Onion-Routed Multi-Circuit Key Establishment for Quantum-Resilient Sessions

Computer Science > Cryptography and Security [Submitted on 20 May 2026] Onion-Routed Multi-Circuit Key Establishment for Quantum-Resilient Sessions Tushin Mallick, Ashish Kundu, Ramana Kompella Public-key primitives that today anchor session-key establishment - RSA, Diffie-Hellman, and elliptic-curve cryptography - reduce to integer factorization or discrete logarithm and are therefore vulnerable to Shor's algorithm on a sufficiently capable quantum computer. The harvest-now, decrypt-later (HNDL) threat model turns this future capability into a present liability: ciphertext archived today can be decrypted retrospectively once a cryptographically relevant quantum computer becomes available. We propose a session-key establishment scheme that distributes a freshly generated key as multiple, independently encrypted fragments across distinct, ephemeral Tor circuits between an onion-service proxy and an onion-service client. Reconstruction requires every fragment; each fragment travels its own per-bundle circuit established via a NEWNYM signal. The security argument rests on the standard end-to-end correlation bound for onion routing: an adversary controlling a fraction of Tor relays must independently deanonymize every fresh circuit to correlate the fragments belonging to one session, and the per-fragment probability of success decays multiplicatively in the number of fragments. We implement the design as a Flask-based prototype on AWS EC2, with both the proxy and the client deployed as Tor onion services, and measure end-to-end key-establishment latency. The implemented prototype completes a key establishment in 13-20 s on average (7-50 s including tails), of which approximately 88% is attributable to Tor-related delay - a cost we discuss in the context of the privacy-versus-responsiveness trade-off. Subjects: Cryptography and Security (cs.CR) Cite as: arXiv:2605.21349 [cs.CR]   (or arXiv:2605.21349v1 [cs.CR] for this version)   https://doi.org/10.48550/arXiv.2605.21349 Focus to learn more Submission history From: Tushin Mallick [view email] [v1] Wed, 20 May 2026 16:14:07 UTC (315 KB) Access Paper: HTML (experimental) view license Current browse context: cs.CR < prev   |   next > new | recent | 2026-05 Change to browse by: cs References & Citations NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)