New EU legislation on identity wallets will also impact cryptography in Europe - a primer on Accepted Cryptographic Mechanisms

The authors of this blog are participating in the EU-funded project POSEIDON, which aims to provide smooth and reliable transition to post-quantum cryptography in digital identity management. 

Introduction 

European Digital Identity Wallets (EUDIW), regulated by the European Union Regulation eIDAS 2.0, will enable users to access online services, store and share digital documents and create binding signatures. The European Commission (hereinafter “the Commission”) has already released many Implementing Regulations concerning technical requirements for those wallets. 

Article 5a(23) of eIDAS 2.0 required the Commission to establish a list of reference standards – essentially laying out how it expects these wallets to function. The Commission thus far adopted four implementing acts, namely 

i. one laying down the relevant requirements for the integrity and core functionalities of EUDIW;

 ii. one dealing with protocols and interfaces;

iii. one about person identification data (PID) and electronic attestation of attributes (EAAs); and 

iv. one about notifications to the Commission. 

While still relatively recent, these four Implementing Regulations are nonetheless set to be amended, including with respect to the integrity and core functionalities of the EUDIW. 

As the technical specifications set out in eIDAS 2.0 rely on the work carried out on the basis of Commission Recommendation 2021/946 of 3 June 2021 on a common Union Toolbox for a coordinated approach towards a European digital framework and the Architecture and Reference Framework (ARF), the Commission should indeed amend this implementing Regulation to keep in line with the ARF, global developments and best practices on the internal market. 

In the section below, we’ll briefly explain the main changes, and notably how they will impact the use of cryptography by these wallets.

Changes concerning cryptography and accepted cryptographic mechanisms 

The Implementing Regulation (EU) 2024/2979 governing the integrity and core functionalities of European Digital Identity Wallets regulates certain technical requirements for EUDIW, such as: 

• their cryptographic security; 
• interoperability requirements; 
• authenticity and validity;
• revocation of wallet unit attestations; 
• formats for PID and EAAs; 
• how to implement selective disclosure; 
• qualified certificate; 
• signature creation applications; 
• data export, portability and data back-up; and 
• pseudonyms. 

In the original version of the Implementing Regulation, Article 4 required that wallet instances – i.e. the EUDIW app on the user’s phone - use at least one wallet secure cryptographic device to manage critical assets. In simple terms: the app has to interact with secure cryptographic hardware that ensures that its cryptographic functions are safe and trustworthy. However, the original Regulation did not specify which cryptographic mechanisms had to be used. 

This has changed with the amended version of the Implementing Regulation: Implementing Regulation (EU) 2026/1731 of 15 July 2026, available here. 

An new article, article 5a is inserted in Implementing Regulation (EU) 2024/2979: 

“Article 5a Cryptographic mechanisms 

Wallet providers shall, for the purposes of paragraph 2 of Article 4, use only the cryptographic mechanisms referred to in Annex Ia.” 

Article 4, paragraph 2 obliges wallet providers to ensure integrity, authenticity and confidentiality of the communication between wallet instances and wallet secure cryptographic applications. 

As a result, wallet providers can no longer freely choose which cryptographic mechanisms to use. Unlike the original version of the Implementing Regulation, it is from this point onwards mandatory to rely on the cryptographic mechanisms listed in Annex Ia. 

That enigmatic Annex Ia is very short and refers only to the cryptographic mechanisms specified by the European Cybersecurity Certification Group (ECCG), Sub-group on Cryptography, in the document entitled ‘Agreed Cryptographic Mechanisms’ (commonly referred to as ‘the crypto paper’). That paper was adopted and published in May 2025 by the European Union Agency for Cybersecurity (ENISA). Since the original Implementing Regulation was adopted around half a year earlier, it is clear why the crypto paper could not be referenced from the start. The paper is available on the following page: EUCC Guidelines on Cryptography - European Union Cybersecurity Certification. 

In practice, this document was already used in the context of trust services as providing a presumption of compliance. With the amendment of the Implementing Regulation, there is a clear alignment between the cryptographic mechanisms applicable to trust service providers and those applicable to European Digital Identity Wallet instances. 

Which cryptographic mechanisms are accepted? 

The crypto paper was primarily addressed to developers and evaluators and was thus inherently a form of non-binding “soft law”: authoritative, but not obligatory. However, through its explicit reference in the amended Implementing Act 2024/2979, it has now acquired legal value. It does, however, not yet take post-quantum cryptography (PQC) mechanisms into account, even though such mechanisms are currently being actively researched and developed. 

The legal requirement may thus become outdated in the future. ENISA is therefore working on updating its document to reflect advances in post-quantum cryptography. 

There is already a third version of the Agreed Cryptographic Mechanisms available here. However, this version is still a draft open for public review. It introduces several agreed-upon asymmetric post-quantum cryptographic mechanisms. 

In this context, the POSEIDON project is doing research on post-quantum cryptography mechanisms. The results of this research could eventually be integrated into the list of accepted cryptographic mechanisms in the future. The Agreed cryptographic mechanisms of the version that is in force (the version of May 2025) are divided into two categories, based on their estimated robustness: 

(i) Recommended mechanisms, which offer a high level of security and are considered suitable for long-term use. 

(ii) Legacy mechanisms, which are

• deployed on a large scale;
•  currently offer a security level of at least 100 bits; 

• and are considered to provide acceptable short-term security. 

  However, those legacy mechanisms should be phased out as soon as possible. Some legacy mechanisms are accompanied by specific deadlines in the crypto paper, which developers should carefully take into account. 

As the Amended Implementing Regulation refers to the ENISA crypto paper in its entirety, legacy mechanisms listed in the document are legally accepted under eIDAS for the technological functionality of the European Digital Identity Wallet. 

That said, it seems highly advisable to implement the recommended mechanisms wherever possible, in order to ensure long-term compliance and security, particularly in view of the anticipated finalisation of Version 3 in the near future. 

If you would like assistance with developing a European Digital Identity Wallet or understanding the legal and technical requirements under eIDAS 2.0 and Post-Quantum Cryptography, please do not hesitate to contact us.