Abhishek S.
Shipping in public. Listening in private.

Abhishek

I lead women’s Indo-Western & Premium at Max Fashion. I also wrote the AI that runs the buying floor.

Rare profile. Category operator who ships production code.

Senior Buying Leader · Max Fashion Women’s Indo-Western & Premium · 530+ India stores NIFT ’12 · Twelve years on the floor

read the CV start a letter
abhishek@bengaluru ~ %
>role: senior buying lead
>dept: women’s indo-western + premium
>floor: 530+ stores india

Zero-Knowledge Alibi — Graduated-Disclosure Range Proofs for Criminal Defense

A zero-knowledge alibi is a cryptographic proof that a suspect was not at a crime scene location at the crime's time — without revealing where they actually were. The technology exists (2025); the legal framework does not.

The graduated-disclosure protocol is the key design insight: rather than proving an exact alibi location (which exposes privacy) or proving nothing (which provides no defense), range proofs progressively narrow the claimed geographic region until it provably excludes the crime scene location — without ever revealing the specific whereabouts.

Key Facts

How Graduated Disclosure Works

Step 1: Continuous Position Commitments

A suspect's phone (or any timestamped location device) generates cryptographic commitments to their H3 hexagonal grid cell at regular intervals throughout the day. The commitment is mathematically binding — it cannot be changed retroactively — but reveals nothing about the actual location. The suspect's device holds the private randomness needed to generate proofs from these commitments.

Step 2: Crime Event

A crime occurs at location L_crime at time T_crime.

Step 3: Graduated Proof Generation

Rather than revealing the alibi location, the defense generates a sequence of range proofs of progressively tighter geographic bounds:

  1. Coarse proof: "At time T_crime, I was within continent C" (essentially useless as alibi but establishes framework)
  2. Regional proof: "At time T_crime, I was within 500 km of coordinate X" (excludes regions)
  3. Exclusion proof: "At time T_crime, I was at least 120 km from L_crime" (the minimum necessary for alibi purposes, depending on jurisdiction and crime context)

The defense reveals only the tightest exclusion proof that demonstrates innocence, without revealing the actual location.

Why This Is Genuinely Novel

The key property: the proof is sound by mathematics, not trust. A traditional alibi requires witnesses or records that a third party must believe; a ZK alibi requires only that the cryptographic protocol is sound — no witness can be bribed, no record can be forged.

Three Unresolved Tensions

1. The Explainability Gap (most serious)

Courts in common-law traditions require that evidence be presented in a form human jurors can evaluate. A ZK range proof is human-inexplicable: it produces a binary result ("valid" / "invalid") from mathematics no layperson can audit. This is the concept chinese room at the institutional scale of justice: the court system processes proof-symbols it cannot understand, relying on expert testimony about whether the symbols are genuine.

This creates a structural legitimacy problem even before the evidence is deployed. Existing precedent for "black-box" expert evidence (DNA matching, forensic statistics) shows courts can accept non-intuitive probabilistic evidence — but those methods generate human-interpretable numbers (match probabilities). A ZK proof generates only soundness guarantees that themselves require cryptographic expertise to verify.

Gap: no legal framework specifies the minimum threshold of jury comprehensibility for ZK-based evidence.

2. The Trusted Data Custodian Problem

A ZK alibi is only sound if the position commitments were honestly generated at the claimed times. This requires an unbroken chain:

The mathematics of the ZK proof only works if this custody chain is honest. Who acts as the trusted position oracle in a criminal proceeding? The defendant's own device is untrustworthy; a court-appointed agent must be involved continuously — a logistical impossibility if location-proofing wasn't established before the crime.

Gap: the institutional infrastructure for continuous, court-trusted position commitments does not exist in any jurisdiction.

3. The Geographic Resolution Question

Different legal jurisdictions define alibi differently. An alibi in English law typically means "I was at a different place"; in some US federal contexts, the alibi must be specific enough to be falsifiable. The minimum geographic resolution that satisfies "beyond reasonable doubt" for alibi purposes varies by:

A Bulletproof range proof can prove "I was more than R km from the crime scene" for any R — but what R is legally sufficient has never been defined by any court.

The Retroactivity Problem

The most fundamental limitation: position commitments cannot be made retroactively. A suspect who did not establish a continuous timestamped commitment chain before the crime cannot later prove a ZK alibi for that time. This is structurally identical to the concept naibbe key problem: the key that would enable decryption (the position commitment chain) is not missing because it was hidden, but because it was never created — it is thermodynamically irretrievable not because it was lost, but because it never existed.

This creates an asymmetry: the technology is most useful when established prospectively as a continuous privacy-preserving location journal, which requires individuals to opt into continuous monitoring before any crime occurs — a significant behavioral and ethical ask.

Cross-Realm Connections

Current Status (2026)

The ZK alibi is a case where the cryptography is finished and the institutions have not started.

See Also