I think another problem is that we even call any of that "anonymization". If you replace "foobar" with "1", you haven't anonymized anything. At best, you have p

I think another problem is that we even call any of that "anonymization". If you replace "foobar" with "1", you haven't anonymized anything. At best, you have pseudomized your data. Whether you use hashing or a secret mapping function, as long as identity within your dataset is preserved, what you are generating are pseudonyms.