Records / De-identification rules
Stand-ins from a secret key you keep, never a plain hash
Each stand-in number comes from a keyed hash (HMAC-SHA-256) under a 256-bit key made on your computer, looked up in a table that holds hashes, never names. A new key for each delivery means two buyers' copies cannot be joined.
Dated Sep 2023Source checked 15 Oct 2026Page out of reach at the last check, 16 Oct 2026Basis: our standard
In the source's own words
“Hashing without a key generally does not confer security because an attacker can brute force all possible values to be hashed.”
Where it was read
NIST SP 800-188, p. 51, checked Sep 2023
HHS, Guidance on de-identification, checked 26 Nov 2012
Everything read from this source (5)Archived copy, 5 Oct 2026
NIST IR 8053, p. 17 (New York taxi data, 2014), checked Oct 2015
Everything read from this source (3)Archived copy, 10 Oct 2026
Also read from the same source
Figures it counts in
It is shown on its own, not counted into a figure.
Cited in this guide