Google has unveiled significant network security enhancements in Android 17, aimed at improving user privacy by introducing the Encrypted Client Hello (ECH) standard. ECH is designed to protect users by preventing network providers from discerning which websites they are visiting. This is achieved by encrypting the domain names at the start of the connection, thereby obscuring metadata that could be used for profiling. According to Google's Bram Bonné and Shuaibo Huang, ECH works alongside private DNS to further secure user data.
Google's Jigsaw division elaborated that ECH uses a secret encryption key, decipherable only by the destination website, to hide domain names. However, not all web servers support ECH, which led to the implementation of ECH GREASE in Android 17. This feature sends randomized ECH extensions to non-supporting sites, ensuring uniformity in connection requests. ECH GREASE will be enabled by default across the operating system, expanding the protection beyond browsers like Google Chrome and Mozilla Firefox, which recently integrated ECH in their latest versions.
Additionally, Google's OkHttp library now includes ECH support, empowering third-party developers to incorporate this privacy feature into their apps. Android 17 also introduces Local Network Protection, requiring apps to obtain user permission before accessing local network devices. Further security measures include enabling Certificate Transparency by default to ensure websites are logged publicly and allowing telecom operators to disable 2G by default. This move mitigates the risk of downgrade attacks and exposure to rogue base stations or SMS blasters, providing a proactive defense against potential threats.