Security

National Identification Number

A lifetime identifier a government assigns to each resident, such as Denmark's CPR number or the US Social Security number. It is designed to be stable and widely shared, which makes it a strong identifier and an unsuitable authenticator.

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Why a National ID Number Can Never Be a Secret, and What to Authenticate With Instead

Identifiers and authenticators have opposite requirements. Why knowledge-based verification fails for lifetime ID numbers, and how to move to device-bound and out-of-band factors.

intermediate 6 min read

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