# Measuring re-identification and disclosure risk

Re-identification risk analysis, or just risk analysis, is the process of analyzing sensitive data to find properties that might increase the risk of subjects being identified. You can use risk analysis methods before de-identification to help determine an effective de-identification strategy or after de-identification to monitor for any changes or outliers.

Cloud Data Loss Prevention (DLP) can compute four re-identification risk metrics: k-anonymity, l-diversity, k-map, and δ-presence. If you're not familiar with risk analysis or these metrics, see the risk analysis concept topic before continuing on.

This section provides overviews of how to use Cloud DLP for risk analysis of structured data using any of these metrics, plus other related topics.

## Calculate re-identification risk

Cloud DLP can analyze your structured data stored in BigQuery tables and compute the following re-identification risk metrics. Click the link for the metric you want to calculate to learn more.

Metric Description
k-anonymity A property of a dataset that indicates the re-identifiability of its records. A dataset is k-anonymous if quasi-identifiers for each person in the dataset are identical to at least k – 1 other people also in the dataset.
l-diversity An extension of k-anonymity that additionally measures the diversity of sensitive values for each column in which they occur. A dataset has l-diversity if, for every set of rows with identical quasi-identifiers, there are at least l distinct values for each sensitive attribute.
k-map Computes re-identifiability risk by comparing a given de-identified dataset of subjects with a larger re-identification—or "attack"—dataset.
δ-presence Estimates the probability that a given user in a larger population is present in the dataset. This is used when membership in the dataset is itself sensitive information.

## Calculate other statistics

Cloud DLP can also compute numerical and categorical statistics for data stored in BigQuery tables using the same `DlpJob` resource as the risk analysis APIs.

Metric Description
Numerical statistics Determines minimum, maximum, and quantile values for an individual BigQuery column.
Categorical numerical statistics Computes categorical numerical statistics for the individual histogram buckets within a BigQuery column.