What It Takes To Truly Delete Data

FiveThirtyEight:

In February of 2014, New York City Mayor Bill de Blasio announced the creation of IDNYC, a municipal identification card primarily designed to ease bureaucratic burdens for the city’s immigrant population. When the card became available a year later, de Blasio described the program as “fraud-proof, secure and appealing to anyone.”
Now privacy advocates and progressives are worried that it also may be appealing to Donald Trump. The president-elect has said he plans to deport up to three million undocumented immigrants, and immigrant advocates are concerned the database of immigrants may be a good place to start. That combined with de Blasio’s vow that New York will remain a sanctuary city  has brought renewed attention to the security of the database. In December, a court barred the city  from deleting the data to protect users’ identities and an ongoing lawsuit ensures that the records continue to be retained today. But there’s an urgent question about the records, fundamental to understanding not just the fate of the data for IDNYC, but all consumer data in the hands of third parties, be they private companies or state departments: Can an entire dataset of important information really be deleted, just like that?