What happened has a witness.

Saakshi lives inside an ordinary calculator. When something happens, it silently records, encrypts every five seconds on her phone, and seals the evidence on a public blockchain, so anyone can check it.

Try the live app Verify a file

It’s a working calculator. Type 1931 then = to open Saakshi, or tap the display three times for a silent SOS. Duress PIN 0000.

Try it on your phone.
Scan to open this demo there, with the same PINs.

Why it matters

The thread running through all of it is proof.

Phones get snatched. Videos get deleted, or dismissed as edited. Saakshi makes sure the evidence survives the night and is believed in the morning.

77 of 100: women who face violence never tell anyone or seek help.; NFHS-5, 2019–21
4,48,211: crimes against women registered in 2023: over 1,200 a day.; NCRB, Crime in India 2023
1 in 5: cases of crime against women ended in conviction, 2017–2023.; NCRB data, The Wire
3.7%: conviction rate for crimes against women in West Bengal, 2023.; NCRB, Crime in India 2023

How it works

One night, five moments.

9:41 pm
It looks like a calculator. It is one.
Every key works. Its home-screen name and icon say Calculator, and so do the page title, browser storage and offline cache. Only her PIN followed by = opens Saakshi.
9:47 pm
Three taps. Nobody sees a thing.
She taps the display three times. The screen turns plum, then black. Camera, microphone and location keep recording while the screen stays awake and dark.
9:47:06 pm
Every five seconds, out of reach.
Each 5-second piece is fingerprinted with SHA-256 and encrypted with AES-GCM on her phone, then uploaded at once. Snatch the phone and you get, at most, the last five seconds.
9:52 pm
If he makes her stop, she can pretend.
A second, duress PIN makes it look as if recording stopped. It didn’t. It carries on, and the recording is flagged so she knows which night it was.
Next morning
Sealed. Shown. Checked.
Every piece was anchored on Polygon within a minute of being recorded. She shows the QR code, and anyone can check the file hasn’t changed by a single byte. No account, no trust in us required.

The vault: two sealed recordings, one stopped with the duress PIN

A sealed recording with its verify QR code

Proof, not promises

Anyone can check. Nobody has to trust us.

Drop a recording on the Verify page. Your browser fingerprints it, splits it back into the five-second pieces it was sealed as, checks each one’s Merkle proof, and reads the seal straight from the blockchain. Change a single byte and it says so.

A journal entry, as she sealed it. Change anything, even one letter.

Its SHA-256 is worked out in your browser as you type.

0 of 64 characters differ

0000000000000000000000000000000000000000000000000000000000000000

Saakshi seals the fingerprint, never the words. Anyone holding the file can work it out again and compare: the same file always gives the same 64 characters, and any change gives different ones.

recording-20261103-2045.webm

c2d9e85c … 4bee0453

Untampered

Recorded 3 Nov 2026, 8:45:55 pm IST. All 9 pieces sealed on Polygon Amoy, each within 69 s of being recorded. Block 51896446

recording-20261103-2045.webm, byte 8,70,558 changed

943ebfdd … 4f0d9772

No seal found

This file does not match any sealed fingerprint. If it is a copy of a file from Saakshi, it has been changed.

Our sample recording, and the same file with one byte changed. Check both yourself, or save its receipt and use the offline checker, which never talks to Saakshi.

Try it on the Verify page

evidence pieces sealed on Polygon

Merkle roots anchored on-chain

latest seal

Live from the EvidenceAnchor contract on Polygon Amoy, Polygon’s public test network.

More than a recorder

From the night itself to the complaint.

Sahayak, her rights in her language

Ask in Bengali, Hindi, English or eight more Indian languages, typed or spoken, and hear the answer read aloud. Answers cite only a fixed list of 27 sections and 8 helplines under BNS, BNSS, the DV Act, POSH, POCSO and the IT Act. Sahayak drafts the complaint for the police, a Protection Officer or the workplace committee, and the takedown request for the platform. Running on Gemma 4 through Adaption, with Sarvam behind it, it named a correct law for all 85 of our test questions, in 11 languages.

Guardians who know at once

Trusted people link through Telegram. When she starts an SOS they get her live location after a 10-second undo, at once if the duress PIN is used, and a warning if her phone goes silent. If her phone is lost or taken, two of them can let a new phone into her Saakshi; only her PIN opens it.

A journal and photos, sealed

Abuse is often a pattern, not one night. Dated diary entries and photos of injuries or messages are encrypted and sealed on Polygon like recordings.

A certificate for court

One tap prints the Section 63 certificate that the Bharatiya Sakshya Adhiniyam requires for electronic evidence: fingerprint, times, block and a QR code to verify. With a complaint from Sahayak, it prints as one packet, with where to get free legal help.

Under the hood

A snatched phone can record more. It can’t read what was recorded.

On her phone

An ECDH P-256 key pair; the private key is wrapped by her PIN (PBKDF2, 150,000 rounds).
Each SOS gets a fresh session key: ECDH + HKDF → AES-GCM-256.
Every 5-second piece is fingerprinted (SHA-256), then encrypted, before it leaves the phone.
An offline queue in IndexedDB retries the moment there’s signal.

On our servers

Only ciphertext, fingerprints and her wrapped key. We can’t watch a single second.
Row-level security on every table, and an append-only audit trail.
Anonymous accounts: no phone number, no email.
“Erase everything” removes her recordings, keys and account.

On Polygon

Each fingerprint is salted and gathered into a Merkle tree; only the root goes on-chain.
EvidenceAnchor.sol records each root for about 24,000 gas.
A relayer pays, so she never needs a wallet. A seal lands within about a minute.
A database job seals every minute, even after her phone is gone.

Contract: 0x39eA5AB65824af57297cE863CB54B1A84E3C4719. Its source code is verified on Sourcify as an exact match.

How we test it

Checked before it’s claimed.

We wrote 15 situations a woman might bring to Sahayak, and ask each in English, Bengali and Hindi, and five of them in eight more languages. A script checks every answer against the laws we listed for that situation. Gemma 4 answered 83 of the 85; Sarvam, its backup, answered two. Last run 1 Nov 2026.

85/85: questions where Sahayak named a correct law, answered in the language she asked in, and flagged danger when there was danger.
11/11: questions describing danger marked urgent, at least one in every language.
3.7 s: median time to an answer in English, Bengali and Hindi, on Gemma 4 through Adaption.
33: unit tests, among them the encryption, the Merkle proofs, the calculator and phone recovery. GitHub runs them, with type and lint checks, on every change.

Passed, by language

English
15/15
বাংলা
15/15
हिन्दी
15/15
मराठी
5/5
తెలుగు
5/5
தமிழ்
5/5
ગુજરાતી
5/5
ಕನ್ನಡ
5/5
മലയാളം
5/5
ଓଡ଼ିଆ
5/5
ਪੰਜਾਬੀ
5/5

Honest limits

What it can’t do, said plainly.

The screen stays on.: A web app can’t keep recording once the phone locks, so Saakshi holds the screen awake and black. A native Android app, our next step, would remove this.
A seal proves sameness, not truth.: It shows a file is unchanged since it was captured. It doesn’t prove what the file shows.
Test network, for now.: Seals go to Polygon Amoy during the hackathon. Moving to Polygon mainnet is a configuration change.
Information, not legal advice.: Sahayak explains which laws may apply and drafts the complaint; Saakshi drafts the Section 63 certificate. She signs them, and the police, a lawyer or a court decide what happens.

Questions

What people ask first.

Can Saakshi see her recordings?

No. Each piece is encrypted on her phone before it leaves, with a key only her PIN unlocks. Our servers hold scrambled data, fingerprints and a locked copy of her key. Nobody here can play a single second.

What if someone takes her phone?

They can stop the recording, not undo it. Every five seconds, what was recorded has already left the phone. Her guardians see her live location, and are told if the phone goes quiet.

What if someone knows her PIN?

Then they can open the vault, as she can. That is why there is a second PIN: typed under pressure, it looks like everything stopped, while recording carries on and her guardians are told she may not be able to talk.

Why does the app have such a plain address?

If someone checks her phone, they find a calculator and a forgettable address, web-alpha-orcin-85.vercel.app. Nothing that says she’s collecting evidence against them. Finding “Saakshi” in her browser history could put her in more danger, so the name lives only on this public site.

Does a seal prove what happened?

No. It proves the file hasn’t changed by a single byte since a moment fixed on Polygon. What the file shows is for the police and a court to weigh.

Will a court accept it?

Electronic records are admissible with a certificate under Section 63 of the Bharatiya Sakshya Adhiniyam, 2023. Saakshi fills one in from its seal records; she completes and signs it. Whether any evidence is accepted is for the court.

Does it work without internet?

Recording does. Pieces wait on the phone, encrypted, and upload the moment there is a signal. Sealing and guardian alerts need a connection.

Does it cost her anything?

No. She never needs a wallet or crypto: Saakshi pays for every seal. Sahayak and guardian alerts are free too.

Built during SHAKTI

Everything here started on 19 October.

19 Oct
The idea, the research and the Round 1 pitch.
20 Oct
Calculator disguise, silent SOS, encrypted 5-second capture, vault, duress PIN, undo, erase.
25 Oct
Shortlisted for the final. Evidence sealed on Polygon; the public Verify page; this site.
26 Oct
A sealed journal and photo vault, the Section 63 certificate, and Telegram guardian alerts with live location.
28–29 Oct
Sahayak: legal help, complaints and takedown requests in Bengali, Hindi and English, typed or spoken, on Gemma 4 through Adaption. Tested on 45 questions.
30–31 Oct
A sealed sample anyone can check on the Verify page. Moving to a new phone with her guardians’ approval. Sahayak reads its answers aloud.
1 Nov
Sahayak in eight more Indian languages. The court packet: her complaint, dated from her journal, with the evidence certificate. An offline checker that never talks to Saakshi.
2 Nov
Edge cases closed: an SOS cut off by a restart, browsers that can’t record, opening offline. The first Android build, disguised as a calculator.
NextPlanned
The Android app on real phones, so recording carries on with the screen locked.

Put it on a phone

It installs as a calculator.

Scan the code with an Android phone and open it in Chrome.
Choose ⋮ then “Add to Home screen”. It appears as “Calculator”.
Open it and set your own PIN. Nothing on the phone says Saakshi.

If someone checks her phone, they find a calculator and a forgettable address: web-alpha-orcin-85.vercel.app. Nothing that says she’s collecting evidence against them.

Scan to open the app