# Document Verification

Learn how to verify the authenticity of signed documents.

## What is Verification?

Verification proves that:

* Document hasn't been tampered with
* Signatures are authentic
* Timestamps are accurate
* Signers are who they claim to be

## How to Verify

### Method 1: Via CapSign App

1. Navigate to **Documents** → **Verify**
2. Upload document or enter content hash
3. View verification results:
   * All signatures
   * Signer addresses
   * Timestamps
   * Attestation details

### Method 2: Via EAS Explorer

1. Get attestation UID from document
2. Visit [EAS Explorer](https://base.easscan.org)
3. Enter attestation UID
4. View full attestation details

### Method 3: Via Smart Contract

Query the EAS contract directly:

```solidity
function getAttestation(bytes32 uid) external view returns (Attestation memory);
```

## What Verification Shows

### Document Integrity

**Content Hash:**

* Compare calculated hash with on-chain hash
* If they match, document is unaltered

**Storage URI:**

* Link to original document
* Verify document is accessible

### Signature Authenticity

**Signer Address:**

* Wallet address that signed
* Verify it's the expected signer

**Timestamp:**

* When document was signed
* Blockchain timestamp (immutable)

**Transaction:**

* On-chain transaction proof
* View on block explorer

## Verification Results

### ✅ Valid

* Content hash matches
* Signature authentic
* Timestamp verified
* All signers confirmed

### ⚠️ Warning

* Content hash mismatch (document altered)
* Missing signatures
* Revoked attestation

### ❌ Invalid

* Attestation not found
* Signature verification failed
* Fraudulent document

## Use Cases

### Legal Proceedings

Provide evidence:

* Document content
* Signature attestations
* Blockchain transactions
* Timestamp proofs

### Compliance Audits

Demonstrate:

* Document signed by all parties
* Signed on specific dates
* No alterations after signing

### Due Diligence

Verify:

* Investment documents authentic
* Proper signatures obtained
* Legal requirements met

## Best Practices

* **Always verify** documents before relying on them
* **Check all signers** - ensure all required parties signed
* **Compare hashes** - document content matches attestation
* **Check timestamps** - signatures made when expected
* **Save verification results** for your records

## Technical Details

### Content Hashing

CapSign uses SHA-256:

```
sha256(document_bytes) = content_hash
```

Compare this hash with on-chain hash to verify integrity.

### Attestation Structure

EAS attestations contain:

* Schema UID (document schema)
* Recipient (signer address)
* Attester (document creator)
* Data (content hash, URI, metadata)
* Timestamp
* Expiration (if any)
* Revocation status

## FAQs

**Q: Can verification be faked?** A: No. Blockchain verification is cryptographically secure.

**Q: What if document was altered after signing?** A: Hash won't match, verification will fail.

**Q: Can I verify without CapSign?** A: Yes, directly via EAS or blockchain explorers.

**Q: What if attestation is revoked?** A: Verification will show "Revoked" status and reason.

## See Also

* [Uploading Documents](/capsign/documents/uploading-documents.md)
* [Signing Documents](/capsign/documents/signing-documents.md)
* [EAS Documentation](https://docs.attest.sh)


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