A Zero-Trust Architecture · Prototype · 2026

Examination integrity,
guaranteed by
mathematics.

Every major exam paper leak in India traces to the same vulnerability: humans had access before the exam began. VAJRA makes that impossible — not through better policy, but through cryptography that no administrator, vendor, or insider can bypass.

Watch the Demonstration How It Works Full Walkthrough ↗
RSW · SHAMIR · X25519 · DRAND T → ∞ (UNTIL T=0)
01 — The Problem

A failure that
repeats itself.

India has the most rigorous high-stakes examination system in the world by sheer scale. It also has the most consistently breached. The pattern is the same every time: the paper exists in physical and digital form, in human hands, for hours or days before the exam begins. Every leak in the last decade has exploited that window.

1.51crore
applicants for ~1.2 lakh government posts have been affected by paper-leak incidents in 16 states over five years — across 48 documented breaches. Source: Indian Express investigation, cited in the legislative justification for the Public Examinations (Prevention of Unfair Means) Act, 2024. [1]
Confirmed 5 May 2024 NEET-UG · India
Conducted by NTA
24,06,079 candidates

The NEET-UG 2024 paper was stolen from an NTA storage trunk.

The CBI arrested an engineer who allegedly removed the question paper from a sealed trunk in Hazaribagh days before the exam. Brokers in Patna reportedly charged ₹30–50 lakh per candidate for advance copies, accommodating buyers in lodges to memorise answers overnight.[2]

The Supreme Court acknowledged the paper leak as an "undisputed fact" and that at least 155 candidates directly benefited, but declined to order a re-examination on the grounds that systemic failure could not be proven.[3] 67 students scored a perfect 720/720 that year — against an average of fewer than 2 in prior years.[4]

Vulnerability — physical custody before T=0.
Alleged 25 May 2025 UPSC CSE Prelims · India
Conducted by UPSC
Civil Services aspirants

UPSC Civil Services Prelims faced credible irregularity allegations.

Aspirants and a social activist publicly alleged paper-leak attempts and procedural failures including unsealed question paper packets distributed at exam centres — a "grave breach of standard security protocol." Reports flagged Rajkot as a distribution point where leaked papers were allegedly available for ₹30,000 the day before the exam.[5][6]

UPSC has historically maintained a strong record — the government informed Rajya Sabha that no leaks were officially reported in the two years preceding NEET 2024. But the structural vulnerability is identical: papers in physical custody, transported between humans, before T=0.[7]

Vulnerability — supply chain trust.
Investigated August 2024 SSC Clerical Exam · India
Conducted by SSC
Delhi-area centres

SSC identified an exact answer pattern across 53 candidates at 10 centres.

The Staff Selection Commission flagged 53 candidates who answered nearly every question correctly with what investigators described as an "exact pattern." Delhi Police registered an FIR and opened an investigation across 10 examination centres.[8]

This was not SSC's first such episode. In 2018, viral screenshots of the question paper with answers circulated on social media before the exam concluded, triggering nationwide protests outside the SSC office at Lodhi Road and a court-ordered CBI inquiry.[9]

Vulnerability — pre-exam content distribution.
Cancelled March 2024 BPSC Teacher Recruitment
Conducted by BPSC
5,00,000+ candidates

Bihar's teacher recruitment exam was cancelled mid-process after a confirmed leak.

The Bihar Public Service Commission cancelled its Teacher Recruitment Exam after question paper leak allegations were substantiated. Over five lakh candidates vying for 87,774 teaching positions were affected. The Economic Offences Unit arrested 285 people. The same season, the SSC Multi-Tasking Staff exam in Purnia and the Community Health Officer exam were both compromised by solver gangs.[10]

Vulnerability — insider access at every stage.
The Legislative Response

Parliament has tried to solve this with punishment. It cannot.

On 21 June 2024, the Public Examinations (Prevention of Unfair Means) Act, 2024 entered into force across all UPSC, SSC, NTA, RRB and banking recruitment examinations. Maximum penalties: 10 years' imprisonment, ₹1 crore fine. Maharashtra, Uttar Pradesh, and Arunachal Pradesh have since passed their own state laws with comparable provisions.[11][12]

Punitive law acts after a leak has destroyed an exam cycle and 24 lakh students' year. It deters some bad actors. It cannot prevent the breach from being possible in the first place. That requires changing what's physically possible — which is a cryptographic problem, not a legal one.

02 — The Architecture

Three independent locks.
No human shortcuts.

VAJRA encrypts the exam paper under three mathematically distinct constraints, each of which must independently be satisfied before decryption is possible. No single actor — not the administrator, not the testing agency, not any infrastructure vendor — can defeat all three. Every leak vector becomes either mathematically impossible or instantly attributable.

01

The Time LockRivest–Shamir–Wagner Puzzle

The exam is encrypted with a key that requires roughly T seconds of sequential CPU computation to recover. Provably sequential: no amount of parallelism, no supercomputer, no farm of GPUs can solve it faster. The administrator computes the key once, instantly, using a mathematical shortcut (the factorisation of a 1024-bit RSA modulus), encrypts the exam, and then destroys the shortcut.

From that moment, the only way to recover the decryption key is to start the squaring computation and wait. By the time it finishes, the exam has already begun. Even the administrator themselves cannot decrypt the paper early.

→ Defeats: early admin access · insider distribution · transport theft
02

The Consensus LockShamir's Secret Sharing · k-of-n

The decryption key is mathematically split into n pieces (one per regional centre). Any k centres can reconstruct the key by cooperating; k − 1 can reconstruct nothing — not by computational difficulty, but by information-theoretic impossibility. The pieces held by k − 1 centres contain literally no information about the key.

To leak the paper, an attacker would need to compromise at least k centres simultaneously. Not bribery of one official. Not theft of one trunk. Coordinated breach of a configurable threshold of independent organisations.

→ Defeats: single point of failure · bribery · isolated breach
03

The Addressed LockX25519 + ChaCha20-Poly1305 per centre

Each centre's piece of the key is further encrypted to that centre's specific X25519 public key before it ever leaves the source vault. The encrypted pieces are then published on a decentralised network (IPFS), but only the matching private key — held exclusively by that centre — can decrypt its assigned piece.

The administrator never sees a private key. The network is open and public; the pieces sitting on it are useless without coordinated cooperation. Centres need not even be online during the lock ceremony.

→ Defeats: network surveillance · server compromise · supply-chain interception
⧖

The Time Anchordrand Distributed Beacon

Independent of the three locks, VAJRA cryptographically binds each exam to a specific moment in publicly verifiable wall-clock time, using the drand beacon operated by Cloudflare, Protocol Labs, EPFL, and other members of the League of Entropy. The beacon emits a fresh signed random value every 30 seconds; the round corresponding to the exam start time cannot be predicted or forged before that moment.

Tampering with the target round — even by one second — invalidates decryption cryptographically. The system anchors against an external, neutral, publicly auditable source of time.

→ Defeats: clock manipulation · hardware variance attacks · post-hoc disputes
03 — The Ceremony

At T=0,
the locks fall away.

The reconstruction ceremony requires no human trust — only the presence and cooperation of k regional centres at the designated exam start time. No administrator is present. No vendor intermediates. The mathematics handles itself.

↑ The system unlocks a real exam paper, end to end, with no administrator present. The pause you see mid-clip is the time-lock doing its work — that minute cannot be shortcut.
Watch the full 9-minute walkthrough with narration →

  1. Each centre verifies the manifest.

    Cryptographic signature confirms the exam parameters have not been altered since lock-time.

  2. Each centre decrypts only their own piece.

    Using their private key, on their own machine. No other centre's data is ever visible.

  3. The drand beacon is consulted.

    The reconstruction refuses to proceed until the designated wall-clock round has provably published.

  4. k cooperating centres combine their pieces.

    Shamir's algorithm reconstructs the data key. With k − 1 pieces, the operation is information-theoretically impossible.

  5. The time-lock is solved.

    Sequential CPU work for exactly T seconds. No shortcut exists, even for the administrator.

  6. The exam paper appears.

    Decrypted, byte-identical to the original. Ready for printing or display.

04 — Honest Limitations

What this is, and what it isn't.

This is a working prototype. Every component described above is real, runs end-to-end, and is independently testable. The cryptographic primitives are well-known and well-audited. The system has been validated locking and unlocking real PDFs.

This is not a deployed product. VAJRA has not been used in any live examination. Production deployment would require larger cryptographic parameters (2048-bit RSA primes minimum), hardware-secured key custody at each centre, formal third-party security audit, integration with existing examination infrastructure, and a careful operational ceremony rehearsed with real examination boards.

We are not asking exam boards to use this tomorrow. The purpose of this work is to demonstrate that the cryptographic infrastructure for tamper-evident, leak-proof examination distribution exists, has been built, and is feasible at the scale of Indian high-stakes exams. The conversation we want to start is whether examination integrity should depend on procedural trust at all — when the mathematics to remove that dependency is now within reach.

05 — The Code

Open. Auditable.
Built to be broken.

VAJRA is open source. The Python orchestration layer, the Rust cryptographic core, and the full test suite are publicly hosted on GitHub. Cryptographic claims should be auditable by anyone with the relevant expertise.

Independent review is invited. If you can break what's claimed here, the claims will be retracted.

85 Passing tests
~3K Lines of code
4 Cryptographic primitives
0 External dependencies for crypto
View on GitHub
~/vajra bash
# Register 10 examination centres
$ python vajra_keygen.py bulk --n 10 --out-dir ./keys
✓ Generated 10 keypairs in keys/

# Admin locks an exam (60-second time-lock for testing)
$ curl -X POST localhost:8000/api/v1/lock \
-F "file=@exam.pdf" -F "exam_start_seconds=60"
✓ Manifest CID: bafy7q3...

# Each centre decrypts only their own piece
$ python vajra_center.py decrypt-share <cid> \
--my-key CENTER_003.json --out share_003.json

# Coordinator combines k pieces at T=0
$ python vajra_coordinator.py combine <cid> \
--share share_*.json --out exam.pdf
✓ Drand round verified · k=8 shares combined
✓ Time-lock solved in 60.02s
✓ exam.pdf recovered, 247 pages, MD5 matches.