Compare the approaches to privacy in medical research with those in commercial marketing.
anonymization
Because of the ease of data aggregation, all data for individuals or small groups needs to be treated as if it was personal data.
I needed a one-way method of generating a unique key for each subject name that would not permit the reverse process, of working out the name for a given key: something known as a ‘one-way hash key’.
The Eclectic Light Company 