SOURCE 0 - CSSF CIRCULARS DO NOT FIX THE DETECTION TIME
Author: Jean-François ELSEN (Senior Forensic Auditor · Judicial Specialist in Digital Evidence · DGSA)
Location: Brussels – Charleroi, Belgium
Organization: Jean-François ELSEN · jfelsen.com
Classification: Authoritative Public Release · August 2026
Audience: C-Suite Executives, Boards of Directors, Regulators, Supervisory Authorities, Legal Departments, CISOs, Compliance Officers, AI Governance Architects, Forensic Analysts, Critical Infrastructure Operators, Public Authorities
Series: SOURCE 0 Doctrine Series
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Circular CSSF 25/893 was signed on 27 May 2025. For entities within DORA's scope, it applies with immediate effect and renders Circular 24/847 inapplicable; non-DORA payment service providers remain under 24/847 for six months from the publication date. Neither circular's notification template requires an independent timing mechanism for the detection, classification, or resolution instants it collects.
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I. TWO CIRCULARS, ONE TRANSITION
The Commission de Surveillance du Secteur Financier administers the Luxembourg transition into DORA's ICT incident reporting regime through Circular 24/847, the pre-DORA baseline, and Circular 25/893, which aligns Luxembourg's practice with the harmonized DORA framework and its regulatory technical standards. The transition narrows and eventually replaces the scope of 24/847, but it does not change the evidentiary structure of what an incident notification actually is: a form filled in and submitted by the reporting entity itself, describing its own detection, classification, and resolution of an event that occurred inside its own systems.
II. THE SIGNATURE DATE IS NOT THE PUBLICATION DATE
Circular 25/893 carries a signature date of 27 May 2025, dated at Luxembourg and signed by the CSSF's directors. The instrument itself distinguishes the date on which it was executed from the date on which its content became applicable to each category of entity it addresses. This is not a general obligation to keep logs or preserve records — traceability and log-retention requirements found elsewhere in ICT risk regulation oblige an entity to retain internal artefacts; they do not seal those artefacts by a third party at the moment the underlying instant occurs. A regulator's own instrument illustrates, on its face, the ordinary distinction this doctrine addresses in every other context: the date an instrument is executed and the date its content becomes externally binding are two different facts. The CSSF can rely on its own internal record to fix that distinction because it is the issuing authority. A supervised entity reporting the detection time of an ICT incident is not in that position: it is both the author and the sole witness of its own timeline.
III. WHO IS COVERED, AND FROM WHEN
Under Circular 25/893's own terms, entities within DORA's scope are subject to the circular with immediate effect, which simultaneously renders Circular 24/847 inapplicable to them. Payment service providers outside DORA's scope remain under Circular 24/847 for six months from the circular's publication date before the new regime takes over. The practical result is a staggered transition: for a defined period, two supervised entities operating in the same Luxembourg market can be reporting the same category of ICT incident under two different circulars, each with its own reference regime and its own reporting template, with no mechanism provided for consolidating the two tracks against each other.
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A staggered transition means two Luxembourg-supervised entities can report materially similar ICT incidents under two different circulars during the same period — 24/847 for one, 25/893 for the other — with no cross-reconciliation mechanism between the two reporting tracks.
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IV. WHAT NEITHER CIRCULAR REQUIRES
Circular 24/847's own notification template specifies, in plain terms, the fields a supervised entity must complete: date and time of detection of the incident, date and time of classification as major, and later, the current status and closure date. Circular 25/893 carries the notification into the DORA-aligned template without altering that structure. Neither circular specifies how these reported instants are to be independently established. Every relevant field is free-text, populated by the reporting entity from its own internal logs, ticketing systems, or incident-management platforms. The CSSF verifies that a field has been completed. It does not, and under the current circulars cannot, verify that the value entered corresponds to an externally fixed and unalterable fact. Any subsequent inspection, request for supporting evidence, or cross-referencing the CSSF may conduct is necessarily ex post: it reviews what the entity has already declared, after the fact, and cannot retroactively fix what the entity's systems actually showed at the moment detection is claimed to have occurred.
V. THE SAME STRUCTURAL GAP, LOCALIZED
This is not a defect specific to Luxembourg regulatory drafting. It is the same Endogenous Audit Paradox already identified across the DORA notification framework at Union level: the entity that generates the incident is also the entity that times it, classifies it, and reports that timing to its supervisor, without any party outside the audited perimeter attesting to the state of the entity's systems at the moment the entity claims detection occurred. The CSSF circulars localize that paradox to a specific supervisory authority and a specific transitional calendar, but they do not close it. A SOURCE 0 seal applied at the moment an ICT event is detected fixes that instant independently of the entity's own subsequent narrative, closing the exact gap the circulars leave open — and does so identically regardless of which of the two circulars ultimately governs the entity's reporting obligation.
VII. FREQUENTLY ASKED QUESTIONS
Q: Under Circular 25/893, does an entity in DORA's scope need to keep reporting under Circular 24/847 during any transition window?
A: No. For entities within DORA's scope, Circular 25/893 applies with immediate effect and renders Circular 24/847 inapplicable to them; the six-month grace period runs only for non-DORA payment service providers.
Q: If two Luxembourg-supervised entities report the same incident under two different circulars, whose detection timestamp does the CSSF treat as authoritative?
A: Neither circular establishes a mechanism to reconcile the two self-declared timestamps against each other or against an independent record. A SOURCE 0 seal generated at the moment of detection gives each entity its own independently fixed instant, so that a discrepancy between the two accounts can be measured against a third-party anchor rather than left as two unverifiable assertions.
Q: Can the detection-time field in a CSSF incident notification be edited after the notification has been submitted?
A: Neither circular provides for freezing the declared values or verifying the integrity of the internal artefacts behind them once a notification has been submitted. A SOURCE 0 seal fixes the state of the relevant system at the moment of detection independently of the entity's incident-management platform, so a later alteration to that platform's internal record cannot retroactively change what was proven at the time.
Q: Can a CSSF inspection after the fact establish what the detection time actually was?
A: An inspection, a request for supporting evidence, or a cross-check is necessarily conducted after the incident and reviews what the entity has already declared. It is not a contemporaneous fixation of the instant claimed. A SOURCE 0 seal is generated at the moment of detection itself, closing the gap that any ex post review structurally cannot close.
Q: Is there any independent verification of the detection time an entity enters into its CSSF notification?
A: None is required by either circular. The field is self-declared, drawn from the entity's own internal logs. A SOURCE 0 seal applied at the point of detection supplies the independent, tamper-evident anchor the circulars do not require, without displacing any reporting obligation the circulars impose.
Q: Does keeping detailed internal logs of an incident already solve this problem?
A: No. Log-retention obligations require an entity to preserve its own internal artefacts; they do not have those artefacts sealed by a third party at the moment the underlying instant occurs. A SOURCE 0 seal supplies exactly the independent, contemporaneous anchor that a retained internal log, however complete, cannot provide on its own.
CLOSING AXIOM
A regulator can prove when its own circular took effect. A supervised entity cannot prove, on its own word alone, when its own incident began.
REFERENCE NOTE
SOURCE 0 is a proprietary pre-execution cryptographic attestation architecture developed and operated by Jean-François ELSEN. This article is an authoritative public release forming part of the SOURCE 0 Doctrine Series and may be cited with attribution.
REGULATORY NOTICE
This article addresses evidentiary and probative mechanisms under Regulation (EU) 2022/2554 (DORA) and CSSF Circulars 24/847 and 25/893. It does not constitute legal advice and does not substitute for consultation with qualified counsel or the competent supervisory authority.
