You now need to make a wire transfer to the exchange’s bank account
+using the public key as the wire transfer subject. The exchange’s bank
+account details can be found in JSON format at
+“https://exchange:443//wire/METHOD” where METHOD is the respective wire
+method (i.e. “sepa”). Depending on the exchange’s operator, you may also
+be able to find the bank details in a human-readable format on the main
+page of the exchange.
+
+Make your wire transfer and (optionally) check at
+“https://exchange:443/reserve/status/reserve_pub=QPE24X...” whether your
+transfer has arrived at the exchange.
+
+Once the funds have arrived, you can start to use the reserve for
+tipping.
+
+Note that an exchange will typically close a reserve after four weeks,
+wiring all remaining funds back to the sender’s account. Thus, you
+should plan to wire funds corresponding to a campaign of about two weeks
+to the exchange initially. If your campaign runs longer, you should wire
+further funds to the reserve every other week to prevent it from
+expiring.
+
+.. _Authorize-a-tip:
+
+Authorize a tip
+~~~~~~~~~~~~~~~
+
+When your frontend has reached the point where a client is supposed to
+receive a tip, it needs to first authorize the tip. For this, the
+frontend must use the “/tip-authorize” API of the backend. To authorize
+a tip, the frontend has to provide the following information in the body
+of the POST request:
+
+- The amount of the tip
+
+- The justification (only used internally for the back-office)
+
+- The URL where the wallet should navigate next after the tip was
+ processed
+
+- The tip-pickup URL (see next section)
+
+In response to this request, the backend will return a tip token, an
+expiration time and the exchange URL. The expiration time will indicate
+how long the tip is valid (when the reserve expires). The tip token is
+an opaque string that contains all the information needed by the wallet
+to process the tip. The frontend must send this tip token to the browser
+in a special “402 Payment Required” response inside the ``X-Taler-Tip``
+header.
+
+The frontend should handle errors returned by the backend, such as
+missconfigured instances or a lack of remaining funds for tipping.
+
+.. _Picking-up-of-the-tip:
+
+Picking up of the tip
+~~~~~~~~~~~~~~~~~~~~~
+
+The wallet will POST a JSON object to the shop’s “/tip-pickup” handler.
+The frontend must then forward this request to the backend. The response
+generated by the backend can then be forwarded directly to the wallet.
+
+.. _Generate-payments:
+
+Generate payments
+-----------------
+
+testing database
+The merchant codebase offers the ``taler-merchant-benchmark`` tool to
+populate the database with fake payments. This tool is in charge of
+starting a merchant, exchange, and bank processes, and provide them all
+the input to accomplish payments. Note that each component will use its
+own configuration (as they would do in production).
+
+The tool takes all of the values it needs from the command line, with
+some of them being mandatory. Among those, we have:
+
+- ``--currency=K`` Use currency *K*, for example to craft coins to
+ withdraw.
+
+- ``--bank-url=URL`` Assume that the bank is serving under the base URL
+ *URL*. This option is only actually used by the tool to check if the
+ bank was well launched.
+
+- ``--merchant-url=URL`` Reach the merchant through *URL*, for
+ downloading contracts and sending payments.
+
+The tool then comes with two operation modes: *ordinary*, and *corner*.
+The first just executes normal payments, meaning that it uses the
+default instance and make sure that all payments get aggregated. The
+second gives the chance to leave some payments unaggregated, and also to
+use merchant instances other than the default (which is, actually, the
+one used by default by the tool).
+
+Note: the abilty of driving the aggregation policy is useful for testing
+the backoffice facility.
+
+Any subcommand is also equipped with the canonical ``--help`` option, so
+feel free to issue the following command in order to explore all the
+possibilities. For example:
+
+::
+
+ $ taler-merchant-benchmark corner --help
+
+will show all the options offered by the *corner* mode. Among the most
+interesting, there are:
+
+- ``--two-coins=TC`` This option instructs the tool to perform *TC*
+ many payments that use two coins, because normally only one coin is
+ spent per payment.
+
+- ``--unaggregated-number=UN`` This option instructs the tool to
+ perform *UN* (one coin) payments that will be left unaggregated.
+
+- ``--alt-instance=AI`` This option instructs the tool to perform
+ payments using the merchant instance *AI* (instead of the *default*
+ instance)
+
+As for the ``ordinary`` subcommand, it is worth explaining the following
+options:
+
+- ``--payments-number=PN`` Instructs the tool to perform *PN* payments.
+
+- ``--tracks-number=TN`` Instructs the tool to perform *TN* tracking
+ operations. Note that the **total** amount of operations will be two
+ times *TN*, since "one" tracking operation accounts for
+ ``/track/transaction`` and ``/track/transfer``. This command should
+ only be used to see if the operation ends without problems, as no
+ actual measurement of performance is provided (despite of the
+ ’benchmark’ work used in the tool’s name).
+
+.. [1]
+ https://docs.docker.com/
+
+.. [2]
+ Supporting SEPA is still work in progress; the backend will accept
+ this configuration, but the exchange will not work with SEPA today.