Prevalent Internet protocols require reliable cryptographic algorithms for approving mutual keys to use for bargaining safe connections. Internet protocols such as secure shell (SSH) and hypertext transfer protocol secure (HTTPS) frequently use the Diffie-Hellman key exchange algorithm (DH-KEA). But how dependable is DH-KEA? Adrian et al. perform experiments to examine probable security flaws. The authors introduce Logjam, an attack on the transport layer security (TLS) that empowers a man-in-the-middle attack to relegate connections to “export-grade” cryptography and compromise the secrecy and veracity of application data. Any attacker who can compute a secret key might use it to acquire the connection and master keys, and then apply these keys to finalize the handshake with a client.

How secure is DH-KEA in protocols that are immune to downgrade connections? They discuss an algorithm with precomputations for efficiently computing separate discrete logarithms in near real time. A precomputation involves the choice of polynomial selection, sieving, and linear algebra; it relies on a prime number and a descent process for computing the distinct logarithms. The algorithm was used to examine the susceptibility of the standard Internet key exchange, SSH, and TLS protocols.

The authors present tangible recommendations for averting Logjam and downgrade attacks. DH-KEA should use primes of at least 1024 bits. Network and systems creators should shift to using the elliptic curve DH-KEA to help circumvent every recognized viable cryptanalytic attack. Cryptographers and creators of systems should collaborate and work as a team to develop secure systems for new agile business applications. So, network and systems administrators, are your current configurations of DH-KEA secure in practice today?