DUHK attack allows hackers obtain encryption code used inside VPNs & web sessions

DUHK (Don't Use Hard-coded Keys) is the part of a crypto-related vulnerability reported this month after KRACK Wi-Fi attack and ROCA factorization charge.DUHK attack allows hackers obtain encryption code used inside VPNs & web session.DUHK — Ingest Use Hard-coded Keys — is a different 'non-trivial' cryptographic implementation vulnerability that could permit attackers to obtain encryption keys that defend VPN links and web browsing settings.

DUHK attack enables hackers to secure encryption code used inside VPNs & web concourses

The vulnerability concerns products from dozens of merchants, including Fortinet, CISCO, Tech Guard, whose devices rely on ANSI X9.31 RNG — an outdated pseudorandom number propagation algorithm — 'in agreement with a hard-coded seed key.' before growing eliminated from the list of FIPS-approved pseudorandom number rank algorithms in January 2016, ANSI X9.31 RNG was involved into various cryptographic measures over the last three decades.Some vendors store this 'secret' seed value hard-coded into the source code of their products, leaving it vulnerable to firmware reverse-engineering.Pseudorandom number generators (PRNGs) don’t generate random numbers at all.

 Instead, it is a deterministic algorithm that produces a sequence of bits based on initial secret values called a seed and the current state. It always produces the same distribution of bits for when used with same initial values.


Created by cryptography researchers — Shaanan Cohney, Nadia Heninger, and Matthew Green — DUHK, a 'state recovery attack,' allows man-in-the-middle attackers, who already know the seed value, to recover the current state value after observing some outputs.

Using both values in hand, attackers can then use them to re-calculate the encryption keys, allowing them to recover encrypted data that could 'include sensitive business data, login credentials, credit card data and other confidential content.'

"In order to demonstrate the practicality of this attack, we develop a full passive decryption attack against FortiGate VPN gateway products using FortiOS version 4." researchers said.

"scans found maybe 23,000 devices with a publicly visible IPv4 address running a vulnerable version of FortiOS."

Here below you can check a partial list (tested by researchers) of affected devices from various vendors:

Some security researchers have published a short blog post and technical researcher paper on a dedicated website for DUHK attack.