面向中小企业云数据保护的混合后量子加密架构，具备自托管密钥管理功能
A Hybrid Post-Quantum Encryption Architecture with Self-Hosted Key Management for SME Cloud Data Protection
AI总结：
针对中小企业云数据的后量子安全需求，提出Quantum Cloud Guard三层架构，实现混合后量子加密、自托管密钥管理与滥用防护，验证了性能与防护效果。
AI中文摘要：
从云存储中获取密文无需量子计算机，但后续解密需要量子计算机，这一“先获取后解密”的时间差带来了安全隐患：当前使用RSA或ECDH保护且需保密数十年的信息已面临风险。中小企业应对能力最弱：它们既不掌控存储数据的基础设施，也未配备密码学家。定制化迁移适合有安全预算的企业；托管密钥服务虽能转移信任却无法消除信任。问题的症结在于架构层面，而非密码学本身。我们提出Quantum Cloud Guard（QCG），这是一种纯软件的三层架构。此前没有任何面向中小企业的系统同时具备以下三个要素：客户端混合后量子加密、自托管密钥保管（对服务密钥采用客户端可验证的ML-DSA-87签名），以及集成的应用层滥用防护网关。文件永远不会离开客户端：每个文件都用AES-256-GCM加密，其密钥被封装到企业密钥服务的ML-KEM-1024公钥中。仅由企业管理该服务；企业用ML-DSA-87对每个密钥签名，因此固定了该签名的客户端可检测密钥替换。将密钥保管与数据保管分离是核心目的：同时持有两者的服务提供商可读取数据。在24 MHz的STM32F407上，ML-KEM-1024密钥生成耗时40.8毫秒，解封装耗时44.0毫秒；在服务器端，所有后量子操作均在1毫秒内完成，签名操作每请求增加0.24毫秒。该服务运行在每月4.49欧元的虚拟服务器上。在持续泛洪测试中，进程内网关Sentinel Gate拒绝了98.8%的攻击流量，而合法客户端的中位延迟从621毫秒变为625毫秒。由于是单源部署，该结果仅体现过滤效果，而非DDoS抗御能力。
英文摘要：
Harvesting ciphertext from cloud storage needs no quantum computer; decrypting it later does. That gap is the harvest-now-decrypt-later exposure: anything protected by RSA or ECDH today that must stay secret for decades is already compromised. Small and medium-sized enterprises are least able to respond: they neither run the infrastructure on which their data sits on nor employ a cryptographer. Bespoke migration suits firms with security budgets; a managed key service relocates trust rather than removing it. The obstacle is architectural, not cryptographic. We present Quantum Cloud Guard (QCG), a software-only three-layer architecture. No prior SME-oriented system combines its three elements: client-side hybrid post-quantum encryption, self-hosted key custody with client-verifiable ML-DSA-87 signatures on served keys, and an integrated application-layer abuse-prevention gateway. Files never leave the client: each is sealed under AES-256-GCM, its key wrapped to an ML-KEM-1024 public key from the enterprise's key service. The enterprise alone administers it; it signs every key with ML-DSA-87, so a client that pinned it detects substitution. Separating key custody from data custody is the point: a provider holding both can read the data. On a 24 MHz STM32F407, ML-KEM-1024 key generation takes 40.8 ms and decapsulation 44.0 ms; on the server every post-quantum operation stays sub-millisecond, signing adding 0.24 ms per request. The service runs on a 4.49 EUR/month virtual server. Under sustained flooding, the in-process gateway Sentinel Gate rejected 98.8% of attack traffic while a legitimate client's median latency moved from 621 to 625 ms. Being single-source, this shows filtering effectiveness, not DDoS resilience.
