Safely Turn Authentication Credentials Into Entropy (STACIE)

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Last updated 2015-11-23 (latest revision 2015-05-22)
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This document specifies a method for Safely Turning Authentication Credentials Into Entropy (STACIE) using an efficient Zero Knowledge Password Proof (ZKPP), and is provided as a standalone component suitable for use as a building block in other protocol development efforts. The scheme was created to fill the emerging need for a standard which allows a single low entropy password to be used for user authentication and the derivation of strong encryption keys. The design is modular, and is conservative in its use of an arbitrary one-way cryptographic hash function. The security of the scheme depends on the difficulty associated with reversing the hash function output back into the plaintext input. STACIE attempts to make discovering the plaintext input through the use of brute force more difficult by linking the amount of processing to the length of a user's plaintext password. The shorter the plaintext password the more processing time per attempt with the amount of additional, artificially required, work scaling exponentially for each character.


Ladar Levison (

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