Conference paper Open Access

Subverting Decryption in AEAD

Armour, M.; Poettering, B.

This work introduces a new class of Algorithm Substitution Attack (ASA) on Symmetric Encryption Schemes. ASAs were introduced by Bellare, Paterson and Rogaway in light of revelations concerning mass surveillance. An ASA replaces an encryption scheme with a subverted version that aims to reveal information to an adversary engaged in mass surveillance, while remaining undetected by users. Previous work posited that a particular class of AEAD scheme (satisfying certain correctness and uniqueness properties) is resilient against subversion. Many if not all real-world constructions – such as GCM, CCM and OCB – are members of this class. Our results stand in opposition to those prior results. We present a potent ASA that generically applies to any AEAD scheme, is undetectable in all previous frameworks and which achieves successful exfiltration of user keys. We give even more efficient non-generic attacks against a selection of AEAD implementations that are most used in practice. In contrast to prior work, our new class of attack targets the decryption algorithm rather than encryption. We argue that this attack represents an attractive opportunity for a mass surveillance adversary. Our work serves to refine the ASA model and contributes to a series of papers that raises awareness and understanding about what is possible with ASAs.

Files (657.4 kB)
Name Size
28-Subverting Decryption in AEAD.pdf
md5:ec188bc99e7ec227085c8a871392f41b
657.4 kB Download
30
13
views
downloads
All versions This version
Views 3030
Downloads 1313
Data volume 8.5 MB8.5 MB
Unique views 2727
Unique downloads 1313

Share

Cite as