Differences

This shows you the differences between two versions of the page.

--- dcc:pdpsol:pseudonymization [2026/03/23 14:10] – marlon
+++ dcc:pdpsol:pseudonymization [2026/05/13 13:25] (current) – alba
@@ Line 1: / Line 1: @@
-{{indexmenu_n>2}}
+{{indexmenu_n>3}}
-====== Pseudonymization ======
+====== Pseudonymization procedures ======
 ===== Introduction =====
-Pseudonymization is a de-identification procedure during which personally identifiable information is replaced by a unique alias or code (pseudonym). In some situations, the researcher maintains the link between the unique code and the data subject in a keyfile, while in other projects this connection is not necessary.
+Pseudonymization is a de-identification procedure during which personally identifiable information is replaced by a unique alias or code (pseudonym). In some situations, the researcher maintains the link between the unique code and the data subject in a keyfile, while in other projects, this connection is not necessary.
 The manner in which pseudonymization is done varies between projects based on the research setup. It is good practice to describe the process of pseudonymization specific to your research either in your data management plan or a separate Pseudonymization Protocol. You can use the examples below to guide you in this process.
+----
+**Warning:** pseudonymization does not equal anonymization. An anonymized dataset does not allow for the re-identification of data subjects and is therefore no longer considered personal data. Even if all [[https://www.rug.nl/digital-competence-centre/privacy-and-data-protection/gdpr-research/essential-concepts|direct identifiers]] and your pseudonymization key have been replaced or removed, it might still be possible to re-identify some data subjects in your data because, in combination, certain attributes (e.g., combination of height, job occupation and location of data collection) may single out an individual.
 ===== Pseudonymization without a keyfile =====
-This is the simplest form of pseudonymization, where direct identifiers are either removed or replaced by a pseudonymization ID. It can be applied to direct identifiers in a single file or used to connect multiple files.
+This is the simplest form of pseudonymization, in which direct identifiers are either removed or replaced with a pseudonymization ID. It can be applied to direct identifiers in a single file or used to connect multiple files.
 First, assign each data subject in your dataset a unique pseudonymization ID. That ID must be unique, non-informative, and non-derivable from personal data. In Excel, you can generate a randomized list of IDs by entering the following formula in the formula bar:  <color #ed1c24>=SORTBY(SEQUENCE(N), RANDARRAY(N))</color>. Here, <color #ed1c24>SEQUENCE(N)</color> generates numbers from 1 to <color #ed1c24>N</color>, and <color #ed1c24>RANDARRAY(N)</color> randomizes their order. Choose an <color #ed1c24>N</color> larger than your sample size (e.g., for 100 data subjects, <color #ed1c24>N</color> = 1000). Remove all direct identifiers (e.g. names, email addresses, phone numbers) or replace them with these IDs. Use the same ID consistently across related files (e.g., transcripts, survey responses, and other data) to preserve linkability while protecting the identity of your data subjects (Figure 1).
+----
-**Warning:** Pseudonymization does not equal anonymization. Although all direct identifiers have been removed or replaced, it might still be possible to re-identify some data subjects in your data because, in combination, certain attributes (e.g., combination of height, job occupation and location of data collection) may single out an individual.
 **Figure 1: Pseudonymization without a keyfile**
-----
 {{:dcc:pdpsol:pseudonymization:pseudnk.png?direct&400|}}
@@ Line 26: / Line 28: @@
 ==== Creating a keyfile ====
-First, create a pseudonymization keyfile (e.g., in Excel or another UG approved tool available in the University Workplace) that assigns each data subject a unique pseudonymization ID. For the creation of the pseudonymization IDs, you can follow the same steps as described in //Pseudonymization without a keyfile//. Direct identifiers such as names, email addresses, or phone numbers should be stored only in this keyfile (Figure 2) and removed from the research dataset. In the research dataset, remove all direct identifiers or replace them with the pseudonymization IDs.
+First, create a pseudonymization keyfile (e.g., in Excel or another UG-approved tool available in the University Workplace) that assigns each data subject a unique pseudonymization ID. For the creation of the pseudonymization IDs, you can follow the same steps as described in //Pseudonymization without a keyfile//. Direct identifiers such as names, email addresses, or phone numbers should be stored only in this keyfile (Figure 2) and removed from the research dataset. In the research dataset, remove all direct identifiers or replace them with the pseudonymization IDs.
-**Figure 2: Pseudonymization with keyfile**
 ----
+**Figure 2: Pseudonymization with keyfile**
 {{:dcc:pdpsol:pseudonymization:pseudk.png?direct&400 |}}{{:dcc:pdpsol:pseudonymization:pseudnk.png?direct&400|}}
 ==== Managing the keyfile ====
-You must store the keyfile securely in your [[https://www.rug.nl/digital-competence-centre/it-solutions/store-and-archive/university-workplace-storage|X-Drive or Y-Drive]], separate from the research data. Strictly limit access to the keyfile, for example, by using password-protected, encrypted, or stored on a secure server. This ensures that, even if the research dataset is shared or accessed by unauthorized parties, re-identification is only possible if the keyfile is also compromised. Keep track of who is authorized to access the keyfile, and if necessary (e.g. longitudinal research), ensure that there are two people who have access to the key in case one becomes unavailable.
+You must store the keyfile securely in your [[https://www.rug.nl/digital-competence-centre/it-solutions/store-and-archive/university-workplace-storage|X-Drive or Y-Drive]], separate from the research data. Strictly limit access to the keyfile, for example, by using an extra layer of encryption (e.g. using Excel's encryption functionality or [[..:itsol:veracrypt:|Veracrypt]]). This ensures that, even if the research dataset is shared or accessed by unauthorized parties, re-identification is only possible if the keyfile is also compromised. Keep track of who is authorized to access the keyfile, and if necessary (e.g. longitudinal research), ensure that there are two people who have access to the key in case one becomes unavailable.
-Determine whether it is necessary to maintain a link between your research data and the individuals involved. Do not retain the keyfile longer than necessary for your research (e.g., [[https://www.rug.nl/digital-competence-centre/privacy-and-data-protection/gdpr-research/rights-of-human-data-subjects-in-scientific-research|exercising data subjects’ rights]] or informing data subjects about the research).
+Only maintain a link between your research data and the individuals involved if necessary. Do not retain the keyfile longer than necessary for your research (e.g., [[https://www.rug.nl/digital-competence-centre/privacy-and-data-protection/gdpr-research/rights-of-human-data-subjects-in-scientific-research|exercising data subjects’ rights]] or informing data subjects about the research).
-**Warning:** As with the simple procedure, pseudonymization does not equal anonymization. Even without the keyfile, data subjects may still be identifiable if certain attributes in the dataset can be combined to single out an individual (e.g., combination of age, job occupation, and location).
 ===== Double coding =====
@@ Line 43: / Line 45: @@
 This approach reduces the risk of re-identification and protects sensitive information throughout the data transfer process. For guidance on implementing this protocol, contact your [[https://www.rug.nl/digital-competence-centre/contact/|faculty data steward or the DCC]].
+----
 **Figure 3: Pseudonymization with double coding**
-----
 {{:dcc:pdpsol:pseudonymization:pseudnk.png?direct&350|}}{{:dcc:pdpsol:pseudonymization:pseuddc.png?direct&350 |}}{{:dcc:pdpsol:pseudonymization:pseuddc2.png?direct&350 |}}
 ----
 [[dcc:pdpsol:start | → Go back to the Privacy & Data protection home page]]