Practical Key Search Attacks Against Modern Symmetric Ciphers

Presented at DEF CON 27 (2019), Aug. 9, 2019, 2 p.m. (45 minutes).

In theory, brute force key recovery attacks against modern ciphers like AES should be impractical with the current state of computer hardware. It's often said that recovering an AES key should take longer than the remainder of the life of the sun. However, this assumes that keys are chosen properly, and that there is no way to determine whether a key is the correct one after a candidate key is used to decrypt a captured ciphertext. In practice, these conditions do not always hold. In much the same way that hash functions are impossible to reverse but hash cracking is still a practical attack, in the real world it is often possible to perform practical key search attacks. In this talk, we will discuss the common mistakes and common conditions that allow for practical brute force recovery of keys for modern block ciphers such as AES. We will also discuss optimizations to speed up key search efforts, and present our FOSS tool, which implements our approach.

Presenters:

• Daniel Pagan - Student, Georgia Tech
  Daniel Pagan is a student at Georgia Tech, a DEF CON TV goon, and a Lord in the micronation of Sealand.
• Daniel Crowley / unicornFurnace - Research Baron, X-Force Red   as Daniel "ufurnace" Crowley
  Daniel Crowley is the head of research and a penetration tester for X-Force Red. Daniel denies all allegations regarding unicorn smuggling and questions your character for even suggesting it. Daniel is the primary author of both the Magical Code Injection Rainbow, a configurable vulnerability testbed, and FeatherDuster, an automated cryptanalysis tool. Daniel enjoys climbing large rocks and is TIME magazine's 2006 person of the year. Daniel has been working in the information security industry since 2004 and is a frequent speaker at conferences including Black Hat, DEF CON, Shmoocon, and SOURCE. Daniel does his own charcuterie and brews his own beer. Daniel's work has been included in books and college courses. Daniel also holds the noble title of Baron in the micronation of Sealand.

Links:

• https://defcon.org/html/defcon-27/dc-27-speakers.html#Crowley
• https://infocon.org/cons/DEF CON/DEF CON 27/DEF CON 27 video and slides/DEF CON 27 - Daniel ufurnace Crowley - Practical Key Search Attacks Against Modern Symmetric Ciphers.mp4
• https://infocon.org/cons/DEF CON/DEF CON 27/DEF CON 27 video and slides/DEF CON 27 - Daniel ufurnace Crowley - Practical Key Search Attacks Against Modern Symmetric Ciphers.srt (subtitles)
• https://www.youtube.com/watch?v=ubzNkvq6lVo

Similar Presentations:

• DEF CON 28 (2020) Virtual / Exploiting Key Space Vulnerabilities in the Physical World
• Black Hat USA 2022 / Demystifying Key Stretching and PAKEs
• Black Hat Europe 2015 / Unboxing the White-Box: Practical Attacks Against Obfuscated Ciphers