Random-Access AEAD for Fast Lightweight Online Encryption
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Presented at Real World Crypto 2026 by
A ubiquitious problem in large-scale production environments is online encryption of large messages (e.g., databases, video streams, etc.), that is, encryption while using a small amount of memory. While straightforward when only (unauthenticated) encryption is required---say, by encrypting/decrypting in chunks, using a standard encryption scheme---this is more challenging in the presence of active attackers, who may drop or reorganize ciphertext segments arbitrarily. Moreover, many uses cases additionally require both encryption and decryption to be random access, meaning that messages (resp., ciphertexts) can be encrypted (resp., decrypted) in any order. The purpose of this talk is to present the design of FLOE (Fast Lightweight Online Encryption), a new random-access online AEAD scheme. FLOE was designed in close collaboration with Snowflake, a leading cloud company, where it is slated to be deployed in production to protect sensitive user data. Requiring online encryption of large files, Snowflake encountered a number of real-world challenges with existing schemes, which motivate the design of a new construction.