2025-08-05 –, Florentine A
Modern browsers implement sophisticated encryption to protect session cookies from theft, yet these security measures continue to evolve in response to emerging threats. This session reveals the inner workings of Chrome's recently implemented AppBound encryption, which employs a two-tier protection system: DPAPI encryption with dual permission levels and ChaCha20Poly1305 algorithm with custom keys.
Despite these advancements, vulnerabilities persist. Through practical demonstrations, we'll examine how determined attackers can extract decrypted cookies by exploiting weaknesses in the current implementation. The session provides a comprehensive analysis of cookie format specifications and encryption methodologies across major browser engines, including Gecko's ASN.1-structured encryption, macOS Chromium's PBKDF2 implementation, and WebKit's binary cookie storage.
Looking forward, we'll explore Chrome's upcoming "Device Bound Session Cookies" (DBSC) technology, which aims to revolutionize cookie protection through TPM chip-based encryption and cryptographic key verification. Attendees will gain actionable insights into current browser security architectures, practical extraction techniques, and defensive strategies to mitigate cookie theft. This technical deep-dive equips security professionals with the knowledge needed to better understand and address this persistent threat vector in modern web applications.
This session explores advanced security mechanisms implemented by major browsers to prevent cookie theft from their storage databases. Chrome has recently implemented AppBound encryption, which provides multi-layered protection for session cookies:
1) A 2-way DPAPI encryption system that operates with both elevated NT AUTHORITY\SYSTEM permissions and normal user-level decryption capabilities;
2) A state-key encryption layer utilizing the ChaCha20Poly1305 algorithm with custom keys (that once was AES-256-GCM encrypted);
These implementations have significantly reduced the effectiveness of info-stealing malware. However, this session will demonstrate potential vulnerabilities in these security measures and explain how to obtain decrypted cookies despite these protections. We will examine the new format specifications and encryption methodologies for cookies.
Beyond Chromium-based browsers, we'll explore Gecko's encryption algorithms, which involve structured ASN.1 data formats with multiple encryption schemes including 3DES and AES-256. We'll also analyze Chromium on macOS which relies on PBKDF2 key derivation, and WebKit-based browsers that store cookies in binary cookie files.
Additionally, we'll discuss Chrome's forthcoming "Device Bound Session Cookies" (DBSC) technology, which aims to further mitigate session hijacking through cookie theft by implementing TPM chip-based encryption and requiring proof of possession of the cryptographic key.
Rafael has been working with malware development for 4 years, also being involved in the malware community for more than 6 years. He is also experienced in Incident and Response, specifically during malware inner workings analysis. Currently, Rafael is a researcher for Hakai Offensive Security and Offensive Security Lead, being deeply involved with red-team operations.