Quiz Entry - updated: 2026.07.14
Where do hash functions fit in the taxonomy of cryptographic primitives according to Prof. Ueli Maurer?
Hash functions belong to the "Unkeyed" category of cryptographic primitives — alongside one-way functions and random bit generators.
* Three columns by key usage — hash functions sit in the unkeyed column, next to one-way functions and RNGs. *
The three categories of cryptographic systems and primitives:
| Unkeyed | Secret-Key | Public-Key |
|---|---|---|
| No secret parameters | Two+ entities share a common secret | Individual secret keys, public keys authenticated |
| One-way functions | Symmetric ciphers | Public-key cryptosystems |
| Hash functions | Message authentication codes (MAC) | Digital signature schemes |
| Random bit generators | Pseudo-random bit generators | Various protocols |
Important nuance: While hash functions are classified as "unkeyed," we've seen that:
- Keyed hash constructions exist (MAC, HMAC) — these are in the Secret-Key column
- The classification refers to the primitive itself, not how it's used in a larger construction
- Block ciphers (Secret-Key) can also be used to build hash functions (Unkeyed), e.g., in CBC-MAC