Séminaire de Cryptographie

Accueil     Présentation     Archives

Gildas Avoine

Cracking Passwords with Time-memory Trade-offs

Cryptanalytic time-memory trade-offs were introduced by Hellman in 1980 in order to perform key-recovery attacks on cryptosystems. A major advance was presented at Crypto 2003 by Oechslin, with the rainbow tables that outperform Hellman's seminal work.

After introducing the cryptanalytic time-memory trade-offs, we will present in this talk a new variant of tables, known as fingerprint tables, which drastically reduce the number of false alarms during the attack compared to the rainbow tables. The key point of the technique consists in storing in the tables the fingerprints of the chains instead of their endpoints.

The fingerprint tables provide a time-memory trade-off that is about two times faster than the rainbow tables on usual problem sizes. We will illustrate the performance of the fingerprint tables by cracking Windows NTLM Hash Passwords.