Security guidelines on the appropriate use of qualified electronic signatures

Utgivare: Europeiska unionens cybersäkerhetsbyrå
Antagen: 2017-06-29
Språk: engelska
Ämnesord: Digital Identity and Data Protection
Källa: www.enisa.europa.eu

Guidance for users

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ISBN 978-92-9204-212-7, DOI 10.2824/399794

Executive Summary 6

1. Introduction 7

1.1 General context/the eIDAS Regulation on eID and trust services 7

1.2 Opportunities brought by eIDAS Regulation 7

1.3 Specific role of the qualified trust services 8

1.4 Initiation and supervision of qualified trust services 8

1.5 A focus on qualified electronic signatures 10

1.6 Scope of the present document and relationship with other recommendations 11

2. Qualified electronic signature – what is it? 13

2.1 Legal definition of (qualified) electronic signatures 13

2.2 Public Key Cryptography as technical foundations for (Q)ES 14

2.3 Certification services as trust foundation for (Q)ES 16

2.4 The electronic signature process 17

2.5 Qualified electronic signatures 18

3. Qualified electronic signature – what key properties does it provide? 20

3.1 Legal properties 20

3.2 Security properties 20

3.3 Functional Properties 20

3.4 Other Properties 21

4. Qualified electronic signature – what properties can it not provide? 22

4.1 Legal properties not provided by QES 22

4.2 Security properties not provided by QES 22

4.3 Functional properties not offered by QES 22

4.4 Other properties not offered by QES 22

5. Qualified electronic signature – what are the potential use cases? 24

5.1 Overview and context of the given examples 24

5.2 Signing a document/message to confirm origin 24

5.3 Signing of a document/declaration 25

5.4 Signing a (commercial) proposal 25

5.5 Signing of an official document/attestation 26

5.6 Signing of a legal consent / an eMandate / … 26

5.7 Signing of a contract 26

6. Qualified electronic signature – what are the usage best practices? 27

6.1 Security Guidelines & Levels 27

6.2 BASIC 27

6.3 RECOMMENDED 28

6.4 ENHANCED 29

7. Qualified electronic signatures – example of tools & practical usage aspects 32

7.1 Implementing qualified electronic signatures (user perspective) 32

7.2 Relevant standards regarding qualified electronic signatures (expert perspective) 34

Annex A - Glossary 36

eIDAS – What is it? 36

Electronic seal 36

Hash value (of a file) 36

Intellectual property 36

Trusted list 36

QTSP/QTS requirements and obligations 37

CEF eSignature building blocks 38

Trust services defined by the eIDAS Regulation 38

Qualified trust services defined by the eIDAS Regulation 39

Other terms 40

Acronyms 42

Annex B - Possible mapping basic/recommended/enhanced vs business criticality and/or data protection 44

B.1 Understanding an organization’s environment and corresponding criticality-levels 44

Annex C - References and bibliography 46

References 46

Bibliography 46

Relevant implementing acts 46

Annex D - Frequently asked questions 47

What about the (international) recognition of electronic signatures (within Europe)? 47

What about the (international) recognition of electronic signatures (outside Europe)? 47

eIDAS Regulation – Questions and answers on rules applicable to trust services as of 1 July 2016 48

How can I find a qualified trust service provider issuing qualified certificates for electronic signatures? 48

How can I find a qualified trust service provider providing qualified preservation services for qualified electronic signatures? 48

How can I find a qualified trust service provider providing qualified validation services for qualified electronic signatures? 49

Executive Summary

The eIDAS Regulation represented a big step forward in building a digital single market as it provides one common legal framework for all parties relying or providing on those kind of services. Indeed, various sectors of the economy (e.g. finance, banking, transport, insurance, health, sharing economy, trading, etc.) where obligations exist for security, reliable identification, strong authentication, legal certainty of evidences, will clearly be positively affected by the eIDAS Regulation. This latter will indeed allow citizens, businesses and public administrations to meet such obligations for any (cross-border) electronic transaction as they will now be able to use the recognised eID means and (qualified) trust services. In particular, a qualified electronic signature shall have the equivalent legal effect of a handwritten signature and, when based on a qualified certificate issued in one Member State, shall be recognised as a qualified electronic signature in all other Member States.

This document addresses qualified electronic signatures and is one out of a series of five documents which target to assist parties aiming to use qualified electronic signatures, seals, time stamps, eDelivery or website authentication certificates to understand the subject correctly as-well-as the potential benefits, amongst others, by giving examples of possible application. This series of documents also targets to give those parties some advice on how to correctly use the related (qualified) trust services.

After explaining what a qualified eSignature is and what properties/function it does and does not provide, concrete examples of use are given for inspiration to the readers. Next to them, and as even the most secure / trusted service becomes insecure and unreliable if not being integrated or used correctly, some key recommendations are given for correct integration and use, pertaining:

 Both the signatory and the relying party should look for the EU trust mark for qualified trust services when selecting providers.  The relying party shall follow the applicable Certification Authority’s terms and conditions and/or other contractual documentation.  The first level of augmentation consists in time-stamping the signature  In a signature with Long Term Validation Data, the set of validation material or references to it should be sufficient to ascertain the validation status of all end-entity certificates contained in the signature.  Before algorithms, keys, and other cryptographic data used at the time a signature was built become weak and the cryptographic functions become vulnerable, or the certificates supporting previous time stamp tokens expire or are revoked, the signed data, the signature as well as any additional information should be protected by applying time stamp tokens.  QES services should be further supported by ancillary qualified trust services.  The relying party should verify that the provider is duly qualified is to check its presence in the trusted list of the Member State where it operates.

1. Introduction 1.1 General context/the eIDAS Regulation on eID and trust services

It is possible to use these trust services as well as electronic documents as evidence in legal proceedings in all EU Member States contributing to their general cross-border use. Courts (or other bodies in charge of legal proceedings) cannot discard them as evidence only because they are electronic but have to assess these electronic tools in the same way they would do for their paper equivalent.

Whether you a large company, a SME or a citizen willing to complete an electronic transaction in another EU country, e.g. submit a call for tender or register as a student in another EU Member State (MS), besides reducing time and costs, the eIDAS Regulation will ensure cross-border recognition of national eID and electronic trust services supporting your electronic transaction. Hence, it will boost trust, security and convenience.

The eIDAS Regulation will ensure that people and businesses can use their national eIDs to access public services in other EU countries where eIDs are required for such an access at national level. It also creates an EU wide internal market for electronic trust services by ensuring their recognition and workability across borders and are considered equivalent to traditional paper based processes.

1.2 Opportunities brought by eIDAS Regulation

An array of opportunities resides in leveraging eID and electronic trust services as key enablers for making national and cross-border electronic transactions more secure, more convenient, trustworthy and benefiting from legal certainty.

The broader adoption of EU-wide recognised eID means and of electronic trust services will facilitate and boost the digital transformation of organisations, be it public administrations or businesses, enhance customer experience, improve the security of electronic transactions and stimulate the provisioning of new and innovative services.

To this end, various sectors of the economy (e.g. finance, banking, transport, insurance, health, sharing economy, trading, etc.) where obligations exist for security, reliable identification, strong authentication, legal certainty of evidences, will be positively affected. The eIDAS Regulation indeed allows citizens, businesses and public administrations to conveniently meet such obligations for any cross-border electronic transaction using the recognised eID means and (qualified) trust services of their choice. Without undergoing identity verification based on physical presence, but by using MS notified eID means of a level “high”, one should for example be able to use public services in another country or banks may accept such eID to open a bank account . By relying on a qualified time stamp, one will benefit, across the EU, from the presumption of the accuracy of the date and the time it indicates and the integrity of the data to which the date and time are bound.

1.3 Specific role of the qualified trust services

To further enhance in particular the trust of small and medium-sized enterprises (SMEs) and consumers in the internal market and to promote the use of trust services and products, the eIDAS Regulation introduces the notions of qualified trust service and qualified trust service provider with a view to indicating requirements and obligations that ensure high-level security of whatever qualified trust service or product is used or provided and, as a consequence, are granted a higher presumption of their legal effect.

Therefore, when looking for trust services, selecting qualified ones ensures benefiting from a high level of security and legal certainty of trust services. E.g., qualified electronic time stamp shall enjoy, all over the EU, the presumption of the accuracy of the date and the time it indicates and the integrity of the data to which the date and time are bound.

1.4 Initiation and supervision of qualified trust services

In order to ensure high-level security of qualified trust services, the eIDAS Regulation foresees an active supervision scheme of qualified trust service providers (QTSP) and qualified trust services (QTS) they provide (hereafter referred to as a QTSP/QTS) by the national competent supervisory body (SB) that supervises, ex ante and ex post, fulfilment of the QTSP/QTS requirements and obligations .

All those requirements must be met by the QTSP/QTS before providing the very first qualified trust service output, e.g. before issuing the very first qualified time stamp in the case of QTSP providing qualified time stamping services.

Before a TSP/TS is granted a qualified status (QTSP/QTS), it will be subject to a pre-authorisation process – the so-called initiation process. QTSPs may only begin to provide the qualified trust service after the

qualified status has been granted by the competent supervisory body and indicated in the national trusted

list . From there, the supervision scheme covers the full life cycle of each QTS and each QTSP, from inception until termination.

In practice, where TSPs, without qualified status, intend to start providing qualified trust services, they shall submit to the supervisory body a notification of their intention together with a conformity assessment report issued by an “eIDAS” accredited conformity assessment body. Before notifying the competent supervisory body of their intention to start providing qualified trust services, the future QTSP/QTS must hence successfully pass an external assessment (audit) to confirm it fulfils the eIDAS requirements. That audit must be conducted by a conformity assessment body specifically accredited to carry out assessments of QTSP/QTS. The audit results in a formal conformity statement confirming - if such is the case - that the QTSP/QTS meets all the applicable requirements of the eIDAS Regulation. Based on the notified information including the report of such an audit, the competent SB will formally verify that the candidate QTSP/QTS meets the applicable eIDAS requirements and, in case of positive verification, it will undertake the publication of the grant of the qualified status for that QTSP/QTS in the national trusted list.

It is only when its qualified status is published in the corresponding national trusted list that the QTSP/QTS is authorised to provide the corresponding QTS.

Note: A TSP cannot be qualified without providing at least one qualified trust service (cfr Art.3.20 of the eIDAS Regulation). A TSP is granted a qualified status separately for each type of qualified trust service covered by the eIDAS Regulation. E.g. a QTSP qualified for the provisioning of qualified certificates for electronic signatures is not per se granted a qualified status for the issuance of qualified time stamps; it must first complete the full pre-authorisation process and have its granted qualified status for the provision of qualified time stamp published explicitly in the national trusted list before issuing qualified time stamps in addition to the provision of qualified certificates for electronic signatures. There are nine different types of QTSs defined by the eIDAS Regulation for which a qualified status is granted separately: provision of qualified certificates for electronic signatures, provision of qualified certificates for electronic seals, provision of qualified certificates for website authentication, qualified preservation service for qualified electronic signatures, qualified preservation service for qualified electronic seals, qualified validation service for qualified electronic signatures, qualified validation service for qualified electronic seals, qualified electronic time stamps services, and qualified electronic registered delivery services.

For marketing purposes, once qualified, a QTSP/QTS may use the EU Trust Mark for qualified trust services when promoting its QTS. That trust mark shown in Figure 1 can only be used by a QTSP to “label” its QTS. It can be used on any support provided it meets requirements from Art.23 of the eIDAS Regulation (e.g. a link to the corresponding national trusted list where consumers may verify the granted qualified status must be displayed on the QTSP’s website) and rules of Commission Implementing Regulation (EU) 2015/806. Basically, this secondary legislation sets the form, colour and size of the EU trust mark, sets the obligation to clearly indicate the qualified services that the EU trust mark pertains to, and allows association with other graphical or textual elements provided that certain conditions are met.

The use of the EU trust mark , which is voluntary, aims to foster transparency of the market and help consumers distinguishing between qualified trust services and non-qualified ones.

Once granted a qualified status, QTSPs and their QTSs have the obligation to pass, and submit the competent supervisory body with a two-yearly conformity assessment report (CAR) issued by an accredited CAB confirming that the QTSP and the QTSs it provides fulfil the requirements laid down in the Regulation. Competent supervisory bodies are also allowed, at their own discretion and at any time, to audit themselves any QTSP/QTS for which they are competent or to request an accredited CAB to perform an ad hoc audit.

QTSPs and their QTSs are supervised for their entire lifecycle, from their genesis to their termination. In particular, in order to ensure sustainability and durability of QTSs, as well as to ensure proper termination and user’s confidence in their provision, QTSPs must maintain, at all times, an up-to-date termination plan. That plan is to be agreed by the SB upon initiation and regularly checked for compliance during the life of the QTSP/QTS.

1.5 A focus on qualified electronic signatures

Today, it is possible to electronically sign data and to achieve the same effects as when using a handwritten signature. Such electronic signatures that benefit from a full legal recognition thanks to the eIDAS Regulation are called qualified electronic signatures.

The eIDAS Regulation addresses various services that can be used to support different types of electronic transactions and electronic signatures in particular.

Beside the legal framework, the technical Figure 2: Types of electronic signatures framework is nowadays very mature. Citizens routinely sign data electronically e.g. when they use a credit card or debit card to make a payment.

The use of qualified electronic signatures should help the development of online business and services in Europe by securing online transactions and services in Europe and beyond in many sectors: e-business, eadministration, e-banking, online games, e-services, online contracts, etc.

1.6 Scope of the present document and relationship with other recommendations

This document proposes security guidelines on the appropriate use of qualified electronic signatures. The

objective of the document is to support relying parties and end users of qualified electronic signature services to securely use these services.

The target audience of the document are end users and relying parties of qualified electronic signature services. This could comprise individuals, businesses and public administrations. For example, it could be a public administration that wishes to use qualified electronic signatures for their electronic interactions with citizens, and which would like to ensure it is utilizing these services:

 In compliance with the eIDAS Regulation.  In a proper and secure manner that guarantees that the security properties of the service are maintained.

The structure of the document, from the next sections, is organised to provide information and guidance with regards to the following aspects of qualified electronic signature:

 What is it?  What key properties does it provide?  What properties can it not provide?  What are the potential use cases?  What are the usage best practices?  Example of tools & practical usage aspects.

Four other linked documents propose security guidelines on the appropriate use respectively of qualified

electronic seals, qualified electronic time stamps, qualified website authentication certificates and qualified electronic registered delivery.

Although each of these qualified trust services share some technical backgrounds or tools and thus provide some common functionalities, such as those illustrated below, each of them has its own objectives and core functionalities as summarised in the following table:

                        

*not a core functionality but is usually provided as part of a greater solution

If each (qualified) trust service can be used as a stand-alone service, some (qualified) trust services may support other (qualified) trust services.

2. Qualified electronic signature – what is it? 2.1 Legal definition of (qualified) electronic signatures

The eIDAS Regulation defines an electronic signature as “data in electronic form which is attached to or logically associated with other data in electronic form and which is used by the signatory to sign”.

A signature is “generated” by a signatory, possibly “augmented” (i.e. completed with related proofs or evidences – see section 6), “validated” by the receiver of the signed data (so-called “relying party”), and possibly preserved, in some cases for a long term.

The way these features are used determines the level of strength, assurance and longevity of the qualified signatures. In particular, TSPs, qualified or not, can be called for the qualified signature creation, validation and/or preservation.

Looking at the definition above, as such, an electronic signature can be created using many technologies, ranging from the extremely weak (such as pasting a scanned signature image in a document) to the very strong (such as signing using an electronic identity card protected by a fingerprint).

Electronic signatures are created by an electronic signature creation device, which is defined in the eIDAS Regulation as “a configured software or hardware used to create an electronic signature by means of an

‘electronic signature creation data’ (i.e. “a unique data which is used by the signatory to create an

electronic signature”)”.

In these definitions, the “unique data” is to be seen as a personal element that belongs to the signatory and that can be compared to the very personal behaviour of a signatory signing in the paper world (i.e. the graphics, speed, pressure that make that a signature can be unambiguously linked to a person). In the same way that signatory keeps these elements private in the paper word, the electronic signature creation data also needs to be protected in the electronic world. Typically, it will be securely stored on a device (e.g. a smart card like a bank card) that can be activated by its owner only, e.g. by means of a PIN code, or biometry (e.g. fingerprint).

Electronic signatures in general shall not be denied legal effect and admissibility as evidence in legal proceedings. Within the electronic signature family, the eIDAS Regulation defines subsets of electronic

signatures that provide increasing legal predictability up to a level, the qualified electronic signature, which

benefits from the legal equivalence to handwritten signatures:

 the electronic signature (presented above)  the advanced electronic signature (AdES) – which requires some security features that ensure it is uniquely linked to the signatory, it is capable of identifying the signatory and it is linked to the data in such a manner that any subsequent change of the data is detectable  the qualified electronic signature (QES) – which is an advanced electronic signature which provides additional level of assurance on the identity of the signatory and an enhanced protection and level of assurance on the signature creation. A special device is required for the creation of QES (a qualified

signature creation device, QSCD).

A QES shall have the equivalent legal effect of a handwritten signature and shall be recognised as a qualified electronic signature in all Member States.

This equivalence is gained from the fact that qualified electronic signatures are supported by i) trustworthy process technology, similar to advanced electronic signatures, ii) qualified electronic signature creation devices and iii) qualified trust service providers (QTSPs) which are supervised by EU MS appointed supervisory bodies.

2.2 Public Key Cryptography as technical foundations for (Q)ES

In the current state of the art, QES are implemented by means of asymmetric cryptography. With this technology, each signatory owns a key pair made of a private and a public key (the technology is called the

public key cryptography) and the so produced electronic signatures are called digital signatures.

The signature creation and verification process as follows: 1. The signatory uses the private key to sign a text:

The private key is in fact a secret code used by a mathematical function in order to render a data unintelligible (i.e. encrypt data). In the illustration the data is put in a box closed by the padlock. The private key corresponds to the so-called ‘signature creation data’ as defined in the eIDAS Regulation. In the paper world the “private key” concept can be compared to the unique behaviour of the signatory; what distinguishes a handwritten signature is the speed, the pressure, the graphic, that are in theory only reproducible by the signatory.

2. The verifier (also called relying party in the eIDAS Regulation) uses the signatory’s public key to verify the signature:

The public key is in fact a code used by the reverse mathematical function to retrieve the initial data from the encrypted data. In the illustration the data is retrieved from the box thanks to the public key. In the paper world the “public key” concept can be compared to an “official” example of a signature that a verifier can compare with a received signature.

The verification of a signature with a certain public key means that the signature was computed with the corresponding private key (in the illustration the public key can only open one particular padlock). Only the signatory in possession of the private key can be at the origin of the signature. As a consequence, the person that owns the private key matching the public key (i.e. the signatory) cannot deny to be at the origin of such signature; this non-repudiation feature is the foundation of any signature (electronic or paper-based).

Another characteristic of digital signatures is that if the signed text has been modified after the signature, the verification of the signature will fail (because the signature computation mixed the private key and the data to be signed the verification computation will always disclose the very same data). (In the illustration

the data in the box cannot be retrieved or replaced or modified by other data until the box is opened). As a consequence, successful signature verification also ensures data integrity.

Of course, there are some technical tricks to ensure that only the person that owns the private key matching the public key is able to create the signature (and not a third person that would be able to imitate the signatory’s signature):

 it is likely impossible to discover the private key from the knowledge of the public key. Any stakeholder in possession of a public key is able to verify that a signed data has been made by the corresponding private key, without being able to play the role of the signatory since (s)he cannot guess the private key. The size of the key is an important parameter for the security of the algorithm.  A different unique key pair is allocated to each signatory.  The signatory shall protect the private key (in the same way as (s)he would not explain to third party how to imitate her signature).

2.3 Certification services as trust foundation for (Q)ES

The technical foundations presented above, alone, are not sufficient to ensure the full confidence in the system. Indeed, trust in signatures relies on the guarantee that a certain Public Key belongs to a particular signatory, owner (and sole controller) of the corresponding private key. For this purpose, an entity, trusted by the community, called a certification authority (also called a Certification Service Provider, CSP, which is a particular type of TSP as defined in the eIDAS Regulation), certifies the link {public key – signatory} in a public key certificate. In general, one finds the information on the identity of the signatory in the certificate, and sometimes one can also find other attributes relating to this person, such as his/her role within an organisation.

The certificate is a signed statement by the CA; the CA’s signature is trusted because the CA’s key is published in a media trusted by the community (the official journal, e.g.). The procedures, techniques and mechanisms put in place to realise such certification services is commonly called Public Key Infrastructure (or PKI). The certificate officialises the link between a signatory and its key pair in the same way an identity card officialises the link between a citizen and his/her handwritten signature represented on the card.

The trust in certificates relies on the quality of the CA and its certification services. The CA must follow sound policies: strong cryptography, secure CA premises and devices, signature creation devices for signatories of a good quality, trusted personnel, insurances, etc.

It also relies in the possibility to revoke certificates that are not trusted anymore and to publish revocation status (i.e. black list of revoked certificates) to verifying parties (i.e. validation services). This can happen if the signatory has lost his/her signature creation device and fears that someone uses it to impersonate him/her.

Finally, trust in CA policies relies on the level of assurance that the CA indeed correctly implements these policies. For this purpose, the CA can be audited.

2.4 The electronic signature process

The signature creation workflow

A signatory, to create a signature in a document, works in a certain environment (e.g. a laptop) to access signing functionalities made of:

a. the signature creation application (e.g. a pdf application residing on the laptop) and b. the signature creation device that i. holds the signature creation data (private key); ii. shall be able to authenticate the signatory (to guarantee his/her sole control on the private key); iii. computes the signature (using the signer's signature creation data); iv. may hold the signing certificate (or unambiguous references to it).

Concretely, how does it work?

1. The signatory prepares the document like any kind of document (e.g. a PDF file).

2. The application prepares the data to be signed (i.e. the PDF) in a condensate (called a hash) and present it to the signature creation device.

3. The signature creation device asks the authorisation to the signatory to sign the data, in general, though a windows that pops up on the screen. The signatory authenticates to the device (e.g. (s)he enters a PIN code, or a fingerprint).

4. The signature creation device computes the signature and sends the result to the application that integrates the signature into the document.

At this stage, it is important to note that in general, the signatory’s certificate is provided with the signature. This enables the identification of the signatory and the verification of the signature since the public key is immediately available from the certificate. If there are attributes relating to the signatory in the certificate, one can also validate these attribute(s) (e.g. the person may sign in quality of director of an organisation and this title is certified), but nothing prevents the signatory to (also) add a sentence in the signed document that says “I'm signing in quality of director”. This is a self-claim similar to what is done in the paper world.

The augmentation for more resilience

The augmentation can be done either by the signatory, or by the relying party or by a TSP that validates or preserve the signature on behalf of the signatory or the relying party. E.g. if someone asks another person

to sign an acknowledgement of debt, it is likely to be the case that the first person has some interest in the preservation of the signature (which is not necessarily the case of the signatory). On the contrary, if the signature is not verified immediately by the relying party, the signatory may have some interest in completing the signature, e.g., with a trusted time stamp in order to provide a trusted evidence of the signing time. By this way it will be difficult for the relying party to reject the signature in case of a subsequent problem with regard to the signature (e.g. expiration of the signing certificate).

2.5 Qualified electronic signatures

As mentioned above, qualified electronic signatures enjoy, all over the EU, the equivalent legal effect of a handwritten signature.

To achieve a QES, the eIDAS Regulation requires a qualified signature creation device (i.e. a signature creation device that follows the requirements listed in the eIDAS Regulation and will be certified accordingly).

In addition, the eIDAS Regulation also requires a qualified certificate for electronic signatures: the qualified certificate follows the requirements listed in the eIDAS Regulation, and the issuing CA will be a qualified trust service provider. Pursuant to the eIDAS Regulation, the CA will be audited and if the Member State in which the CA is established receives a suitable audit report and verifies the eIDAS requirements, the CA will be listed as qualified trust service provider in the corresponding national trusted list.

 Qualified certificates for electronic signatures provides high assurance of the identity of the

signatory

 QSCDs provide high assurance on the security of the signature

Moreover, the eIDAS Regulation offers the possibility to use qualified trust services (QTS) for the validation and/or the preservation of QES. Such services are offered by QTSPs.

There is no obligation to call such QTS for the validation or the preservation of (qualified) signature, but as any other qualified service, their use provide the users with a pretty good legal protection (i.e. in case of litigation the burden of the proof lies on the QTPS).

3. Qualified electronic signature – what key properties does it provide? 3.1 Legal properties

Signing with the same legal value as with a handwritten signature

As presented above, QES benefit from a full legal recognition thanks to the eIDAS Regulation to achieve the same effects as when using a hand-written signature. Such electronic signatures thanks to the obligations set by the eIDAS Regulation on both the TSP managing them (in particular the CAs) and on the underlying technologies: warrant data integrity, identify the signatory with a high level of certainty, and ensure the non-repudiation of signing. At this stage, it is important to note that like handwritten signature, (qualified) electronic signatures are created by human beings (i.e. natural persons). Indeed, under the eIDAS Regulation, a legal person is not legally permitted to electronically sign. Rather, the eIDAS Regulation allows legal persons to electronically seal data. The concept of electronic seal for legal persons is very similar to the concept of electronic signature for natural persons and is the topic of dedicated security guidelines within the series.

3.2 Security properties

Data integrity

As mentioned in the introduction, the use of public key cryptography to implement QES (and AdES in general) ensures data integrity (i.e. any change in the signed data after the signature process is detected).

Data origin authentication

The use of public key cryptography to implement QES (and AdES in general) warrants the proof of origin of the signed data since only the person in possession of the private key can be at the point of origin of data signed with the corresponding public key. For QES, in addition, there is a high level of assurance on the identity of the person owning such private key (see below).

3.3 Functional Properties

Non-repudiation of signing

As mentioned in the introduction, the use of public key cryptography to implement QES (and AdES in general) provides for non-repudiation of having signed.

Secure identification of the signatory

The qualified digital certificate ensures the identification of signatory with a very high level of assurance, thanks to the controls of the TSP on one hand, but also thanks to the requirements on the content of the signatory’s certificate imposed by the eIDAS Regulation.

Creating huge amount of signatures and/or signatures on huge data

The involvement of a human being signatory is not always needed when electronically signing; signing (it applies to QES but more broadly for any type of AdES) may be an automated process. E.g. a director of a hospital, may have to sign hundreds of documents per day. To ease her/his life, his/her signature creation device may be implemented on server where the private key stays activated for several hours; provided

the data to be signed submission process is secure, as well as the access to the server, a perfectly valid signature can be created without the need to enter the director’s PIN code for each and every signature applied.

Also, a signature can be applied to data of any type and any size; a contract in a pdf format, e.g. will only require one single electronic signature to ensure the integrity and non-repudiation of the whole file. No need to sign each and every page like in the paper world, by virtue of the data integrity featured by the Public Key Cryptography technology underlying QES.

3.4 Other Properties

Signing with a signature that is understood and verifiable worldwide

Basic signatures, like non-qualified AdES, benefit from the non-discrimination rule. This means that a Court in an EU Member State cannot reject them automatically as being invalid simply because they are in electronic form. However, their dependability is still lower than that of a QES because the signatory may be required to prove the security of the technology being used if the validity of the signature is disputed before a court. This requires significant costs and efforts that could be avoided with relative ease by opting for the more established and standardised advanced and qualified signature solutions. It may also be the case that the relying parties have no applications or tools to validate such signature, when not based on standards; in such a scenario, the signature may be legally valid and technologically robust, but of limited use.

For these interoperability reasons, QES that are based on recognised EU standards are preferable unless

the parties operate purely in a local context where the acceptance and usability of the chosen signature solution is sufficiently certain.

Beyond the technical interoperability, the eIDAS Regulation also ensures the (international) recognition of electronic signatures. See also the “FAQ” on this topic.

Signing “in quality of”

It is possible to certify elements that are bound to the signatory such as a title (e.g. Director), a link with its employer, etc. Because the QCA is trusted for verifying the information it certifies, the Relying Party can get a high level of confidence in such information conveyed with the signature through the signatory’s certificate.

4. Qualified electronic signature – what properties can it not provide? 4.1 Legal properties not provided by QES

“Signature” by a legal person

As mentioned above (qualified) electronic signatures are performed by human beings (i.e. natural persons). It is not possible for an organisation or a legal person to create a (qualified) electronic signature. Rather, they will use another concept introduced by the eIDAS Regulation, namely the (qualified) electronic seal.

Granting that the content of the signed data is meaningful, fair or true

Exactly like in the paper world, it is not because a contract is signed that the terms of the contract are fair.

4.2 Security properties not provided by QES

Confidentiality

The signature protocol used alone does not provide confidentiality, although the Public Key Cryptography can be used to offer encryption. Indeed, if the signature process presented above is reverted (i.e. someone is using the public key of a recipient to encrypt a text), then only the recipient that owns the correspondent private key can decrypt the text. Like for electronic signature, a certificate attesting the link between the recipient and its key pair is to be provided by a TSP (i.e. a CA). One needs to superpose the two protocols to achieve electronic signature and confidentiality. First the signatory signs and then (s)he may encrypt the signed document to the attention of a recipient, provided (s)he has the encryption certificate of this person. If the signed document needs to be sent to many recipients, then the encryption protocol needs to be repeated as many times as there are recipients.

4.3 Functional properties not offered by QES

Time stamping

Although the technique underlying the (Q)ES can be used by a special sort of “signatory” (i.e. a time stamping authority), a QES does not provide any proof on the signing time; unless a trusted timestamp is added to the signature (see below), the time that is appended to a QES is a self-declaration from the signatory and not an official proof.

4.4 Other properties not offered by QES

Management of delegation

The relying party verifying a signature will not necessarily be ensured that the signatory is authorised to sign (e.g. to commit in the name of a certain organisation). Again this problem is not unique to electronic signatures; it exists in paper signatures as well (and arguably more so, since electronic signatures can more easily convey highly trustworthy identity information).

Electronic signatures do permit the implementation of solutions to this problem by incorporating authorisation management solutions. It is also possible to certify, in the certificate, elements that are bound to the signatory such as a title (e.g. Director), a link with its employer, etc. However, this is not provided by default. And it is not because the title Director is certified that the director is effectively empowered to sign any type of commitments in the name of the organisation (s)he represents.

Eternal integrity

There is no guarantee that the content of the signed document cannot be changed if (long term) preservation features are not implemented (see BASIC / RECOMMENED / ENANCED below).

5. Qualified electronic signature – what are the potential use cases? 5.1 Overview and context of the given examples

In general and to put qualified electronic signatures into context, they only provide signatures. As mentioned above, they do not establish the exact time on when the document was signed, they do not necessarily provide the commitment of a potential legal entity behind the signatory, and they do not confirm delivery of the signed message. Hence, qualified electronic signatures (QES) are most often seen coming in addition of other identification and/or trust services as part of a broader solution.

In this context, and although the properties of QES have been described in the previous sections, the following properties are key for the use case examples mentioned below:

 QES to establish the originator of a signed document.  QES to provide integrity of a signed document.  QES to provide non-repudiation of having signed document.

Those properties allow several “types of use cases” which can be applied in many areas of application as show in the present section. The table below highlight the identified types of use cases. The mapping on areas of applications in no way tries to be exhaustive but only tries to indicate the huge potential of QES.

5.2 Signing a document/message to confirm origin

A first and often forgotten use case is (even if a QES might be considered excessive due to its qualified status) is simply to apply signatures on documents and messages to give proof of origin and integrity. Indeed, in the days of phishing it is for many people very difficult to see if a document or a message really originates from where it seems to come from. Applying qualified electronic signatures on documents/messages can easily and swiftly provide a solution for this.