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Balloon hashing is a key derivation function presenting proven memory-hard password-hashing and modern design. It was created by Dan Boneh, Henry Corrigan-Gibbs (both at Stanford University) and Stuart Schechter (Microsoft Research) in 2016. It is a recommended function in NIST password guidelines.
The authors claim that Balloon:
- has proven memory-hardness properties,
- is built from standard primitives: it can use any standards non-space-hard cryptographic hash function as a sub-algorithm (e.g., SHA-3, SHA-512),
- is resistant to side-channel attacks: the memory access pattern is independent of the data to be hashed,
- is easy to implement and matches the performance of similar algorithms.
There are three steps in the algorithm:
- Expansion, where an initial buffer is filled with a pseudorandom byte sequence derived from the password and salt repeatedly hashed.
- Mixing, where the bytes in the buffer are mixed time_cost number of times.
- Output, where a portion of the buffer is taken as the hashing result.
- Boneh, Dan; Corrigan-Gibbs, Henry; Schechter, Stuart (2016-01-11). "Balloon Hashing: A Memory-Hard Function Providing Provable Protection Against Sequential Attacks". ePrint. 2016 (027). Retrieved 2019-09-03.
- "Balloon Hashing". Stanford Applied Crypto Group. Stanford University. Retrieved 2019-09-03.
- NIST SP800-63B Section 188.8.131.52
- Research prototype code on Github
- Python implementation
- Alwen; Blocki. "Efficiently Computing Data-Independent Memory-Hard Functions". ePrint. 2016 (115).
- Alwen; Blocki. "Towards Practical Attacks on Argon2i and Balloon Hashing". ePrint. 2016 (759).