Detecting Encryption Vulnerabilities with Lossless Compression

Abstract

Ciphertext entropy is a key property for detecting the use of insecure encryption modes such as Electronic Code Book (ECB) and for testing symmetric=key cryptographic algorithms. This paper discusses the use of lossless compression utilities as a proxy measurement for entropy and its use in detecting a limited set of encryption vulnerabilities. We also note the use of off-theshelf algorithms yields a teaching tool for Information Technology and Cybersecurity students. Finally, small and consistent differences between encryption modes provide the potential to identify the encryption algorithm from compression factors.