computer science

XAdES

XAdES is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand XAdES rather than just read about it. In short: XAdES (short for XML Advanced Electronic Signatures) is a set of extensions to XML-DSig recommendation making it suitable for advanced electronic signatures. W3C and ETSI maintain and update XAdES together.

Key takeaways

XAdES belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect XAdES to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of XAdES from memory before moving on to harder problems.

Reference excerpt

XAdES (short for XML Advanced Electronic Signatures) is a set of extensions to XML-DSig recommendation making it suitable for advanced electronic signatures. W3C and ETSI maintain and update XAdES together.

Description While XML-DSig is a general framework for digitally signing documents, XAdES specifies precise profiles of XML-DSig making it compliant with the European eIDAS regulation (Regulation on electronic identification and trust services for electronic transactions in the internal market). The eIDAS regulation enhances and repeals the Electronic Signatures Directive 1999/93/EC. EIDAS is legally binding in all EU member states since July 2014. An electronic signature that has been created in compliance with eIDAS has the same legal value as a handwritten signature. An electronic signature, technically implemented based on XAdES has the status of an advanced electronic signature. This means that

it is uniquely linked to the signatory; it is capable of identifying the signatory; only the signatory has control of the data used for the signature creation; it can be identified if data attached to the signature has been changed after signing. A resulting property of XAdES is that electronically signed documents can remain valid for long periods, even if underlying cryptographic algorithms are broken. However, courts are not obliged to accept XAdES-based electronic signatures as evidence in their proceedings; at least in EU, this is compulsory only for "qualified" signatures. A "qualified electronic signature" needs to be doted with a digital certificate, encrypted by a security signature creation device, and the identity of the owner of this signing-certificate must have been verified according to the "high" assurance level of the eIDAS regulation.

Profiles XAdES defines four profiles (forms) differing in protection level offered.

XAdES-B-B (Basic Electronic Signature), The lowest and simplest version just containing the SignedInfo, SignatureValue, KeyInfo and SignedProperties. This form extends the definition of an electronic signature to conform to the identified signature policy. XAdES-B-T (Signature with a timestamp), A timestamp regarding the time of signing is added to protect against repudiation. XAdES-B-LT (Signature with Long Term Data), Certificates and revocation data are embedded to allow verification in the future even if their original source is not available. XAdES-B-LTA (Signature with Long Term Data and Archive timestamp), By using periodical timestamping (e.g. each year) compromising is prevented which could be caused by weakening previous signatures during a long-time storage period. In February 2016, ETSI publishes the document ETSI EN 319 132-1 V1.1.0 as final draft for a European Standard. In this draft, the profiles have been omitted.

See also European Telecommunications Standards Institute (ETSI) XML Signature CAdES, CMS Advanced Electronic Signature PAdES, PDF Advanced Electronic Signature ASiC, Associated Signature Containers (ASiC) Trusted timestamping

References

External links W3C XAdES version 1.1.1 from 2003 ETSI TS 101 903 XAdES version 1.1.1 from 2002 to 2002-12 ETSI TS 101 903 XAdES version 1.2.2 from 2004 to 2004-02 ETSI TS 101 903 XAdES version 1.3.2 from 2006 to 2003-07 ETSI TS 101 903 XAdES version 1.4.1 from 2009 to 2006-15 ETSI TS 101 903 XAdES version 1.4.2 from 2010 to 2012 ETSI TS 101 903 V1.2.2 Technical Specification, XSD and DTD ETSI TS 101 903 V1.3.2 XSD and DTD ETSI TS 101 903 V1.4.1 XSD DSS: GitHub repository CAdES, XAdES and ASiC for Windows in C++ Duuba open source Java library for creating XAdES signatures

Worked examples

Example 1 — a first encounter with XAdES

Start with the simplest possible case. Write down what XAdES claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to XAdES before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about XAdES ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of XAdES

In research: XAdES appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses XAdES in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: XAdES is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cryptography standards, XML-based standards, so understanding it makes those chapters shorter.
In everyday life: Look for XAdES outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “XAdES” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study XAdES in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what XAdES means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain XAdES out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is XAdES in simple terms?

Why does XAdES matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study XAdES?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on XAdES.