ABSTRACT Quantum identity authentication (QIA) can provide quantum‐interface evidence for quantum secure communication, but its interaction with public transcript handling remains insufficiently characterized. This work analyzes a raw‐feedback QIA interface based on BB84 states and operating over an authenticated classical channel, where transcript integrity is protected but receiver feedback is public. First, we establish a no‐feedback benchmark: direct impersonation reduces to binary discrimination of value‐conditioned BB84 mixed states, for which unambiguous state discrimination is impossible and maximum‐confidence discrimination gives no forced‐response advantage over minimum‐error discrimination. Second, we identify a transcript‐conditioned leakage mechanism: when an adversary retains a quantum auxiliary system, public raw feedback can condition that system into a pure‐state discrimination instance for basis‐selection information. We quantify this leakage using guessing probability, conditional min‐entropy, accessible information, and an information‐disturbance tradeoff. Third, we separate leakage from exploitation: the leakage becomes an impersonation advantage only under implementation deviations such as key‐block reuse, weak session binding, abort‐handling failure, or overly permissive thresholds. These results yield conservative authentication‐length and threshold conditions for noisy and lossy optical implementations.
This paper presents an autonomous perfectly secure low-bit-rate voice communication system (APS-VCS) based on the mixed-excitation linear prediction voice coder (MELPe), Vernam cipher, and sequential key distillation (SKD) protocol by public discussion. An authenticated public channel can be selected in a wide range, from internet connections to specially leased radio channels. We found the source of common randomness between the locally synthesized speech signal at the transmitter and the reconstructed speech signal at the receiver side. To avoid information leakage about open input speech, the SKD protocol is not executed on the actual transmitted speech signal but on artificially synthesized speech obtained by random selection of the linear spectral pairs (LSP) parameters of the speech production model. Experimental verification of the proposed system was performed on the Vlatacom Personal Crypto Platform for Voice encryption (vPCP-V). Empirical measurements show that with an adequate selection of system parameters for voice transmission of 1.2 kb/s, a secret key rate (KR) of up to 8.8 kb/s can be achieved, with a negligible leakage rate (LR) and bit error rate (BER) of order 10−3 for various communications channels, including GSM 3G and GSM VoLTE networks. At the same time, by ensuring perfect secrecy within symmetric encryption systems, it further highlights the importance of the symmetry principle in the field of information-theoretic security. To our knowledge, this is the first autonomous, perfectly secret system for low-bit-rate voice communication that does not require explicit prior generation and distribution of secret keys.
We present a modular hierarchy of private delegated quantum computation protocols tailored to user-level and industry-level settings and parameterized by the quantum resources available to the client. For each protocol, we specify the client capabilities, delegated gate set, adversarial model, transcript leakage and resulting privacy claims. The hierarchy separates QOTP state privacy under declared leakage from leakage-dependent transcript-level angle ambiguity, compiler- and leakage-function-dependent structural privacy, and output privacy, clarifies when public Clifford operations can be evaluated on quantum-one-time-pad encrypted data by classical key updates, and identifies where non-Clifford privacy, non-collusion or additional primitives are required. The classical-client branch uses a persistent common-node, matching-hidden split-QOTP together with shuffled finite-grid
r-share sign-randomized angle sharing to obtain leakage-relative state hiding under an explicit
εkey key-hiding condition and transcript-level unlinkability under hidden-matching assumptions under an explicit non-total-collusion and leakage model. The angle-sharing primitives provide transcript ambiguity under explicit leakage assumptions, not universal blindness. The trap-based layer provides detection under stated assumptions, but it is not a stand-alone malicious-security proof.