 Hugo Krawczyk

Hugo Krawczyk is a computer scientist working on the theory and applications of cryptography, including message authentication and the design of cryptographic protocols.^[ref]

With Mihir Bellare and Ran Canetti, Hugo Krawczyk developed HMAC, a message authentication code built from a cryptographic hash function. The scientific problem is that an ordinary public hash function lets anyone recompute a digest after changing a message. A keyed construction lets parties sharing a cryptographic key check authenticity under stated security assumptions.^[ref] Authentication alone does not conceal the message: encryption addresses a different requirement.

With Pasi Eronen, Hugo Krawczyk specified HKDF, an HMAC-based key derivation function. Its extraction step processes input keying material into a pseudorandom key; expansion derives output keying material with application-specific context. For example, a protocol can use distinct context labels for sending and receiving keys, rather than reuse one key for both roles. This separates uses of an existing secret; it does not manufacture secrecy from fully predictable input.^[ref]