Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Data Management for a Digitally-supported Examination Process Bachelor’s Thesis – Final Talk Kaloyan Zdravkov 30.09.2015 Chair for Network Architectures and Services Department of Informatics Technische Universit¨ at M¨ unchen Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 1
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Outline Introduction The exam support system Authentication and encryption Data management Data transfer Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 2
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Introduction Approaching the digitalization of the examination process Related Work: ◮ Fully digital exams ◮ Multiple choice hand-written exams with digital grading ◮ Systems for handling events before an exam, e.g. registration and finding rooms This thesis is about: ◮ Digitally-identifying exam papers ◮ Digitally-supporting the events during a classical pen-and-paper exam ◮ Attendance checking ◮ Logging breaks ◮ Exam hand in ◮ Supervising students Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 3
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Introduction Motivation A digitally-supported examination process advantages: ◮ Reducing errors when assigning grades ◮ The names of the students are not disclosed ◮ Harder to impersonate someone else ◮ Faster counting of exam papers at the end of the exam ◮ Pinpointing a student who did not hand in his exam ◮ Exam protocols will become fully electronic, thus easier to manage Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 4
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Introduction Digitally-identifying an exam paper with a QR code A QR code uniquely identifies the subject, date and student. → ◮ IN0010-20150612- S0003 Why a QR Code? ◮ Built-in error correction recovers data loss as high as 30% ◮ 2-Dimensional - conveys 200 times more data than a 1-Dimensional code Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 5
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Introduction Goals of the thesis The task of digitizing the whole examination process was split in two parts. This thesis covers: ◮ The task of data management for events during the exam ◮ Developing the server application ◮ Developing the data management functionality of the client application The thesis Inspection and Privacy Aspects for a Digitally-supported Examination Process by Stefan Aicher approaches: ◮ Digitizing the events after the exam – digitally scanning and grading a corrected exam ◮ Developing GUI for the client application ◮ Detailed view of the data privacy aspects Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 6
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen The exam support system Architecture Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 7
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen The exam support system Legal aspects Mobile phones are: ◮ Untrusted ◮ Deal with sensitive data – identifiers, linkable to persons The German law states that: ◮ If a mapping exists, between an identifier and a person – the identifier is a pseudonym ◮ Encryption is also pseudonymization – the encrypted data can be mapped to a person with the key ◮ Only depending on the context a pseudonym can be considered as personal data ◮ If the mapping is substantially complicated, then the pseudonyms are not considered personal Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 8
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Authentication and encryption The crypto library libsodium Libsodium’s advantages ◮ High-level crypto API ◮ Small and proven set of algorithms Public-key authenticated encryption in libsodium ◮ Encryption – stream cipher XSalsa20 ◮ Mutual authentication – Diffie–Hellman key exchange Curve25519 ◮ Data integrity and authenticity – HMAC function Poly1305 Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 9
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Authentication and encryption Pairing of phones ◮ Sever’s public key should only be accessible from the phones ◮ Embed the key in a QR code, displayed on the exam laptop Additional security measures ◮ Show a list of every authenticated/paired phone with identifying information ◮ Log which phone triggered the respective event in the database ◮ Assign aliases to every phone for quick discovery Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 10
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Authentication and encryption Phone overview Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 11
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Data Management Object-relational mapping Requirements: ◮ Data model easily modifiable ◮ Database exchangeable Solution: The ORM framework for Java – Hibernate ◮ Mapping objects from OOP language to tables in an RDBMS ◮ The developer only writes java classes - the underlying DB schema is created automatically ◮ The data model is changed only in the Java classes ◮ The application is fully database-independent Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 12
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Data transfer Consistency Every triggered exam event should reach the server ◮ Wi-Fi connectivity lost - with a system event messages are re-sent when the network is up again ◮ Server is down - messages are timeouted and retried ◮ The client app has crashed - all messages are stored, encrypted with the established shared key ◮ If there are unsent messages at the end of the exam, they can be uploaded to the server via cable It is important when the exam event was triggered ◮ Timestamping should be done on the clients ◮ Clients may not have correct time, so they should be synchronized Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 13
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen Data transfer Time synchronization It is assumed that the server will have precise time reference which the clients will synchronize to. 1. The time of the client is acquired 2. A request for the server’s time is sent and the time when the response arrived is stored 3. The transmission delay is calculated by subtracting the time in step 1 from step 2 and divided by two 4. The time difference of client and server is calculated and the transmission delay is added. 5. Steps 1 through 4 are repeated for 3-5 times and the median delay is calculated 6. Iterations with a higher delay than one standard deviation are discarded 7. The results are averaged with arithmetic mean Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 14
Chair for Network Architectures and Services Technische Universit¨ at M¨ unchen DEMO Kaloyan Zdravkov – Data Management for a Digitally-supported Examination Process 15
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