11.1. Nexus Manual

LibEuFin Nexus is an EBICS facilitator. It offers a command line interface to setup EBICS access, download banking records, and submit payments. Future versions will offer a Web API to allow Taler Exchanges to talk to their banks.

In this manual, we explain how to setup an EBICS subscriber. We assume that the bank had already granted EBICS access to the subscriber.

11.1.1. Installing Nexus

The following section was tested on an OpenJDK 17 environment. Building from source

Nexus belongs to the LibEuFin project, and can be downloaded via Git:

$ git clone git://git.taler.net/libeufin

Note that Kotlin and Gradle should already work on the host system.

Navigate into the libeufin local repository, and from top-level run:

$ ./bootstrap
$ ./configure --prefix=$PREFIX
$ make install-nexus

If the previous steps succeeded, the libeufin-nexus command should be found in the $PATH.

11.1.2. Setting up the EBICS subscriber

When you sign up for an EBICS-enabled bank account, the bank will provide you with various credentials. Those must be provided in the /etc/libeufin/libeufin-nexus.conf configuration file together with the name of the fiat currency.

The following snippet shows the mandatory configuration values:


# Bank
HOST_BASE_URL = http://bank.example.com/
BANK_DIALECT = postfinance

HOST_ID = mybank
USER_ID = myuser
PARTNER_ID = myorg

# Key files

# Account information
IBAN = myiban
BIC = mybic
NAME = myname


Refer to the manpage libeufin-nexus.conf(5) for the full array of configuration values.

Assuming that the configuration file exists at $config_file, the following command would start the EBICS setup process. The files CLIENT_PRIVATE_KEYS_FILE and BANK_PUBLIC_KEYS_FILE would be created at the CWD. Adjust their path to your setup (‘$HOME’ is currently not supported along paths).

libeufin-nexus ebics-setup -c $config_file

If the previous command succeeded, the subscriber keys reached the bank, but the setup should fail with an EBICS_INVALID_USER_STATE error code. That happens because the client tries to download the bank keys before having confirmed the subscriber keys via the traditional post service.

To that purpose, the previous run should have left a PDF document that the subscriber can print, sign, and send to the bank to confirm their subscriber keys. Look for the message looking like PDF file with keys hex encoding created at: /tmp/libeufin-nexus-keys-$timestamp.pdf.

Once the bank received and approved such printed document, run the same command again, in order to download the bank keys and let the user accept them.

libeufin-nexus ebics-setup -c $config_file

The setup is considered finished once the user accepts the bank keys.

11.1.3. Sending payments

Sending payments must follow a successful EBICS subscriber setup, where the bank obtained the subscriber keys, and the subscriber accepted the bank keys. The responsible subcommand for sending payments is ebics-submit, and its configuration is a superset of core-config. On top of that, it expects the database connection string, and optionally a frequency to check for submittable payments in the database.

The connection string is specified as


config = postgres:///nexus

The frequency may be specified as

frequency = 5m
# Optional, but useful to check what Nexus sends to the bank
submissions_log_directory = $LIBEUFIN_DATA_HOME/uploads

The supported time units are s (seconds), m (minutes), h (hours).

Before delving into the following sections, the database schema must be created, therefore run the following command:

libeufin-nexus dbinit -c $config_file

Where $config_file is the path to a configuration path that contains at least the [nexus-postgres] section. For testing

The ebics-submit subcommand is not suitable to send arbitrary payments, but rather to submit initiated payments that may be found in the database.

Such initiated payments may be refunds of incoming payments with a subject that would be invalid for a Taler withdrawal, or from a Taler exchange in the attempt to pay a merchant.

For testing purposes, however, it is possible to artificially initiate a payment into the database with the contrib/payment_initiation_debug.sh script, found in the libeufin repository. The script pays always one Swiss Franc to an IBAN and subject pair of choice.

The following invocation pays 1 CHF to the CH987654321 with an “Hello, Nexus!” subject.

./payment_initiation_debug.sh $config_file CH987654321 "Hello, Nexus!"

$config_file is the path to Nexus’ configuration file and it does not need the FREQUENCY value. If the previous command worked, now the database should contain a new row in the initiated_outgoing_transactions table, with an unsubmitted submission state.

The following command would now pick such an unsubmitted initiated payment and send it to the bank.

libeufin-nexus ebics-submit -c $config_file --transient

The --transient flag instructs the software to perform only one pass on the database, submit what is submittable, and return.

Alternatively, the --debug flag makes ebics-submit accept data from STDIN, and submit it to the bank. For production

The ebics-submit subcommand can run in fixed frequency, or transient mode.

The fixed frequency mode causes the command to check the database every time the frequency period expires. To activate this mode, and – for example – set a frequency of five minutes, set the configuration value FREQUENCY to 5m. Assuming that $config_fixed_frequency is set as described above, the following invocation would make ebics-submit check the database every five minutes, and submit any initiated payment according to their submission state.

libeufin-nexus ebics-submit -c $config_fixed_frequency

Transient mode causes ebics-submit to check the database only once, submit any initiated payment according to their submission state, and return.

libeufin-nexus ebics-submit -c $config

11.1.4. Downloading records

Downloading records must follow a successful EBICS subscriber setup, where the bank obtained the subscriber keys, and the subscriber accepted the bank keys.

The configuration file must contain all the [ebics-setup] sections, plus the following values to set the database connection and a log directory where any downloaded record would be stored.

config = postgres:///nexus
# Optional, but usfeful against data loss.
statement_log_directory = $LIBEUFIN_DATA_HOME/downloads

Assuming that $config_file contains any required option, the following command would download any unseen notifications (as camt.054 files).

libeufin-nexus ebics-fetch -c $config_file --transient

The --transient flag makes the command to download only once and return. If the bank returned any records, look in $LIBEUFIN_DATA_HOME/camt/YYYY-MM-DD to find them. YYYY-MM-DD is the date when the download took place.

To activate periodic downloads, add the following setting to the nexus-fetch configuration section in $config_file:

frequency = 5m

The following invocation would then download records every five minutes, asking the bank to only return documents that are timestamped from (inclusive) the last incoming transaction.

libeufin-nexus ebics-fetch -c $config_file Testing

If the bank account history has transactions that are useful for testing, it is possible to redownload them via the --pinned-start argument. Note: if the Nexus database contains already the bank account history, you might need to reset it, in order to have the redownloaded transactions ingested.


double-check the configuration: resetting the wrong database might cause DATA LOSS!

For example, say that three back on the 2023-06-01 an handful of incoming transactions got booked at the bank account watched by Nexus. After such day, the following command would redownload them (and ingest them, if the database doesn’t have them):

libeufin-nexus ebics-fetch -c $config_file --pinned-start 2023-06-01

Note: the command redownloads transactions from the pinned start until the present.