= Hugo Krawczyk
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<Hugo Krawczyk> is a <computer scientist> working on the theory and applications of <cryptography>, including <message authentication> and the design of <cryptographic protocols>.<Hugo Krawczyk profile at the Simons Institute>[Research description.]{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.<Keying Hash Functions for Message Authentication by Mihir Bellare, Ran Canetti and Hugo Krawczyk>[1996 manuscript, Abstract and §§1.1–1.3.]{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.<HMAC-based Extract-and-Expand Key Derivation Function (HKDF) by Hugo Krawczyk and Pasi Eronen>[RFC 5869 §§2.2–2.3 and 3.2.]{ref}
\Image[https://simons.berkeley.edu/sites/default/files/styles/post_card_lg_2x/public/hugo-bio.jpg?h=5be123fc&itok=YjSKRc7H]
{title=<Hugo Krawczyk>, portrait linked from his Simons Institute profile}
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