Tema: cryptography
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Encryption at rest: what it protects against and what it does not
Volume encryption protects data on stolen or discarded drives and on media that leaves the building; while the system is running and mounted, every process with read access sees plaintext, so it does nothing against SQL injection, a stolen application credential or a compromised host. Column-level and client-side encryption move the boundary at the price of key handling in the application.
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Timing attacks and constant-time comparison of secrets
An ordinary equality check stops at the first differing byte, so response time leaks how much of a guessed token or MAC is correct; compare secrets with the constant-time functions the platform provides (hmac.compare_digest, crypto.timingSafeEqual, subtle.ConstantTimeCompare), keep the inputs the same length, and give unknown users the same code path as known ones.
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Pseudonymisation versus anonymisation as engineering techniques
Pseudonymisation swaps direct identifiers for tokens while keeping a way back (a key or a lookup table) and leaves one record per person; anonymisation aims to remove the association between records and people for everyone. Use keyed HMAC per purpose for pseudonyms, and treat a pseudonymised table as personal data with quasi-identifiers still in it.
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