Paper 2014/155

Honey Encryption: Security Beyond the Brute-Force Bound

Ari Juels and Thomas Ristenpart

Abstract

We introduce {\em honey encryption} (HE), a simple, general approach to encrypting messages using low min-entropy keys such as passwords. HE is designed to produce a ciphertext which, when decrypted with any of a number of {\em incorrect} keys, yields plausible-looking but bogus plaintexts called {\em honey messages}. A key benefit of HE is that it provides security in cases where too little entropy is available to withstand brute-force attacks that try every key; in this sense, HE provides security beyond conventional brute-force bounds. HE can also provide a hedge against partial disclosure of high min-entropy keys. HE significantly improves security in a number of practical settings. To showcase this improvement, we build concrete HE schemes for password-based encryption of RSA secret keys and credit card numbers. The key challenges are development of appropriate instances of a new type of randomized message encoding scheme called a {\em distribution-transforming encoder} (DTE), and analyses of the expected maximum loading of bins in various kinds of balls-and-bins games.