Imperfect Forward Secrecy: How Diffie-Hellman Fails in Practice David Adrian¶ Karthikeyan Bhargavan∗ Zakir Durumeric¶ Pierrick Gaudry† Matthew Green§ J. Alex Halderman¶ Nadia Heninger‡ Drew Springall¶ Emmanuel Thomé† Luke Valenta‡ Benjamin VanderSloot¶ Eric Wustrow¶ Santiago Zanella-Béguelink Paul Zimmermann† ∗ INRIA Paris-Rocquencourt † INRIA Nancy-Grand Est, CNRS, and Université de Lorraine k Mi