Techniques are described for generating semi-random private transaction identifiers for users that are meaningful to data providers and can be used by data providers to perform internal queries for user data. A user provides input to an identity management service indicating the user's consent to link their user account at the identity management service to one or more data providers. The identity management service stores a group blinded transaction identifier (GBTI) based on transaction identifiers generated by one or more data providers. When the user desires to obtain a service from a service provider, the user obtains GBTI-derived value from the identity management service and sends it to the service provider. The service provider sends the GBTI-derived value (and possibly other information) to the data provider to prove that it has the user's consent to obtain desired data or insights about the user but without infringing the user's privacy.