Encryption: the journey of a business secret

The economic cost of a backdoor · Part 2 of 7

An engineering drawing travels between colleagues, reaches another device and becomes part of a backup. At each stage, the keys determine who can read it and how the work can be recovered. An investigation into protection from the message to its surviving copies.

An engineering drawing can cross the internet without revealing its contents to intermediaries, then become accessible on a computer added to the conversation. Encryption can keep functioning as designed while the set of readers changes.

That distinction became particularly tangible in 2026. On 20 March, CERT-FR, France’s government incident-response service, published an alert about campaigns targeting instant messaging accounts, including those of people working in industry. The operations it described abused legitimate application features and users’ trust. On the same day, the US Federal Bureau of Investigation (FBI) and Cybersecurity and Infrastructure Security Agency (CISA) reported account takeovers that US authorities attributed to actors associated with Russian intelligence services. Their statement distinguished the compromise of accounts from a compromise of the applications’ encryption. ^T01T02

On 26 June, the two agencies described a further development: attackers were also seeking backup recovery keys, secrets used to help restore access to protected data, to gain access to older conversations. These events suggest a useful way to examine a messaging service: trace the message, the devices that can read it and the copies that extend its life. ^T03

To follow that journey, consider a fictional engineering consultancy. It exchanges prototype drawings, requested changes and commercial terms with a client. No actual incident or financial loss is attributed to this imaginary business. The example gives us an economic question to work through: where does confidentiality protect the work, and where can the reach of that protection change?

A secret needs to circulate

The design has value because it supports manufacturing, decisions and negotiations. Keeping it confidential matters for as long as premature disclosure could help a competitor or weaken a commercial discussion. Yet several people must be able to open it for it to be useful. The consultancy therefore needs to organise selective circulation: appropriate readers, an appropriate period of access and a way to retrieve the decisions made along the way.

Encryption transforms content into a form that requires a means of decryption to be usable. A key is a piece of data used by a cryptographic mechanism. The secret material needed to read the content must be protected. The practical question is who can use the keys, when, and for which copies. France’s data protection authority, the CNIL, distinguishes data in transit, in storage and being processed. Protection applied in one of these states describes only part of the journey. ^T08

Start with transport. TLS, the protocol used by HTTPS among other applications, protects a connection between its endpoints. When the consultancy sends a file to a service that terminates that connection, the service receives the stream carried inside it. If the file arrives without another layer of encryption, the service can process its readable contents. That arrangement enables functions such as previews, indexing and processing on the server. ^T04T08

End-to-end encryption adds another boundary. In the model below, content is encrypted on the sender’s device and decrypted on the recipient’s device. The relay carries content for which it does not hold the decryption keys. TLS can surround that exchange, protecting the connections to the servers as well. The two layers work together. The Messaging Layer Security (MLS) architecture published by the Internet Engineering Task Force (IETF) describes this relationship. It provides a messaging model, without claiming to represent every product’s implementation. ^T04T05

Method and scope

Simplified functional models, without a quantitative scale. The first assumes content delivered to the service without application-layer end-to-end encryption. The second retains TLS connections and adds content protection between authorised devices. Arrows describe functions rather than an actual packet trace. Keys, participant identity, device security, copies and metadata need separate assessment. RFC 9846 describes TLS 1.3; RFC 9750 describes a messaging architecture rather than every product.

For the consultancy, the economic benefit comes from reducing a dependency. In this model, the confidentiality of content in transit depends less on access controls at the relay. That reduces one category of exposure. Its effect on a potential loss then depends on the content, the other copies and what a third party could do with them. Turning a padlock icon into a financial saving would require information the protocol does not supply.

The question for the provider becomes specific: where does your service receive readable content? A documented answer allows a business to choose the functions it needs and accept the access those functions entail. The label “encrypted” leaves that decision unresolved.

One account can have several readers

On her screen, the engineer sees the name of the person she is speaking to. Within the system, devices and keys participate in the conversation. Connecting those two worlds correctly requires verification. Signal provides safety numbers for checking the cryptographic identity of a one-to-one exchange, with comparison over a trusted channel where the circumstances call for it. A change may have a legitimate explanation; it needs to be assessed in context. ^T07

That check answers a technical question. Professional authority raises a separate one: may the identified person receive the new design, accept the price or change the payment details? A properly protected channel can still carry an incorrect request from a known contact. In our example, confirming a sensitive change with the project lead belongs to the company’s internal procedures.

The number of readers can also change while the account name stays the same. A messaging service may allow several devices. Each becomes an endpoint able to receive certain content, depending on the service’s features. Signal’s current documentation distinguishes linking a device from choosing to transfer message history to it. MLS also treats adding a device and restoring earlier exchanges as separate mechanisms. Future messages and transferred archives therefore need to be examined separately. ^T24T05

Method and scope

A functional model of linked devices, without reproducing a lure or attack procedure. Device symbols aid explanation and measure neither victims nor a typical permitted-device count. A new device becomes a recipient after linking; its access depends on the service and settings. The history arrow is conditional on an available function and the choice made. March 2026 alerts describe abuse of legitimate functions rather than evidence of broken encryption. Verified cryptographic identity remains separate from professional authorisation.

The March 2026 alerts illustrate this distinction. The authorities describe deception that led victims to authorise an attacker-controlled device or let an attacker take over their account. The service could then deliver messages to an endpoint it regarded as authorised. CERT-FR states that the campaigns it describes did not rely on exploiting a vulnerability in the messaging application. That observation concerns those particular operations; it provides no general assurance about the application’s security. ^T01T02

For a business, useful work begins with an intelligible list of approved devices, a procedure for replacements and the removal of access that is no longer needed. The UK’s National Cyber Security Centre (NCSC) recommends reviewing linked devices and ensuring that messaging use follows workplace policies. The immediate purpose is practical: know which workstation can display the document. ^T21

Removing a device limits future access that depends on it, according to how the product works. A copy already exported has a life of its own. This asymmetry explains why control over recipients matters from the first transmission. Permission to read can result in a document the sender no longer controls.

A backup creates a second route

The project moves forward. An engineer changes her phone and wants to recover the client’s decisions. The need is legitimate: those exchanges may help keep the work going. Restoring them requires a usable copy and the means to read it. The backup file and its key become two objects to track.

The French cybersecurity agency ANSSI’s guide for small and medium-sized businesses puts the issue in practical terms: are backups encrypted, who holds the keys, and how are those keys backed up? The US National Institute of Standards and Technology (NIST) addresses the same decision through key management. Recovery helps an organisation resume work after a loss; how it is arranged depends on the keys’ functions and the application. ^T10T09

Apple’s documentation offers a particularly revealing example. Under standard data protection, when both Messages in iCloud and iCloud Backup are enabled, the backup contains a copy of the Messages key. Apple says this arrangement helps it recover messages for the user. Keys for the standard backup are held in its data centres. The recovery route described by the provider therefore includes an additional means of reaching the content. ^T11T12

With Advanced Data Protection, Apple describes a different arrangement. The backup and the Messages key it contains are end-to-end encrypted, with the means of decryption controlled by trusted devices. The setting changes how the means of reading the data are distributed. The diagram isolates this particular case; other iCloud categories and some metadata have their own protection arrangements. ^T11T12

Availability also depends on the account and country. Apple excludes Managed Apple Accounts, including those used by organisations, and child accounts. Its UK notice says users there who have not already enabled Advanced Data Protection can no longer turn it on. ^T13

Method and scope

The specific configuration described by Apple, with documentation checked on 7 November 2026. The drawing isolates two key roles: opening the backup and then using the copy of the Messages key inside it; it simplifies the complete cryptographic hierarchy. Under standard protection, Apple holds backup keys in its data centres. With Advanced Data Protection, decryption is controlled by trusted devices. Availability depends on country and account eligibility; managed Apple accounts and child accounts are excluded. In the UK, users who have not already enabled it can no longer enable it according to the reviewed notice. Some metadata and other iCloud categories have separate rules. This is the provider’s description, separate from an independent infrastructure audit.

This example provides a way to read service documentation. Follow the key that opens the messages, then the key that protects its copy, until the holder of each is identified. One layer of encryption can protect another while leaving the same operator with the means to follow the whole chain. A host can also store a file already encrypted by an application without holding its key.

WhatsApp illustrates the latter arrangement. Meta describes a backup encrypted by the application before it is stored with a cloud provider. WhatsApp’s documentation provides an option for end-to-end encrypted backups on iCloud or Google. Its activation and the selected recovery method need to be checked. The general protection of a cloud account therefore does not describe the protection of every application archive within it. These details come from supplier documents consulted for this investigation; they are not an independent audit of the implementation. ^T22T23

A recovery process designed for an individual’s convenience may require different arrangements within a business. Who keeps the means of restoration when someone moves to another role? Who may use it in their absence? How can the organisation prevent a single incident from taking both the archives and the only means of opening them? These questions belong in the assessment of business continuity, alongside the service’s other characteristics.

Captured traffic and retained history

An old exchange can survive as captured network traffic or as an application archive. The distinction explains a frequently misunderstood property: forward secrecy. In a protocol that provides it, discovering certain secrets later is insufficient to recover earlier session or message keys, under the protocol’s stated conditions. Those conditions include erasing the secrets needed to reconstruct the earlier keys. Guarantees vary with the modes used. ^T04T06

Signal’s Double Ratchet specification describes a mechanism that evolves secrets and derives successive message keys. The aim is to limit how far a compromise at one point in time can reach into the past. Actual operation includes intermediate states and the handling of delayed messages. These guarantees must be assessed under the protocol and each application’s design. ^T06

A person may nevertheless reopen an old conversation on their phone. The application has retained a history, with its own protection. The MLS architecture explicitly recognises that messages retained by an application may be readable after a device is compromised, without breaking the protocol that protected their transmission. Traffic intercepted yesterday and a copy available today provide two different routes to the content. ^T05

Backups introduce another architectural choice. In a publication dated 28 September 2026, Signal describes an additional key for its hosted backups, renewed daily within a trusted execution environment: a hardware-backed environment designed to isolate processing. This mechanism supplements the user’s recovery key. Signal specifies that its local backups, stored on a medium chosen by the user, follow a different model. Older copies of those backups may remain decryptable with the recovery key. These are properties described by the supplier. ^T15

The protection a backup provides depends on its architecture. To determine how far back an access route reaches, we need to know which copies remain available, which keys can be used and which additional protections apply. In the case described by the FBI and CISA in June, renewing the recovery key invalidates the old key for future backup downloads. The agencies note, however, that an attacker may already have downloaded a copy. ^T03

For the consultancy, that period matters. A comment that becomes routine after delivery and know-how that remains valuable for years call for different retention policies. Their value changes as the project progresses. Reducing the number of older copies may limit exposure; retaining certain decisions may be essential to the work or to meeting a legal obligation. That balance requires assessing the documents and then choosing where to keep them.

The content leaves traces around it

Protecting content leaves a separate question about the information needed to operate the service. Metadata describe characteristics or circumstances of an exchange, such as identifiers, timings or volumes, depending on the architecture. What is visible varies by actor. MLS addresses these matters separately from message secrecy and also recommends protection for the transport layer. ^T05

Apple specifies, for example, that some iCloud metadata remain under standard protection even when Advanced Data Protection is enabled. Its documentation includes information about synchronisation and modification. The value of such information to a third party depends on what that party can actually obtain and combine. In our fictional example, learning that a project has suddenly drawn in several teams might have commercial value. Establishing that would require evidence about the traces exposed and how they were used. ^T11

The workstation deserves the same examination. The CNIL recommends securing mobile computing, including encryption and locking, and assessing synchronisation mechanisms. Protecting a lost device and protecting an open session address different situations. Someone authorised to read the design may take a screenshot or export it; transport security does not govern that later use. ^T19

Disappearing messages address part of the retention problem. Signal explains that they remove messages from devices according to a timer, while warning that a recipient can keep an image of the content. The setting also needs to respect workplace archiving requirements. The NCSC makes this point in its guidance, and the EU’s General Data Protection Regulation (GDPR) links retention of personal data to its purposes, subject to the exceptions it provides. ^T16T21T17

The consultancy could distinguish a coordination conversation intended to disappear from a confirmed decision placed in a document repository with appropriate access rights. This is an organisational choice to adapt to the project. It allows retention to be discussed in terms of purpose, rather than keeping the entire history by habit.

Recovering the work while controlling the key

The strongest argument for easy recovery begins with an ordinary situation: the person who knows the project is absent, their device has been lost and the client is waiting for an answer. Continuity has value. A policy that makes a document permanently inaccessible may force work to be repeated or cause an interruption, even though confidentiality has held.

Restoration requires several conditions to be met: a usable copy that is recent enough, a means of decryption and the necessary access rights. The CNIL recommends checking backup integrity and testing restoration. NIST describes the backup and recovery of keys according to their functions. A file whose only secret has been lost may be perfectly preserved and unusable. ^T20T09

Services allocate this responsibility differently. Apple requires a recovery method to be prepared for Advanced Data Protection, such as a recovery contact or recovery key. A recovery contact helps restore access without automatically receiving access to the data. Signal states that restoring its secure backups requires the recovery key and that the service cannot reconstruct that key for the user. These choices should be assessed against the organisation’s actual needs. ^T13T14

A business may want to separate custody of the archives, custody of the recovery material and permission to use it. The practical arrangement depends on the service and the size of the team. The essential point is straightforward: an authorised person needs to be able to restore access when required, while a third party obtaining only a copy should not receive, through the same route, everything needed to read it. Such an arrangement requires procedures and tests. ANSSI’s guide provides a starting point for smaller organisations. ^T10

The economic cost starts here: choosing an architecture, configuring access, managing device changes and testing recovery. Those tasks may require staff time and outside services. Potential damage follows a separate chain. An incident has to expose data, and that access must then have a consequence for the business. The documentary record lets us describe these mechanisms. It provides neither a general probability of compromise nor a financial loss attributable to each one.

Encryption can also change the consequences of an incident involving personal data. Subject to conditions, Article 34 of the GDPR provides an exception to communicating a breach to the people affected where protective measures have effectively rendered the affected data unintelligible to unauthorised persons. The position of the keys therefore matters to the assessment. Duties to notify the supervisory authority under Article 33, and to document the breach, must be considered separately. ^T17

Choosing a service by tracing access to the document

A provider may describe its service through a broad promise. A business benefits from asking it to trace a real document: uploading, sharing, reading, adding a device, backing up, an employee leaving and restoration. At each stage, the answer should identify who could read the document and under what conditions. For cloud services, the CNIL recommends clarifying responsibilities and the provider’s assurances. Where it applies, the GDPR also governs relationships with processors. ^T25T17

At the consultancy, that description would help determine which exchanges should remain in a messaging service, where authoritative versions should be kept and how the client should receive access. It would also make visible a service the company requires: recovering its work. If that function introduces another holder of keys, the holder’s role belongs in the decision. If the recovery provider remains unable to read the content, the fallback procedure needs to work within that constraint.

French trade secret law provides another reason to document these choices. Article L. 151-1 of the Commercial Code requires, among other conditions, commercial value arising from the information’s secrecy and reasonable measures to preserve that secrecy. The information must also not be generally known or readily accessible to people familiar with that type of information. Encryption may form part of the protective measures; legal qualification depends on all the conditions being met. ^T18

This approach also provides a basis for examining backdoors. An additional access capability can be assessed by following the same journey: who receives a means of reading, which copies become accessible, over what period and under what governance? The answers determine the new dependencies and the work that needs funding. A targeted authorisation states a purpose; the technical reach is found in the architecture.

The consultancy needs to be able to trace its document throughout its life. A message protected on the network, a copy on a computer, a recoverable archive and a key kept elsewhere are different objects. How they fit together determines what a business can keep confidential, share and retrieve. Assessing access added to the system starts with that map.

Reading guide

End-to-end. Protection of content between the endpoints authorised by the system. Their identity and number need to be examined.

Recovery key. A secret that enables access to certain data to be restored, depending on the service’s architecture. Its scope needs to be established.

Forward secrecy. Conditional protection of the cryptographic past when a secret is compromised later. Retained message histories have their own protection.

Metadata. Information about objects or their exchanges. Collection and visibility depend on the service.

Restoration. Re-establishing usable access from a backup and the means needed to read it.

Method and limitations

This documentary investigation is current to 7 November 2026. It draws on public alerts, technical standards, legislation and official product documentation. Attribution of attacks is that of the authorities cited. Commercial architectures are described according to their suppliers, without penetration testing or an independent audit conducted for this article. Product characteristics may change.

The figures show mechanisms and the conditions under which they operate. They measure neither victim numbers, probabilities nor costs. The consultancy is fictional. Links and precise locators are provided in the references; the investigation distinguishes documented facts, inferences about mechanisms and the limits of each source.

Further reading

The sixth part on alternative routes to evidence examines available sources, investigative resources and the work of establishing evidence.

The fifth part on hijacked access and damage distinguishes affected capabilities, recovery and the distribution of losses.

The fourth part on iCloud, borders and switching costs examines safeguards, contracts and migration planning.

The third part on state access to messages examines authorisation, technical capabilities, oversight and the allocation of costs.

The first part on Parliament’s proposed encryption safeguard examines the powers under debate and the risks of additional access. The investigation into America’s secrets and post-quantum migration follows a separate undertaking: changing the cryptographic mechanisms themselves.

The sharing image illustrates copies of an engineering drawing moving between devices and an archive. The conceptual composition depicts neither an exact product nor an observed incident.

Sources

1. T01 · ANSSI / CERT-FR · 2026-03-20 · Accessed 7 November 2026Note d’alerte : Ciblage des messageries instantanées, CERTFR-2026-ALE-003
   Passages and scope

   CERTFR-2026-ALE-003, first issued 20 March 2026 and updated 18 June. Describes observed abuse of legitimate messaging-account functions, including targeting industrial staff. The observations are campaign-specific and separate from a general product or device-security audit.

2. T02 · FBI and CISA / Internet Crime Complaint Center · 2026-03-20 · Accessed 7 November 2026Russian Intelligence Services Target Commercial Messaging Application Accounts : I-032026-PSA
   Passages and scope

   IC3 I-032026-PSA, 20 March 2026, complete announcement. FBI and CISA attribute the campaign to Russian-intelligence-associated actors. Compromised accounts, linked devices and account takeover are distinct from broken application encryption. The reported global scale is separate from a French victim count.

3. T03 · FBI and CISA / Internet Crime Complaint Center · 2026-06-26 · Accessed 7 November 2026Russian Intelligence Services Continue to Target Commercial Messaging Applications : I-062626-PSA
   Passages and scope

   IC3 I-062626-PSA, 26 June 2026, complete update. Describes recovery-key targeting and invalidation of an old key for future backup downloads, while preserving the possibility of copies already downloaded. This dated observation predates the supplier’s September changes.

4. T04 · IETF / RFC Editor ; Eric Rescorla · 2026-07-11 · Accessed 7 November 2026RFC 9846 : The Transport Layer Security (TLS) Protocol Version 1.3
   Passages and scope

   RFC 9846, July 2026, Proposed Standard; official IETF history records publication on 11 July. Obsoletes RFC 8446. Connection endpoints, application encryption and mode-dependent forward-secrecy limits are distinct. Appendix F.1.5 excludes a general TLS post-compromise-security guarantee. A protocol specification, separate from a deployment audit.

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5. T05 · IETF / RFC Editor ; Beurdouche et al. · 2025-04 · Accessed 7 November 2026RFC 9750 : The Messaging Layer Security (MLS) Architecture
   Passages and scope

   RFC 9750, April 2025, Informational MLS architecture. Sections 6.7, 8.1 and 8.3.4 distinguish added clients, application-provided history restoration, transport metadata and retained messages with their own at-rest protection. This architecture is separate from every messaging product’s implementation.

6. T06 · Signal ; Trevor Perrin, Moxie Marlinspike et Rolfe Schmidt · 2025-11-04 · Accessed 7 November 2026The Double Ratchet Algorithm : revision 4
   Passages and scope

   Double Ratchet revision 4, 4 November 2025. Sections 2.1–2.6 and 8.1–8.4 address key evolution, deletion, fresh entropy for recovery and skipped-message keys. Active device compromise and readable application history require separate treatment; key rotation alone supplies no universal recovery guarantee.

7. T07 · Signal Support · Accessed 7 November 2026What is a safety number and why do I see that it changed?
   Passages and scope

   Current documentation for one-to-one safety numbers, changes and independent comparison. The page distinguishes cryptographic checking from a person’s identity; professional authority is an additional organisational question. A phone change or reinstall can have a legitimate explanation.

8. T08 · CNIL · 2024-01-22 · Accessed 7 November 2026Les pratiques de chiffrement dans l’informatique en nuage (cloud) public
   Passages and scope

   Analysis of 22 January 2024: data in transit, at rest and in processing; server-side and client-side encryption, key custody, supplier access and functional trade-offs. General institutional mechanisms, separate from an independent 2026 vendor audit.

9. T09 · NIST ; Elaine Barker · 2020-05-04 · Accessed 7 November 2026Recommendation for Key Management: Part 1 : General, Revision 5 (NIST SP 800-57 Part 1 Rev. 5)
   Passages and scope

   SP 800-57 Part 1 Rev 5, final 4 May 2020. Printed pages 49–52 and 104–107; compromise, operational continuity, backup storage and key recovery, including tables 7–8. Which keying material needs backup depends on key type and application. General guidance, with no universal product guarantee or cost estimate.

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10. T10 · ANSSI, DGE and partners · Accessed 7 November 2026La cybersécurité pour les TPE/PME en 13 questions : version 2.5
    Passages and scope

    ANSSI-GP-086 version 2.5, November 2024, printed in the PDF footer. Question 2, printed page 7/physical page 9, covers encryption before backup, key custody and backup, and restoration tests. The 12 December date in the filename is distinct from the printed version date. No standard recovery cost or duration is supplied.

11. T11 · Apple Support · 2026-01-05 · Accessed 7 November 2026iCloud data security overview
    Passages and scope

    Overview published 5 January 2026. The table and notes 3 and 9 describe the named iCloud Backup/Messages configuration under standard protection and Advanced Data Protection. Some categories are already end-to-end encrypted; certain metadata and sharing functions have other rules. Vendor description, not an independent implementation audit.

12. T12 · Apple Platform Security · Accessed 7 November 2026iCloud Backup security
    Passages and scope

    Sections on iCloud Backup and Messages in iCloud. Standard backup-service key storage, a Messages-key copy in an enabled backup, and end-to-end protection under Advanced Data Protection. Disabling backup generates a new key for future Messages data; this does not establish deletion of earlier copies. Scope is limited to the stated configuration.

13. T13 · Apple Support · Accessed 7 November 2026Activer Advanced Data Protection et préparer un contact de récupération
    Passages and scope

    Setup and recovery-contact documentation: an alternative recovery method and compatible devices/account are required. A contact helps with recovery without gaining account access by holding that role. Managed Apple Accounts and child accounts are excluded from Advanced Data Protection. Apple’s UK notice says new users there cannot enable it; availability must be checked by country and account.

    Additional primary document

    Additional primary document

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    Additional primary document

14. T14 · Signal Support · Accessed 7 November 2026Signal Secure Backups
    Passages and scope

    Current documentation for hosted Secure Backups. Opt-in end-to-end encrypted archive, a 64-character recovery key not shared with Signal, defined archive scope and exclusions for some disappearing messages. Restoration requires the recovery key. This is separate from older local backup formats and from WhatsApp’s 64-digit option.

15. T15 · Signal Blog · 2026-09-28 · Accessed 7 November 2026Back to Backups: A Year in Review
    Passages and scope

    Technical announcement of 28 September 2026. Hosted backups add a supplemental daily rotating key in a trusted execution environment; it cannot decrypt without the user’s recovery key. On-device copies lack that hosted layer and older corresponding archives can remain decryptable. Vendor-described architecture, separate from the June campaign and from evidence that previously obtained copies were erased.

16. T16 · Signal Support · Accessed 7 November 2026Set and manage disappearing messages
    Passages and scope

    Current disappearing-message documentation. Settings apply to new messages and sync across linked devices; timer behaviour depends on sending or receiving. Signal warns that recipients can preserve an image of a message. App-level expiry is separate from deletion of external photographs, exports or copies and from workplace retention obligations.

17. T17 · European Parliament and Council / EUR-Lex · 2016-05-04 · Accessed 7 November 2026Règlement (UE) 2016/679 : règlement général sur la protection des données
    Passages and scope

    GDPR, adopted 27 April 2016 and published 4 May. Articles 5(1)(e), 28, 32, 33 and 34: retention, processors, risk-appropriate security, restoration and breach response. Article 34 communication and Article 33 authority notification/documentation require separate assessment. Personal-data scope; no automatic product-level legal exemption.

18. T18 · Légifrance · Accessed 7 November 2026Code de commerce : article L. 151-1
    Passages and scope

    Commercial Code Article L. 151-1, current since 1 August 2018. Three cumulative business-secret conditions: limited accessibility, commercial value from secrecy and reasonable protective measures. An industrial drawing or confidentiality label alone establishes neither qualification nor its loss after an incident.

19. T19 · CNIL · 2024-03-14 · Accessed 7 November 2026Sécurité : Sécuriser l’informatique mobile
    Passages and scope

    Guidance of 14 March 2024: encryption and locking of mobile devices, personal equipment and scrutiny of backup/synchronisation terms. Storage protection, session security and backup protection address distinct situations. No product effectiveness measure is established.

20. T20 · CNIL · 2024-03-14 · Accessed 7 November 2026Sécurité : Sauvegarder
    Passages and scope

    Guidance of 14 March 2024: separate-site and offline copies, external-transfer encryption, integrity checks and restoration tests. Confidentiality, integrity and availability require complementary measures. Recommendations are separate from an identical legal duty, recovery time or cost for every organisation.

21. T21 · National Cyber Security Centre, United Kingdom · 2026-03-31 · Accessed 7 November 2026NCSC warns of messaging app targeting
    Passages and scope

    Warning of 31 March 2026, with an additional resource on 14 July. Recommends corporate services/devices where available, reviewing linked devices and participants, and respecting work-related retention requirements. Statements about exposed targets remain attributed and separate from average-user risk estimates.

22. T22 · Engineering at Meta · 2021-09-10 · Accessed 7 November 2026How WhatsApp is enabling end-to-end encrypted backups ; How Meta Is Strengthening End-to-End Encrypted Backups
    Passages and scope

    Technical descriptions of 10 September 2021 and 1 May 2026. Optional application-level backup encryption and HSM-based key-vault variants, separate from the cloud provider’s storage encryption. The 2026 over-the-air fleet-key distribution change is specifically for Messenger, while WhatsApp hardcodes fleet keys. These descriptions are attributed to the designer, not independently audited here.

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23. T23 · WhatsApp Help Center · Accessed 7 November 2026About end-to-end encrypted backup : versions iPhone et Android
    Passages and scope

    Current iPhone and Android help pages. iCloud/Google end-to-end backup encryption is an option to enable; WhatsApp cloud storage is described as always end-to-end encrypted but still in testing and potentially unavailable. Recovery can use a passkey, password or 64-digit key, subject to the device and service conditions. Usage/technical information may still be collected.

    Additional primary document

    Additional primary document

24. T24 · Signal Support · Accessed 7 November 2026Linked Devices
    Passages and scope

    Current linked-device documentation. Adding an endpoint and transferring message history are separate choices; access to content depends on product features and transfer settings. The page also describes review and unlink controls. A legitimate linked device is distinct from one authorised through deception, and unlinking does not establish erasure of copies already exported.

25. T25 · CNIL · 2024-03-14 · Accessed 7 November 2026Sécurité : Cloud, informatique en nuage
    Passages and scope

    Guidance of 14 March 2024: map cloud data and processing, assess suppliers, configure permissions and formalise responsibilities. The allocation of legal roles follows the actual processing; contracts or certification alone establish neither complete compliance nor secure configuration.