Function: pseudonymize()

pseudonymize(id, ctx): string

Replace an identifier with a consistent keyed-HMAC surrogate. The same input under the same key always yields the same surrogate (linkage preserved); the surrogate is not reversible without the key (collision-resistant, key-dependent). Domain-separated from keyedHash.

Parameters

id

string

The identifier to pseudonymize (MRN, beneficiary number, account number).

ctx

DeidContext

The de-identification context holding the consumer's key.

Returns

string

A lowercase-hex surrogate, consistent per (key, id).

Example

import { pseudonymize, createDeidContext } from "@cosyte/deid";

const ctx = createDeidContext({ key: "secret" });
pseudonymize("MRN-123", ctx) === pseudonymize("MRN-123", ctx); // => true (consistent)