Australia's New Payments Platform (NPP) processes 5.2 million real-time transactions per day under a 2,000 ms SLA. With cryptographically relevant quantum computers projected by 2030-2035 and the Harvest Now, Decrypt Later (HNDL) threat active, this paper presents a Monte Carlo simulation study of NIST FIPS 204/205/206 signature standards (ML-DSA, SLH-DSA/SPHINCS+, Falcon) in Australian payment infrastructure, jointly modelling M/M/c queue saturation, GEV tail bounds, and HNDL actuarial exposure across 1,000 seasonally-mixed simulation days (80 million events). Cross-platform validation used liboqs 0.15.0 on a seven-node multi-cloud testbed spanning four microarchitectures (Intel Xeon Ice Lake/Cascade Lake, AMD EPYC Milan, ARM Graviton3). ML-DSA and Falcon achieve 100% SLA compliance across all configurations; worst-case NPP p99 overhead is 1.57 ms (ML-DSA-87, 0.079% of SLA budget). We introduce the Crypto Dilution Index (CDI = delta-p99/p99_e2e), showing all non-SPHINCS+ algorithms achieve CDI < 0.04. GEV analysis yields p99.9 bounds below 154 ms (95% CI). Falcon-512 is the only NIST PQC signature fitting within the 2,048-byte SWIFT MT field limit (1,563 bytes combined). SPHINCS+ saturates HSM queues at NPP volumes (rho=1.8855, c=2 servers), achieving 0% NPP SLA compliance, characterised as a DoS amplification surface in hybrid deployments (utilisation ratio ~9,428x ECDSA). An HNDL actuarial model estimates 9.56 billion NPP records at risk under CRQC-2030. Migration costs peak at USD 21.4M in 2026, declining to USD 1.5M/year by 2028.

翻译：澳大利亚新支付平台（NPP）在2000毫秒服务等级协议（SLA）约束下日均处理520万笔实时交易。鉴于密码相关量子计算机预计于2030-2035年间出现，且“先存储后解密”（HNDL）威胁已然活跃，本文针对NIST FIPS 204/205/206签名标准（ML-DSA、SLH-DSA/SPHINCS+、Falcon）在澳大利亚支付基础设施中的应用开展蒙特卡洛模拟研究。研究联合建模了M/M/c队列饱和、广义极值（GEV）尾部边界及HNDL精算风险敞口，覆盖1000个季节性混合模拟日（8000万事件）。跨平台验证采用liboqs 0.15.0库，在横跨四种微架构（Intel Xeon Ice Lake/Cascade Lake、AMD EPYC Milan、ARM Graviton3）的七节点多云测试平台完成。ML-DSA与Falcon在所有配置下实现100% SLA合规率；NPP最差情况p99开销为1.57毫秒（ML-DSA-87，占SLA预算0.079%）。我们引入密码稀释指数（CDI=Δp99/p99端到端），表明所有非SPHINCS+算法均实现CDI<0.04。GEV分析给出p99.9边界低于154毫秒（95%置信区间）。Falcon-512是唯一符合2048字节SWIFT MT字段限制（合并后1563字节）的NIST后量子密码签名方案。SPHINCS+在NPP交易量下导致硬件安全模块（HSM）队列饱和（ρ=1.8855，c=2台服务器），实现0% NPP SLA合规率，被定性为混合部署中的拒绝服务放大面（利用率比约9428倍ECDSA）。HNDL精算模型预估在CRQC-2030情境下，956亿条NPP记录面临风险。迁移成本于2026年达峰值2140万美元，至2028年降至每年150万美元。