-
-
Architecture
-
Quantum Walk Distribution
-
Blockchain verification
-
Blockchain
Inspiration
India processes over 17 billion UPI transactions annually, all protected by SHA-256, a hash function from 2001. However, NIST confirmed in 2024 that quantum computers running Grover’s Algorithm will halve SHA-256’s security. Despite the quantum threat and its imminent impact, no one is building a replacement today. We found a mathematical approach that runs on normal computers but resists quantum attacks.
What it does
QuantumPay, a quantum-safe payment integrity system, replaces SHA-256 with a Quantum Hash Function (QHF) built from Controlled Alternate Quantum Walks (CAQW). It comprises four components: the Send Payment tab creates a UPI-style payment by converting data to binary, simulating a quantum walk on an 8x8 grid, and generating a 512-bit quantum fingerprint; the Payment Ledger displays a live blockchain with QHF links instead of SHA-256; the QHF Explorer generates hashes, runs an avalanche test showing a bit change alters ~45% of the hash output, and compares QHF to SHA-256.
How we built it
The backend uses FastAPI and numpy for quantum walk linear algebra, implementing the CAQW simulation from the Abd El-Latif et al. paper. The frontend is simple HTML, JavaScript, and CSS, and the entire project runs locally.
Challenges we ran into
The most difficult challenge was implementing the quantum walk, requiring a deep understanding of CAQW mathematics and numpy matrix operations. The second challenge was maintaining focus on QHF-based payment integrity, avoiding the temptation to add unrelated features.
Accomplishments that we're proud of
We implemented actual CAQW linear algebra running live on every hash request. The avalanche test returns genuine computed results: 232 bits changed out of 512 on a one-bit input flip, matching the paper's Figure 4 which shows 893 out of 1800 bits changing for N=15. The attack simulation catches payment tampering through actual hash re-computation.
What's next for QuantumPay
The longer-term vision is integrating with India's UPI sandbox API so real payment flows can be protected, and benchmarking the quantum walk computation on cloud infrastructure to establish realistic latency numbers for production consideration. The NPCI and RBI have both published papers on CBDC and digital payment security — QuantumPay's architecture is directly relevant to that conversation.
Log in or sign up for Devpost to join the conversation.