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Introduction

Every VeriSynth run produces a proof receipt — a small, cryptographically verifiable JSON file that records exactly how a synthetic dataset was generated. This proof enables reproducibility, auditability, and trust in the synthetic data lifecycle — without revealing the original data itself.

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Why Proofs Matter

When working with sensitive datasets (e.g. healthcare, finance, clinical trials), you need to prove that:
  • No real individuals were exposed
  • The data wasn’t tampered with
  • The synthetic results can be verified independently
Traditional anonymization or “black-box” synthetic data tools can’t provide this level of assurance. VeriSynth changes that by generating verifiable cryptographic receipts with every run.

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What’s in a Proof Receipt?

Each proof file (proof.json) contains key metadata about the synthesis process: 
{
  "verisynth_version": "core-0.1.0",
  "timestamp_utc": "2025-10-16T00:23:54Z",
  "input": {
    "path": "data/patients.csv",
    "rows": 10,
    "sha256": "05c493ca63a4...82b7",
    "merkle_root": "ddc322ce1f1d...a4c"
  },
  "output": {
    "path": "out/synthetic.csv",
    "rows": 1000000,
    "sha256": "c4452526fa8c...acb9",
    "merkle_root": "8045dd531825...c31"
  },
  "model": {
    "engine": "GaussianCopulaSynthesizer",
    "seed": 42,
    "metrics": {
      "corr_mean_abs_delta": 0.23,
      "naive_reid_risk": 0.0
    }
  },
  "proof": "merkle_root: 8045dd531825e51b8241d67732074492cad53fb415b8b393f556a7483eac8c31"
}

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Core Components

FieldDescription
verisynth_versionThe exact software version used for the run
timestamp_utcUTC time of generation
input / outputFile paths, row counts, SHA-256 hashes, and Merkle roots
modelModel type, seed, and fidelity metrics
proofFinal Merkle root representing dataset lineage

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1. File Hashing (SHA-256)

Each dataset (input and synthetic output) is hashed using SHA-256, producing a unique 64-character fingerprint. Example: 
sha256sum data/patients.csv
# → 05c493ca63a434a419da68828ec08eef23b997c94f7588ccdf5f8c5ac4ee82b7
Even a one-character change in the file alters the hash entirely. This ensures data integrity — you can confirm that the file used to create synthetic data hasn’t changed.

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2. Merkle Roots

VeriSynth combines all row-level hashes into a Merkle tree, creating a single compact fingerprint (Merkle root) representing the entire dataset. This allows independent verification without needing the full dataset.

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How it works

  1. Each record (row) is hashed individually.
  2. Pairs of hashes are combined and re-hashed up the tree.
  3. The final root hash represents the entire dataset’s integrity.
This approach is inspired by blockchain data structures — but runs fully offline.

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3. Statistical Metrics

Each proof includes quantitative fidelity and privacy diagnostics:
MetricMeaningGoal
corr_mean_abs_deltaAverage difference in correlation between real and synthetic dataLower = better realism
naive_reid_riskFraction of synthetic rows statistically too similar to any real recordLower = better privacy
(optional) ks_pvaluesKolmogorov–Smirnov similarity scores for numeric columnsHigher = better alignment
These values help users balance realism vs. privacy, and are logged for auditability.

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4. Deterministic Seeds

Each run uses a random seed that makes the entire synthesis process reproducible. Example: 
verisynth data/patients.csv -o out/ --rows 1000000 --seed 42
Re-running with the same seed, input, and model produces identical output and identical proof.json — a strong guarantee for regulated environments.

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5. Proof Verification (Coming Soon)

You’ll soon be able to verify proofs using: 
verisynth verify out/proof.json
This command will:
  • Re-hash your input and output files
  • Recompute Merkle roots
  • Compare against the proof receipt
  • Report if the dataset is unchanged and valid
Expected output: 
Verifying proof.json ...
✅ Merkle roots match
✅ Input/output hashes verified
✅ Metrics within tolerance

Result: VERIFIED (deterministic run)

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6. Reproducibility in Action

Try running VeriSynth twice with the same parameters: 
verisynth data/patients.csv -o out1/ --rows 1000 --seed 42
verisynth data/patients.csv -o out2/ --rows 1000 --seed 42
Then compare proofs: 
diff out1/proof.json out2/proof.json
If your proof system is working correctly, the files will be identical — down to the Merkle root.

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7. Future Extensions

Planned features for the proof system:
FeatureDescription
ed25519 signaturesAllow signed, verifiable proofs with public keys
ZK verification layerOptional zero-knowledge proof mode for third-party attestations
Diff privacy tracking (ε)Embed DP parameters directly in proofs
Remote proof viewerVisualize proofs via the VeriSynth web dashboard

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Summary

PrincipleDescription
IntegrityEvery dataset is hashed, verified, and traceable
ReproducibilitySame input + seed → identical proof
PrivacyNo real records retained or exposed
AuditabilityProof receipts can be independently verified offline