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Nexus is a Web service that provides a JSON abstraction layer to access bank accounts. It is not itself a bank, but a translator between JSON requests and more structured banking protocols (like EBICS, for example.), that are offered by actual banks.
This document explains how to setup Nexus to access a bank account via the EBICS protocol. In order to follow all the steps below, the reader should already have one EBICS subscriber activated at their bank.
Nexus belongs to the LibEuFin project, and can be downloaded via Git:
$ git clone git://git.taler.net/libeufin
Note that Kotlin+Gradle should already work on the host system.
Navigate into the libeufin local repository, and from top-level run:
$ ./gradlew -Pprefix=$PREFIX nexus:installToPrefix $ ./gradlew -Pprefix=$PREFIX cli:installToPrefix
In case of success, the two following commands should be found:
$ which libeufin-nexus $ which libeufin-cli
Use the following command to (1) run the nexus service:
After the startup, Nexus should have created a
.sqlite3 file in
its current working directory. Feel free to use the
to change the database name and path. In future releases, the support
for Postgresql will be provided.
At this point a (2) superuser account needs to be activated into the system:
$ libeufin-nexus superuser foo # Will interactively ask for password
For simplicity, we’ll enable the superuser to access the bank account via the EBICS protocol, but a API to create less privileged users is as well offered.
Nexus needs now to associate the user to a EBICS subscriber that was activated on the bank. In the Nexus terminology, this is called (3) creating a EBICS connection.
The command line interface needs the following three values
to be defined into the environment:
NEXUS_PASSWORD. In this example, NEXUS_USERNAME should be
foo, and NEXUS_PASSWORD to the value given for its password
in step (2).
libeufin-cli \ connections \ new-ebics-connection \ --ebics-url $EBICS_BASE_URL \ --host-id $EBICS_HOST_ID \ --partner-id $EBICS_PARTNER_ID \ $CONNECTION_NAME
If the step above executed correctly, Nexus created all the cryptographic material that is needed on the client side; in this EBICS example, it created the signature and identification keys. It is therefore advisable to (4) make a backup copy of such keys.
libeufin-cli \ connections \ export-backup \ --passphrase $SECRET \ --outputfile $BACKUP_FILE \ $CONNECTION_NAME
At this point, Nexus must communicate all the details to the bank. Therefore, it will (5) synchronize the connection. In this EBICS example, Nexus will send the INI and HIA messages to the bank.
libeufin-cli \ connections \ sync \ $CONNECTION_NAME
Once the connection is synchronized, Nexus needs to import locally the data
corresponding to the bank accounts offered by the bank connection just made.
The command below (6) downloads the list of the bank accounts offered by the
libeufin-cli \ connections \ download-bank-accounts \ $CONNECTION_NAME
It is now possible to (7) list the accounts offered by the connection.
libeufin-cli \ connections \ list-offered-bank-accounts \ $CONNECTION_NAME
Nexus now needs an explicit (8) import of the accounts it needs to manage. This step is needed to let the user pick a custom name for such accounts.
libeufin-cli connections \ import-bank-account \ --offered-account-id $ACCOUNT_NATIVE_NAME \ --nexus-bank-account-id $CUSTOM_RENAMING_FOR_ACCOUNT \ $CONNECTION_NAME
Once a Nexus user imported a bank account (
under a certain connection (
$CONNECTION_NAME), it is possible
to accomplish the usual operations for any bank account: asking for the
list of transactions, and making a payment.
It is first needed to tell Nexus to download the latest news from the bank, and then ask it again to return the results.
This command asks Nexus to download the latest bank statements:
libeufin-cli \ accounts \ fetch-transactions \ $CUSTOM_RENAMING_FOR_ACCOUNT
Once Nexus stored all the information in the database, the client can ask to actually see the transactions:
libeufin-cli accounts \ transactions \ $CUSTOM_RENAMING_FOR_ACCOUNT
Payments pass through two phases: preparation and submission.
The following command prepares a payment:
libeufin-cli \ accounts \ prepare-payment \ --credit-iban $IBAN_TO_SEND_MONEY_TO \ --credit-bic $BIC_TO_SEND_MONEY_TO \ --credit-name $LEGAL_ENTITY_RECEIVING_THE_PAYMENT \ --payment-amount $AMOUNT \ --payment-subject $SUBJECT \ $CUSTOM_RENAMING_FOR_ACCOUNT
$AMOUNT value needs the format
X.Y:CURRENCY; for example
The previous command should return a value (
$UUID) that uniquely
identifies the prepared payment in the Nexus system. It’ll be needed
in the next step, to send the payment instructions to the bank:
libeufin-cli \ accounts \ submit-payment \ --payment-uuid $UUID \ $CUSTOM_RENAMING_FOR_ACCOUNT
The following command shows how to restore all the details associated with one bank connection subscription. For EBICS, this means that the INI and HIA secret keys will be restored for the requesting user.
libeufin-cli \ connection \ restore-backup \ --passphrase $SECRET \ --outputfile $BACKUP_FILE \ $CONNECTION_NAME
Facades are a additional abstraction layers that can serve specific purposes. For example, one application might need a filtered version of the transaction history, or it might want to refuse payments that do not conform to certain rules.
At this moment, only the Taler facade type is implemented in the Nexus, and the command below will show how to instantiate one under an existing bank account.
libeufin-cli \ taler-facade \ new-facade \ --facade-name $FACADE_NAME \ $CUSTOM_RENAMING_FOR_ACCOUNT \ $CONNECTION_NAME
At this point, the additional taler-wire-gateway (link here) API becomes offered by the Nexus. The purpose is to let a Taler exchange to rely on Nexus to manage its bank account.