International Association
for Cryptologic Research

Naveed, Kamara, and Wright\'s recent paper \"Inference Attacks on Property-Preserving Encrypted Databases\" (ACM-CCS 2015) evaluated four attacks on encrypted databases, such as those based on the design of CryptDB (Popa et al., SOSP 2011). Two of these attacks---frequency analysis and l_p-optimization---apply to deterministically encrypted columns when there is a publicly-available auxiliary data set that is \"well-correlated\" with the ciphertext column. In their experiments, frequency analysis performed at least as well as l_p-optimization for p=1, 2, and 3. We use maximum likelihood estimation to confirm their intuition and show that frequency analysis is an optimal cryptanalytic technique in this scenario.