Security Experts:

Connect with us

Hi, what are you looking for?


Data Protection

Protection Against Side-Channel Attacks Added to OpenSSH

Protection against Spectre, Meltdown, Rowhammer,

Protection against Spectre, Meltdown, Rowhammer, RAMBleed and other side-channel attacks has been added to OpenSSH.

These recently uncovered attack methods can allow malicious actors to obtain passwords, encryption keys and other sensitive information from memory by leveraging bit flips or speculative execution.

OpenSSH, the free and open source version of the Secure Shell (SSH) tools designed for securely controlling devices and transferring data, now includes a mechanism designed to protect private keys at rest in memory, said OpenSSH developer Damien Miller.

Private keys, when not in use, are now encrypted with a symmetic key derived from a large “prekey” consisting of random data, Miller said. In order to obtain the protected private key, an attacker would first need to recover the entire prekey, which is not an easy task due to the bit error rates in current side-channel attack methods.

“Implementation-wise, keys are encrypted ‘shielded’ when loaded and then automatically and transparently unshielded when used for signatures or when being saved/serialised,” Miller explained. “Hopefully we can remove this in a few years time when computer architecture has become less unsafe.”

In the case of the recently disclosed RAMBleed, researchers demonstrated the impact of the attack by targeting OpenSSH and leaking a 2048-bit RSA key. However, they have highlighted that OpenSSH was merely a convenient target for demonstrating RAMBleed and it’s not more vulnerable compared to other software.

Related: Researchers Find a Dozen Undocumented OpenSSH Backdoors

Related: OpenSSH Vulnerability Exposes Servers to Brute Force Attacks

Related: OpenSSH Patches Serious Information Disclosure Flaw

Written By

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

Click to comment

Expert Insights

Related Content

Application Security

Cycode, a startup that provides solutions for protecting software source code, emerged from stealth mode on Tuesday with $4.6 million in seed funding.

Malware & Threats

Microsoft plans to improve the protection of Office users by blocking XLL add-ins from the internet.

Cloud Security

VMware vRealize Log Insight vulnerability allows an unauthenticated attacker to take full control of a target system.

IoT Security

Lexmark warns of a remote code execution (RCE) vulnerability impacting over 120 printer models, for which PoC code has been published.

Mobile & Wireless

Apple rolled out iOS 16.3 and macOS Ventura 13.2 to cover serious security vulnerabilities.

Email Security

Microsoft is urging customers to install the latest Exchange Server updates and harden their environments to prevent malicious attacks.


Security researchers have observed an uptick in attacks targeting CVE-2021-35394, an RCE vulnerability in Realtek Jungle SDK.

Mobile & Wireless

Technical details published for an Arm Mali GPU flaw leading to arbitrary kernel code execution and root on Pixel 6.