12.1. EBICS Implementation Notes

Warning

This document summarizes and clarifies some aspects of the EBICS protocol that are important to LibEuFin. Both version 3.0 and 2.5 are discussed here.

It is not a specification, and it does not replace the official EBICS specification.

12.1.1. EBICS Glossary

A004
Electronic signature process, used in H004, deprecated in H005 with EBICS 3.0.
A005
Electronic signature process. Used in H004 and H005.
A006
Electronic signature process. Used in H004 and H005.
BTF
Business Transaction Formats. Before EBICS 3.0, many different order types were used for business-related messages. With EBICS 3.0, the more generic BTU and BTD order types are used for all business-related messages.
E002
EBICS encryption process, used to encrypt the order payload.
EBICS
The Electronic Banking Internet Communication Standard.
EDS
Distributed Electronic Signature. Allows multiple subscribers to authorize an existing order.
ES

Electronic Signature. This abbreviation is commonly used in the context of EBICS.

The following signature classes are defined (in descending order from strongest to weakest):

E
Single signature (German “Einzeln”).
A
First signature.
B
Second signature.
T
Transport signature. Only used to verify authorized submission, but not to verify the bank-technical authorization.

In H004 and H005, the ES of the bank is specified as a “planned feature” that is not actually implemented yet. Thus banks in practice only use their encryption key pair and authentication/identity key pair.

FTAM
Historical predecessor protocol to EBICS (file transfer, access and management).
H004
Host protocol version 4. Refers to the XML Schema defined in EBICS 2.5.
H005
Host protocol version 5. Refers to the XML Schema defined in EBICS 3.0.
HEV
The Host EBICS Version. Queried by the client with an HEV request message.
Host ID
Alphanumeric identifier for the EBICS Host. One EBICS server can host multiple banks, and each bank is identified by the Host ID. This concept is similar to Taler’s merchant backend instance identifiers.
Human Subscriber
See Subscriber.
ISO 20022

ISO 20022: Financial Services - Universal financial industry message scheme. Rather important standard for financial industry business-related messages. In contrast, EBICS takes care of message transmission, segmentation, authentication, key management, etc.

The full catalogue of messages is available gratis.

Order Number

Interchangably called “Order ID”.

Each upload transaction gets a unique order number assigned by the bank server. The Order Number is used to match VEUs in a second upload to the original order. An Order Number matches the format [A-Z][A-Z0-9]{3} (and is not really a number!).

Must be unique per customer ID and per order type

Partner ID

In German, this is called “Kunden ID” (= Customer ID). One partner can have multiple “participants”, which are identified by user IDs.

Practical example: A company has one Partner ID. Each person at the company that can access the company’s bank accounts gets their own User ID. When the person is indirectly accessing the bank server (for example via a client server application), an additional “System ID” is created for this “technical subscriber”. When there is no technical subscriber, the System ID must be the same as the User ID. Usually the System ID is optional though.

The (partner, user, system) triple uniquely identifies a subscriber.

Segmentation

EBICS implements its own protocol-level segmentation of business-related messages. The segmentation can be seen as an alternative to the HTTP facilities of Accept-Ranges.

The order data of an ebics message may not exceed 1 MB. The segmentation applies both to requests and responses.

Subscriber

Entity that wishes to communicate with the financial institution via EBICS.

Subscribers can be technical or human. Technical subscribers are typically a server in client-server applications, where the server talks to a financial institution via EBICS.

Requests from technical subscribers have a SystemID in addition to a PartnerID and UserId. A technical subscriber cannot sign a bank-technical request.

System ID
See Partner ID.
Technical Subscriber
See Subscriber.
TLS
Transport Layer Security. All messages in EBICS are sent over HTTP with TLS. In the current version of the standard, only server certificates are required.
Transaction ID

A transaction ID is a 128-bit cryptographically strong random number. It is assigned by the bank server for every transaction, i.e. upload or download of an order.

The transaction ID must not be guessable, as it would allow a potential attacker to upload segments of an upload that do not match the whole message’s digest.

Transaction key
Symmetric encryption key for the data uploaded/downloaded in a transaction.
UNIFI
UNIversal Financial Industry message scheme. Sometimes used to refer to ISO 20022.
User ID
See Partner ID.
V001
FTAM encryption algorithm (“Verschlüsselung”), superseeded in EBICS by E002.
VEU
Distributed Electronic Signature (from German “Verteilte Elektronische Unterschrift”).
X002
Identification and authentication signature in H004 and H005.

12.1.2. Order Types

By convention, order types beginning with “H” are administrative order types, and other ones are bank-technical order types. This convention isn’t always followed consistently by EBICS.

Relevant Order Types

BTD
Only EBICS3.0+. Business Transaction Format Download. Administrative order type to download a file, described in more detail by the BTF structure
BTU
Only EBICS3.0+. Business Transaction Format Upload. Administrative order type to upload a file, described in more detail by the BTF structure
C52
Before EBICS 3.0. Download bank-to-customer account report (intra-day information).
C53
Before EBICS 3.0. Download bank-to-customer statement report (prior day bank statement).
CCC

Type: Upload.

Send SEPA Credit Transfer Initiation (pain.001) via XML container. This is the DFÜ variant (Appendix 3 DFÜ-Agreement)

CCT

Type: Upload.

Send SEPA Credit Transfer Initiation (pain.001) directly. This is the DFÜ variant (Appendix 3 DFÜ-Agreement)

CIZ

Type: Download.

Payment Status Report for Credit Transfer Instant.

CRZ

Type: Download.

Fetch payment status report (pain.002)

FDL
Before EBICS 3.0, France. File Download. Mainly used by France-style EBICS.
FUL
Before EBICS 3.0, France. File Upload. Mainly used by France-style EBICS.
HAA

Type: Download, Optional

Download order types for which there is new data available.

HAC
Customer acknowledgement. Allows downloading a detailed “log” of the activities done via EBICS, in the pain.002 XML format.
HCS
Change keys without having to send a new INI/HIA letter.
HCS
Change the subscribers keys (K_SIG, K_IA and K_ENC).
HIA
Transmission of the subscriber keys for (1) identification and authentication and (2) encryption within the framework of subscriber initialisation.
HKD

Type: Download, Optional

Download information about a customer (=partner). From German “Kundendaten”.

HPB
Query the three RSA keys of the financial institute.
HPD
Host Parameter Data. Used to query the capabilities of the financial institution.
HTD

Type: Download

Download information about a subscriber. From German “Teilnehmerdaten”.

INI
Transmission of the subscriber keys for bank-technical electronic signatures.
SPR
From German “sperren”. Suspend a subscriber. Used when a key compromise is suspected.

Other Order Types

The following order types are, for now, not relevant for LibEuFin:

AZV

Type: Upload.

From German “Auslandszahlungsverkehr”. Used to submit cross-border payments in a legacy format.

CCU

Type: Upload.

German “Eilüberweisung”.

CDZ

Type: Download.

Download payment status report for direct debit.

H3K

Type: Upload.

Send all three RSA key pairs for initialization at once, accompanied by a CA certificate for the keys. This is (as far as we know) used in France, but not used by any German banks. When initializing a subscriber with H3K, no INI and HIA letters are required.

HCA

Type: Upload.

Change the identification and authentication key as well as the encryption key (K_IA and K_ENC). Superseeded by HCS.

HSA

Type: Optional

Order to migrate from FTAM to EBICS. Removed in EBICS 3.0.

HVD

Type: Download.

Retrieve VEU state.

HVE

Type: Upload.

Host Verification of Electronic Signature. Used to submit an electronic signature separately from a previously uploaded order.

HVS

Type: Upload.

Cancel Previous Order (from German “Storno”). Used to submit an electronic signature separately from a previously uploaded order.

HVU

Type: Download.

Retrieve VEU overview.

HVU

Type: Download.

Retrieve VEU extra information. From German “Zusatzinformationen”.

PTK

Type: Download.

Download a human-readable protocol of operations done via EBICS. Mandatory for German banks. Superseeded by the machine-readable HAC order type.

PUB

Type: Upload.

Change of the bank-technical key (K_SIG). Superseeded by HSA.

12.1.3. EBICS Message Format

The following elements are the allowed root elements of EBICS request/response messages:

  • ebicsHEVRequest / ebicsHEVResponse: Always unauthenticated and unencrypted. Used only for query/response of the host’s EBICS version.
  • ebicsUnsecuredRequest: Request without signature or encryption (beyond TLS). Used for INI and HIA.
  • ebicsKeyManagementResponse: Unauthenticated response. Used for key management responses and sometimes also to deliver error messages that are not signed by the bank (such as “invalid request”).
  • ebicsNoPubKeyDigestsRequest: Signed request that does not contain the hash of the bank’s public key that the client expects. Used for key management, specifically only the HPB order type.
  • ebicsRequest / ebicsResponse
  • ebicsUnsignedRequest: Not used anymore. Was used in FTAM migration with the HSA order type.

12.1.4. Order ID Allocation

In practice, the Order ID seems to be allocated via number of counters at the level of the PartnerID.

12.1.5. EBICS Transaction

A transaction in EBICS simply refers to the process of uploading or downloading a file. Whether it is an upload or download transaction depends on the order type. Each transaction is either an upload transaction or a download transaction, neither both.

Uploads and downloads must proceed in segments of at most 1 MB. The segmentation happens after (1) encryption (2) zipping and (3) base64-encoding of the order data.

The number of segments is always fixed starting from the first message sent (for uploads) or received (for downloads) by the subscriber. The digest of the whole message is also sent/received with the first message of a transaction. The EBICS host generates a 128-bit transaction ID. This ID is used to correlate uploads/downloads of segments for the same transaction.

If an attacker would be able to guess the transaction ID, they could upload a bogus segment. This would only be detected after the whole file has been transmitted.

An upload transaction is finished when the subscriber has sent the last segment. A download transaction is only finished when the subscriber has sent an additional acknowledgement message to the EBICS host.

When upload/download of a segment fails, the client can always re-try. There are some conditions for that:

  • Segment n can only be downloaded/uploaded when segments [0..n-1] have been downloaded/uploaded.
  • The (implementation-defined) retry counter may not be exceeded.

12.1.6. Formats

ISO 20022

ISO 20022 is XML-based and defines message format for many finance-related activities.

ISO 20022 messages are identified by a message identifier in the following format:

<business area> . <message identifier> . <variant> . <version>

Some financial instututions (such as the Deutsche Kreditwirtschaft) may decided to use a subset of elements/attributes in a message, this is what the <variant> part is for. “Standard” ISO20022 have variant 001.

The most important message types for LibEuFin are:

camt - Cash Management
Particularly camt.053 (BankToCustomerStatement)
pain - Payment Initiation
Particularly pain.001 (CustomerCreditTransferInitiation) to initiate a payment and pain.002 (CustomerPaymentStatus) to get the status of a payment.

12.1.7. SWIFT Proprietary

SWIFT Proprietary messages are in a custom textual format. The relevant messages are MT940 and MT942

  • MT940 contains pre-advice, in the sense that transactions in it might still change or be reversed
  • MT942 contains the settled transactions by the end of the day

SWIFT will eventually transition from MT messages to ISO20022, but some banks might still only give us account statements in the old SWIFT format.

12.1.8. Key Management

RSA key pairs are used for three purposes:

  1. Authorization of requests by signing the order data. Called the bank-technical key pair, abbreviated here as K_SIG.
  2. Identification/authentication of the subscriber. Called the identification and authentication key pair, abbreviated here as K_IA.
  3. Decryption of the symmetric key used to decrypt the bank’s response. Called the encryption key pair, abbreviated here as K_ENC.

One subscriber may use three different key pairs for these purposes. The identification and authentication key pair may be the same as the encryption key pair. The bank-technical key pair may not be used for any other purpose.

12.1.9. Real-time Transactions

Real-time transactions will be supported with EBICS starting November 2019. That’s the earliest date, some banks may offer it later or not at all.

For us, CIZ is the relevant order type that we need to ask banks for.

12.1.10. Payment Reversal

It looks like there is no way to “reject” payments, unless you are the bank.

There is a concept of payment reversal (with pain.007 for direct debit and camt.055 for SEPA Credit Transfer), but they are a way for the payer / sender to reverse a payment before it is finalized.

12.1.11. Bank Support

All German banks that are part of the Deutsche Kreditwirtschaft must support EBICS.

The exact subset of EBICS order types must be agreed on contractually by the bank and customer. The following subsections list the message types that we know are supported by particular banks.

GLS Bank

According to publicly available forms, GLS Bank supports the following order types:

12.1.12. Cryptography

EBICS uses the XML Signature standard for signatures. It does not use XML encryption.

The EBICS specification doesn’t directly reference the standardized URIs for the various signing algorithms. Some of these URIs are defined in https://tools.ietf.org/html/rfc6931.

XML Signatures

XML Signatures can be a combination of:

  • detached (referencing another document)
  • enveloping (signs over Object tags within the Signature elements)
  • enveloped (signs over arbitrary data (via XPath expression) in other parts of the document that contains the signature).

In EBICS, only enveloped signatures are used.

In the XML Signature standard, the element for a signature is Signature. EBICS violates this standard by always mandating AuthSignature as the name. AuthSignature is an alias to the SignatureType xsd type in the XML Schema.

Canonicalization vs transforms:
  • Canonicalization refers to the processing of the SignedInfo element.
  • Transformations apply to the data that Reference elements reference. Canonicalization algorithms can be used as a transformation on referenced data.

12.1.13. Standards and Resources

EBICS

The EBICS standard documents are available at http://www.ebics.org.

EBICS 3.0:

  • The main EBICS 3.0 specification (2017-03-29-EBICS_V_3.0-FinalVersion.pdf).
  • Annex 1 specifies EBICS return codes, as EBICS doesn’t use HTTP status codes directly (2017-03-29-EBICS_V_3.0_Annex1_ReturnCodes-FinalVersion.pdf) .
  • Annex BTF contains the registry of BTF codes.

DFÜ Agreement

The DFÜ Agreement is the set of standards used by the German Banking Industry Committee (Deutsche Kreditwirtschaft).

The following Annexes (also see the DK Website) are relevant for implementing EBICS:

  • Annex 1 is the EBICS specification
  • (Annex 2 is deprecated)
  • Annex 3 describes the data formats used by German banks within EBICS.

EBICS Compendium

The EBICS Compendium has some additional info on EBICS. It is published by a company that sells a proprietary EBICS server implementation.