Towards fully collusion-resistant ID-based establishment of pairwise keys.

Muxiang Zhang

圭介 田中, Keisuke Tanaka, 冬航 北川 +3 more

王莺洁, 潘军, 诸鸿文

Two ID-based authenticated group key agreement schemes, proposed by Choi et al and Du et al, are insecure against an impersonation attack and they only discussed the static group. This paper proposed a variant of BD protocol, which is fully authenticated by a proven-secure ID-based signature scheme. The protocol can resist the impersonation attack, and other security attributes are also satisfied. Compared with Choi et al and Du et al schemes, the proposed one is more efficient and applicable for dynamic groups.

Guohong Xie

Nikhil Pappu

It is well known that quantum computers, when fully realized, pose a threat to most cryptosystems deployed today. On the other hand, quantum information is also known to enhance classical cryptography, in terms of improved security and efficiency. Surprisingly, quantum information can also provide guarantees that are completely impossible to attain classically. The class of quantum cryptographic primitives called unclonable primitives fall into this category, with quantum money being a canonical example. Intuitively, quantum money allows a bank to distribute currency in the form of quantum states that provably resist counterfeiting due to the no-cloning theorem of quantum mechanics. This is in sharp contrast to classical information, for which there is no fundamental barrier that prevents its duplication. This work focusses on another up-and-coming unclonable primitive referred to as secure key leasing (SKL). This is a notion that allows to encode secret keys into a quantum state that can be temporarily leased. For example, it allows decryption keys of a public-key encryption scheme to be leased, enabling the recipient to decrypt ciphertexts while it possesses the quantum state. Later, the recipient can provide a proof of deletion which ensures that they have effectively ``lost'' access to the leased key. SKL is especially useful for software distributors that wish to provide trial period access. It allows them to provide access to their service via leased quantum keys, where they can incentivize timely deletion using a refund. In more detail, this dissertation studies SKL schemes in the setting of collusion, where multiple users can be leased independently generated quantum keys that provide access to the same underlying secret-key. It involves the study of meaningful notions of collusion-resistant security in this context, which are more realistic for real world applications than schemes secure in the standalone (single-key/single-user) setting. Then, new constructions are provided to realize these notions, with an emphasis on utilizing standard/well-understood cryptographic assumptions. Another major focus of the work is on providing modular approaches to constructing collusion-resistant SKL. In this light, novel compilers for different variants of the primitive are motivated and explored in detail.

Chien‐Ming Chen, Tsu‐Yang Wu