CPU AES Decryption: Fact vs. Fiction

TL;DR

Recent claims about modern CPUs and their handling of AES decryption can be confusing. This guide explains what’s true, what’s not, and how to check your system. The core issue revolves around potential side-channel vulnerabilities in Intel processors, specifically related to the Advanced Encryption Standard (AES) instruction set. While these aren’t *new* problems, they are constantly being researched and mitigated.

Understanding the Claims

The main concerns centre on:

• Intel CPUs & AES-NI: Intel processors with AES-NI (Advanced Encryption Standard New Instructions) have dedicated hardware for faster encryption/decryption.
• Side-Channel Attacks: These attacks don’t break the AES algorithm itself, but exploit subtle variations in power consumption or timing during decryption to potentially reveal the key.
• Software Mitigations: Operating systems and software libraries are being updated with techniques to make these side-channel attacks harder to perform.

Step-by-Step Solution Guide

1. Check if your CPU has AES-NI support. This is the first step, as the vulnerabilities primarily affect CPUs *with* this hardware acceleration.
   • Linux: Use the lscpu command and look for a line that says “aes” under the Flags section:

     lscpu | grep aes

   • Windows: Open Command Prompt as administrator and run:

     wmic cpu get AESEnabled

     A value of TRUE indicates support.

2. Update your Operating System. Modern operating systems (Windows, macOS, Linux distributions) include mitigations for these vulnerabilities.
   • Windows: Ensure you have the latest Windows Updates installed via Settings > Update & Security > Windows Update.
   • macOS: Check for updates in System Preferences > Software Update.
   • Linux: Use your distribution’s package manager (e.g., sudo apt update && sudo apt upgrade on Debian/Ubuntu, or sudo yum update on Fedora/CentOS).
3. Update Software Libraries. Applications that use AES decryption rely on libraries like OpenSSL. Ensure these are up-to-date.
   • OpenSSL: The version of OpenSSL used depends on your OS and applications. Check the documentation for your specific software to see how to update it. For example, on Debian/Ubuntu:

     sudo apt update && sudo apt install --only-upgrade openssl

4. Consider Application-Specific Mitigations. Some applications (e.g., disk encryption tools like VeraCrypt) may have their own specific settings or updates to address these vulnerabilities.
   • Consult the application’s documentation for details.
5. Be aware of speculative execution risks. The side-channel attacks often exploit speculative execution, a performance optimization technique used by modern CPUs. While OS and software updates help mitigate this, it’s an ongoing area of research.
6. Check for Microcode Updates (Intel). Intel releases microcode updates that can address security issues in their processors.
   • Linux: The cpucheck tool can help verify if your system has the latest microcode:

     sudo apt install cpucheck && sudo cpucheck

   • Windows: Microcode updates are typically delivered through Windows Update.

What’s *Not* Likely to Be True

• Your data is immediately compromised: These attacks are complex and require specific conditions to be successful. Simply having an Intel CPU with AES-NI doesn’t mean your data is at risk.
• A simple software patch will completely eliminate the risk: Mitigations reduce the attack surface, but ongoing research means new vulnerabilities may emerge.

Resources

• Intel Security Updates: https://www.intel.com/content/www/us/en/security-center/
• OpenSSL Website: https://www.openssl.org/