Nitelikli elektronik imzaların kullanılabilirliğinin değerlendirilmesi: Sistematize edilmiş kullanım durumları ve tasarım paradigmaları
Evaluating the usability of qualified electronic signatures: Systematized use cases and design paradigms
Yazar: MUSTAFA ÇAĞAL
Danışman: PROF. DR. KEMAL BIÇAKCI
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Bilişim Uygulamaları Ana Bilim Dalı / Bilgi Güvenliği Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Bilgisayar Mühendisliği Bilimleri-Bilgisayar ve Kontrol = Computer Engineering and Computer Science and Control
Dizin: Elektronik imza = Electronic signature

Özet:
El yazısı imzalara yasal olarak eşdeğer olmalarına rağmen, Nitelikli Elektronik İmzalar (QES) henüz önemli bir pazar başarısı elde edememiştir. QES, kağıt tabanlı sözleşmelere olan bağımlılığı azaltmak, güvenli dijital uygulamaları etkinleştirmek ve kamu hizmetlerini standartlaştırmak konusunda önemli bir potansiyele sahiptir. Ancak, geniş kullanım alanlarına sahip olmasına rağmen  kullanılabilirliği hakkında sınırlı çalışma bulunmaktadır. Tez çalışması bahse konu boşluğu gidermek için hazırlanmıştır. Tez kapsamında çalışma benzeri kullanılabilirlik çalışmaları aracılığıyla Nitelikli Elektronik İmzaların güçlü ve zayıf yönlerini değerlendirme gerekliliğini vurgulanmış, QES kullanım durumları sistematize edilmiş,  kullanım durumlarını destekleyen tasarım paradigmaları kategorize edilmiştir. Ayrıca, dört farklı QES sistemindeki kullanım durumları üzerinde yürütülen bilişsel gözden gözden geçirme sonucu elde edilen bulgular sunulmuştur.
Araştırma soruları şu şekildedir:
1.Türkiye ve Avrupa Birliği genelinde Nitelikli Elektronik İmzaların(QES) tüm kullanım durumları nelerdir? "Kullanım durumları" terimi kullanılırken, standart kullanıcıların yerine getirmesi gereken görev kümesinden bahsedilmektedir.
2.Bu kullanım durumlarıyla ilişkili tasarım paradigmaları, seçenekler ve alt kullanım durumları nelerdir?
3.Bu kullanım durumları ve tasarım paradigmalarını göz önünde bulundurularak, pratik QES sistemlerinin güçlü ve zayıf yönleri ile kullanılabilirlik zorlukları nelerdir?
Farklı QES sistemlerinin güçlü ve zayıf yönlerini değerlendirme konusunda bir potansiyele sahip oldukları için, araştırmanın odak noktası olarak Avrupa Birliği ve Türkiye seçilmiştir. QES süreçlerinde yer alan temel aktörler ayrıntılı olarak ele alınmış ve QES süreçlerindeki çok sayıda aktörün kullanılabilirliği etkileyebileceği keşfedilmiştir. QES kullanım durumları, bu kullanım durumlarını destekleyen alt kullanım durumları ve tasarım paradigmaları belirlenmiş ve kategorilere ayrılmıştır. Müteakiben toplamda 36 bilişsel gözden geçirme gerçekleştirilmiştir. 
Çalışmanın en önemli bulgusu, uzaktan imzaların diğer alternatiflere kıyasla daha kullanılabilir olmasıdır.
Nitelikli Elektronik İmzaları standart kullanıcılar için daha çekici bir seçenek haline getirmek maksadıyla, Türkiye'de ve Türkiye benzeri henüz regüle edilmemiş diğer ülkelerde uzaktan imzaların yasallaştırılması gerektiği sonucuna ulaşılmıştır. Bu tezin, Nitelikli Elektronik İmzaların kullanılabilirliği üzerine araştırmaların önemli ölçüde genişletilmesi için bir temel oluşturacağı değerlendirilmektedir.

Abstract:
Despite being legally equivalent to handwritten signatures, Qualified Electronic Signatures (QES) have not yet achieved significant market success. QES offer substantial potential for reducing reliance on paper-based contracts, enabling secure digital applications, and standardizing public services. However, there is limited information on their usability despite the extensive range of use cases. To address this gap, we systematize QES use cases and categorize the system designs implemented to support these use cases, emphasizing the necessity to evaluate their respective strengths and weaknesses through usability studies. Additionally, we present findings from cognitive walkthroughs conducted on use cases across four different QES systems.
Research questions as follows: 
1.What are the Qualified Electronic Signatures (QES) use cases specifically across the Türkiye and European Union? While using the term "use cases", we refer to the set of tasks that standard users must accomplish.
2.What are the design paradigms, options, sub use cases associated with these use cases?
3.Considering these use cases and design paradigms, what are the strengths and weaknesses as well as the usability challenges of practical QES systems? 
In some countries like the USA and China, while there are electronic signature laws and regulations, the specific implementation of Qualified Electronic Signature (QES) systems is not clearly defined. Conversely, in the EU, the eIDAS Regulation governs QES, outlining available systems that include remote signatures, along with traditional methods like QES tokens and mobile signatures. In contrast, Türkiye's valid QES systems do not incorporate remote signatures. Thus, We selected the European Union and Türkiye as the focal points of our research due to the promising potential for evaluating the strengths and weaknesses of different QES systems. 
The initial step of our method is discussing the QES term, key actors and related work. Our second step is identifying use cases and system designs implemented to support these use cases (design paradigms) of QES. The third step is applying cognitive walkthroughs to use cases. The final step is to provide a short discussion of the key findings. We conducted 36 cognitive walkthroughs in total.
A cognitive walkthrough is a measurement method in which experts perform tasks done by users in real life to detect deficiencies. The tasks are predefined, it is simply a simulation of real life. In more precise terms, the cognitive walkthrough method involves experts attempting to behave like standard users to gain insights into user behavior and detect deficiencies. We selected the cognitive walkthrough method for two reasons: First, cognitive walkthroughs are effective tools for detecting usability issues, and second, their task-oriented structure enables researchers to test more systems and use cases. This method allowed us to test 4 practical QES systems, 5 use cases, 14 sub use cases, and 36 design paradigms, which exceeds the solutions and tasks examined in most usability studies. Usability studies mostly concentrate on a specific task.
To enhance the clarity of our study, we have developed a user persona named Hasan. Hasan is a dual citizen of Germany and Türkiye. In Germany, he is known as Hans to individuals and colleagues. Hasan resides in Türkiye and holds the position of Finance Team Head at a company in Istanbul. This company operates on a global scale, requiring Hasan to travel frequently. He also has financial expenditure responsibilities. Hasan must sign expenditure documents, which are then forwarded to the bank for company transactions to take place. Hasan has an adequate understanding of technology and he can comprehend fast and utilize new technologies as a means of conducting business. Hasan has two mobile numbers: one from a Mobile Service Operator (MSO) in Türkiye and another from an MSO in Germany. Additionally, he efficiently utilizes the e-government structure. We believe that our research encompasses all possible options for Hasan to utilize Qualified Electronic Signatures.
Our research was carried out by two authors: one is an academic researcher with a Ph.D. in information systems, and the other is a Master's student who holds the position of an IT Team Leader in an organization. The IT Team Leader is very familiar with the QES landscape, effectively utilizing QES and incorporating its usage within the company as part of his responsibilities. The research was segmented into three sub-processes: identification of QES use cases, categorization and enumeration of system designs, and exploration of weaknesses, strengths, and usability challenges. Initially, each sub-process was carried out individually, followed by discussions to note any disagreements. These disagreements were then addressed through verbal discussions with both standard QES users and in computer science classes. Each sub process was completed prior to researching the next one. 
Our findings are:  
1.QES tokens, QES in the national IDs, and mobile signatures are legally recognized in Türkiye. However, these solutions have more usability limitations compared to remote signatures. Remote signature is legitimate option within the European Union.
2.Both QES tokens and QES in the national IDs necessitate users to carry physical assets, such as USB sticks or cards, card readers. However, remote signatures do not necessitate users to carry physical assets.
3.It is impossible to obtain QES either through national IDs or as mobile signatures via online means. QES in the national ID requires a visit to the National General Directorate of Population and Citizenship Affairs offices, and obtaining mobile signatures requires a visit to authorized mobile service operator offices. Furthermore, there are a limited number of authorized mobile service operator offices.
4.QES tokens can be obtained online but requires a setup. Some of the required programs are specific to each operating system type. Also, device or card reader drivers need to be installed. This requirement prevents the solution from being device-agnostic. However, remote signatures are device agnostic; users can utilize the solution via various devices.
5.QES tokens and QES in the national IDs can be used to create signatures on the web. However, even in web use cases, users must download a browser extension or another desktop application because web applications must communicate with USB ports. Remote signatures are browser-agnostic; users can utilize the solution via various browsers. Users are not required to accomplish additional setup or installation. Extensions, drivers, and desktop applications are not required.
6.Mobile signatures are not independent solutions. They can only be utilized with third parties. However, each remote signing service provider offers its web application, making remote signatures an autonomous option. Third parties are unnecessary.
7.Remote signatures also have an advantage over the others with respect to verification. Service providers are listed in Microsoft Trust Center and European Union Trusted Lists (EUTL), so shared signed documents are automatically verified. However, for others, verification is only possible in local solutions. Automatic signature verifications in third parties fail. This situation may result in feelings of insecurity.
8.The remote signature documentation includes mostly up-to-date information and comprehensive how-to videos. However, the documentation is not well-prepared and up-to-date in other options. Furthermore, for mobile signatures, the available information is limited to website blog content and a frequently asked questions (FAQ) section.
9.QES token and QES in the national ID management programs seem unpolished whereas there is no need to utilize management software for remote signature solutions.
10.Mobile signature requires users to have compatible 128K SIMs. If the SIM card is incompatible, it needs to be exchanged with a Mobile Signature Compatible 128K SIM card.
11.Because remote signatures are not valid in Türkiye at the moment, it is impossible to use them for authentication in E-government or mobile banking.  
Our main finding is that remote signatures are more usable compared to other alternatives. Based on our research, we suggest legalizing remote signatures in Türkiye and other countries where they have not yet been authorized, to make qualified electronic signatures a more attractive option.
We anticipate that this work will serve as a foundation for a significant expansion of research into the usability of Qualified Electronic Signatures.