# WIA Digital Time Capsule Standard - Technical Specification

**Standard ID:** WIA-LEG-001
**Version:** 1.0
**Status:** Production Ready
**Date:** January 2025
**Category:** Legacy & Digital Heritage

---

## Abstract

The WIA Digital Time Capsule Standard (WIA-LEG-001) defines a comprehensive framework for creating, storing, and accessing digital time capsules—sealed collections of digital content intended for future retrieval. This specification addresses the unique challenges of long-term digital preservation including format obsolescence, data integrity, access control, and cryptographic security.

## 1. Introduction

### 1.1 Purpose

This standard provides:
- Standardized container format for digital time capsules
- Cryptographic protocols for sealing and verification
- Time-based access control mechanisms
- Format migration strategies for long-term preservation
- API specifications for programmatic access

### 1.2 Scope

The standard covers:
- Data format specifications (WIA-TC format)
- Security and encryption protocols
- Access control and time-locking mechanisms
- Storage backend integration
- API and SDK interfaces

### 1.3 Terminology

- **Time Capsule**: A sealed collection of digital content with time-based access restrictions
- **Sealing**: The process of finalizing, encrypting, and signing a time capsule
- **Unlock Date**: The predetermined date when a time capsule becomes accessible
- **Capsule ID**: Unique identifier for each time capsule
- **Content Hash**: Cryptographic hash of capsule contents for integrity verification

## 2. Architecture

### 2.1 Four-Layer Model

```
┌─────────────────────────────────────────┐
│      Integration Layer                  │
│  (Blockchain, IPFS, Cloud Storage)      │
├─────────────────────────────────────────┤
│      Security Layer                     │
│  (Encryption, Signing, Access Control)  │
├─────────────────────────────────────────┤
│      API Layer                          │
│  (REST, TypeScript SDK, CLI)            │
├─────────────────────────────────────────┤
│      Data Format Layer                  │
│  (WIA-TC Container Format)              │
└─────────────────────────────────────────┘
```

### 2.2 Component Interaction

```
Client Application
    ↓
TypeScript SDK / REST API
    ↓
Security Module (Encryption/Signing)
    ↓
Storage Adapter (IPFS/S3/Blockchain)
    ↓
Distributed Storage
```

## 3. Data Format Specification

### 3.1 WIA-TC Container Format

The WIA-TC format consists of:

```json
{
  "version": "1.0",
  "metadata": {
    "id": "TC-YYYY-NNN-XXX",
    "title": "string",
    "description": "string",
    "created": "ISO8601 timestamp",
    "creator": {
      "name": "string",
      "email": "string",
      "publicKey": "base64 encoded public key"
    },
    "unlockDate": "ISO8601 timestamp",
    "status": "draft|sealed|unlocked"
  },
  "security": {
    "encrypted": true,
    "algorithm": "AES-256-GCM",
    "signature": {
      "algorithm": "Ed25519",
      "publicKey": "base64",
      "signature": "base64"
    },
    "contentHash": "SHA3-256 hash"
  },
  "access": {
    "earlyAccess": {
      "enabled": false,
      "requiresApproval": true,
      "approvers": ["email@example.com"]
    },
    "multiParty": {
      "required": false,
      "threshold": 2,
      "totalParties": 4
    }
  },
  "contents": [
    {
      "id": "content-001",
      "filename": "string",
      "type": "image|video|document|audio|other",
      "size": 1234567,
      "format": "jpg|mp4|pdf|...",
      "checksum": "SHA3-256 hash",
      "metadata": {
        "description": "string",
        "tags": ["tag1", "tag2"],
        "created": "ISO8601 timestamp"
      },
      "encrypted": true,
      "encryptedData": "base64 encoded"
    }
  ],
  "storage": {
    "primary": {
      "type": "ipfs|s3|azure|gcs",
      "location": "URI or hash",
      "timestamp": "ISO8601"
    },
    "backups": [
      {
        "type": "storage type",
        "location": "URI",
        "timestamp": "ISO8601"
      }
    ]
  },
  "blockchain": {
    "network": "ethereum|polygon|...",
    "transactionHash": "0x...",
    "blockNumber": 12345,
    "timestamp": "ISO8601"
  }
}
```

### 3.2 File Structure

```
capsule-root/
├── manifest.json          # Metadata and index
├── contents/              # Encrypted content files
│   ├── content-001.enc
│   ├── content-002.enc
│   └── ...
├── signatures/            # Digital signatures
│   ├── manifest.sig
│   └── contents.sig
└── keys/                  # Encrypted key material
    └── master.key.enc
```

## 4. Security Protocols

### 4.1 Encryption

**Algorithm:** AES-256-GCM (Galois/Counter Mode)

**Process:**
1. Generate random 256-bit encryption key
2. Generate random 96-bit IV (Initialization Vector)
3. Encrypt content using AES-256-GCM
4. Store authentication tag with encrypted data
5. Encrypt master key using public key cryptography

### 4.2 Digital Signatures

**Algorithm:** Ed25519 (EdDSA)

**Process:**
1. Generate Ed25519 key pair for creator
2. Calculate SHA3-256 hash of capsule contents
3. Sign hash with private key
4. Store public key and signature in manifest
5. Verification: Validate signature using public key

### 4.3 Time-Lock Cryptography

**Mechanism:** Time-based key release

```
Master Key → Time-Lock Puzzle → Released at Unlock Date
```

**Implementation:**
- Use time-lock encryption with sequential work requirement
- Store encrypted key shards with trusted time servers
- Release key material only after unlock date

### 4.4 Multi-Party Authorization

**Threshold Scheme:** Shamir's Secret Sharing

```
Master Key → Split into N shares → Require M shares to reconstruct
```

**Example:** 3-of-5 scheme
- Master key split into 5 shares
- Any 3 shares can reconstruct the key
- Distributed to 5 authorized parties

## 5. Access Control

### 5.1 Time-Based Access

```typescript
interface TimeBasedAccess {
  unlockDate: Date;
  timezone: string;
  automaticUnlock: boolean;
}
```

**Rules:**
- Capsule is sealed and inaccessible before unlock date
- Automatic unlock at specified date/time
- Timezone-aware unlock scheduling

### 5.2 Early Access

```typescript
interface EarlyAccess {
  enabled: boolean;
  requiresApproval: boolean;
  approvers: string[];
  reason?: string;
  auditLog: boolean;
}
```

**Process:**
1. User requests early access
2. Request sent to all approvers
3. M-of-N approvers must approve
4. All actions logged in audit trail
5. Temporary access granted with expiration

### 5.3 Permission Levels

```
Owner        → Full control (cannot modify after sealing)
Approver     → Can approve early access requests
Viewer       → Read-only access after unlock
Public       → Limited metadata visibility
```

## 6. API Specification

### 6.1 RESTful API

**Base URL:** `https://api.wia.org/timecapsule/v1`

#### Create Time Capsule

```http
POST /capsules
Content-Type: application/json
Authorization: Bearer {token}

{
  "title": "Family Memories 2025",
  "description": "...",
  "unlockDate": "2050-01-01T00:00:00Z",
  "encryption": {
    "enabled": true,
    "algorithm": "AES-256-GCM"
  }
}

Response: 201 Created
{
  "id": "TC-2025-001-XYZ",
  "status": "draft",
  "created": "2025-01-15T10:30:00Z"
}
```

#### Add Content

```http
POST /capsules/{id}/contents
Content-Type: multipart/form-data

file: [binary data]
metadata: {
  "type": "image",
  "description": "Family reunion photo"
}

Response: 201 Created
{
  "contentId": "content-001",
  "checksum": "sha3-256-hash",
  "size": 2457600
}
```

#### Seal Capsule

```http
POST /capsules/{id}/seal
Content-Type: application/json

{
  "signature": true,
  "blockchain": true,
  "storage": ["ipfs", "s3"]
}

Response: 200 OK
{
  "status": "sealed",
  "ipfsHash": "QmX7Y8Z...",
  "blockchainTx": "0xabc123...",
  "unlockDate": "2050-01-01T00:00:00Z"
}
```

#### Get Capsule Status

```http
GET /capsules/{id}
Authorization: Bearer {token}

Response: 200 OK
{
  "id": "TC-2025-001-XYZ",
  "title": "Family Memories 2025",
  "status": "sealed",
  "unlockDate": "2050-01-01T00:00:00Z",
  "daysUntilUnlock": 9131,
  "contentCount": 3,
  "totalSize": 47612928
}
```

### 6.2 TypeScript SDK

See `/api/typescript/` for complete SDK implementation.

```typescript
import { TimeCapsuleSDK } from '@wia/digital-time-capsule';

const sdk = new TimeCapsuleSDK({ apiKey: '...' });

const capsule = await sdk.create({
  title: 'My Time Capsule',
  unlockDate: new Date('2050-01-01')
});

await capsule.addFile('./photo.jpg');
await capsule.seal();
```

## 7. Storage Integration

### 7.1 IPFS (InterPlanetary File System)

**Advantages:**
- Content-addressed storage
- Decentralized and resilient
- Immutable content hashes

**Implementation:**
```javascript
const ipfsHash = await ipfs.add(capsuleData);
// Returns: QmX7Y8Z9A1B2C3D4E5F6G7H8I9J0K...
```

### 7.2 Blockchain Timestamping

**Purpose:** Immutable proof of existence

**Process:**
1. Calculate SHA3-256 hash of sealed capsule
2. Submit hash to blockchain (Ethereum/Polygon)
3. Store transaction hash and block number
4. Provides verifiable timestamp

### 7.3 Cloud Storage

**Supported Providers:**
- Amazon S3
- Google Cloud Storage
- Microsoft Azure Blob
- Custom S3-compatible endpoints

**Configuration:**
```json
{
  "type": "s3",
  "bucket": "wia-capsules",
  "region": "us-east-1",
  "encryption": "AES256",
  "versioning": true
}
```

## 8. Format Migration

### 8.1 Migration Policy

```typescript
interface MigrationPolicy {
  enabled: boolean;
  checkInterval: 'yearly' | 'monthly';
  rules: MigrationRule[];
}

interface MigrationRule {
  sourceFormat: string;
  targetFormat: string;
  preserveOriginal: boolean;
  quality: 'lossless' | 'high' | 'medium';
  triggers: {
    formatDeprecated: boolean;
    betterFormatAvailable: boolean;
  };
}
```

### 8.2 Supported Migrations

| Source Format | Target Format | Strategy |
|--------------|---------------|----------|
| DOCX         | PDF/A         | Convert to archival PDF |
| MP4 (H.264)  | AV1           | Re-encode to modern codec |
| JPEG         | AVIF/WebP     | Modern image format |
| PNG          | PNG (optimized)| Lossless optimization |
| WAV          | FLAC          | Lossless compression |

## 9. Security Considerations

### 9.1 Threat Model

**Threats:**
- Unauthorized access before unlock date
- Content tampering or modification
- Key compromise
- Storage provider compromise
- Format obsolescence

**Mitigations:**
- Strong encryption (AES-256-GCM)
- Digital signatures (Ed25519)
- Multi-party authorization
- Distributed storage
- Regular integrity verification
- Automated format migration

### 9.2 Best Practices

1. **Encryption Keys**
   - Generate keys using CSPRNG (Cryptographically Secure PRNG)
   - Store keys separately from capsule data
   - Use hardware security modules (HSM) for high-value capsules

2. **Access Control**
   - Implement least-privilege principle
   - Require multi-party authorization for sensitive capsules
   - Maintain detailed audit logs

3. **Storage**
   - Use geographically distributed storage
   - Maintain at least 3 copies (3-2-1 backup rule)
   - Regular integrity verification

4. **Monitoring**
   - Automated health checks
   - Alert on integrity violations
   - Regular format obsolescence scans

## 10. Compliance and Standards

### 10.1 Compatible Standards

- **ISO 14721 (OAIS)**: Open Archival Information System
- **PDF/A**: Archival PDF format
- **PREMIS**: Preservation Metadata
- **Dublin Core**: Metadata standards

### 10.2 Regulatory Compliance

The standard supports compliance with:
- GDPR (data protection and privacy)
- HIPAA (healthcare records retention)
- SEC/FINRA (financial records retention)
- ISO 27001 (information security)

## 11. Implementation Guidelines

### 11.1 Minimum Requirements

**Client:**
- TLS 1.3 for API communication
- Support for Ed25519 signatures
- AES-256-GCM encryption capability

**Server:**
- RESTful API server
- Secure key storage (HSM or KMS)
- Multiple storage backends
- Blockchain integration (optional)

### 11.2 Performance Targets

- Capsule creation: < 5 seconds (excluding upload)
- Content upload: 10 MB/s minimum
- Sealing operation: < 30 seconds
- Integrity verification: < 10 seconds

## 12. Future Extensions

### 12.1 Planned Features

- **Quantum-resistant cryptography**: Post-quantum encryption algorithms
- **AI-powered format migration**: Machine learning for automatic conversion
- **Zero-knowledge proofs**: Privacy-preserving verification
- **Decentralized governance**: Community-driven capsule verification

### 12.2 Version Compatibility

This specification (v1.0) maintains backward compatibility guarantees:
- v1.x releases: Backward compatible
- v2.x releases: Migration path provided
- Deprecated features: 2-year sunset period

## 13. References

### 13.1 Cryptographic Standards

- NIST FIPS 197: AES Specification
- RFC 8032: EdDSA (Ed25519)
- NIST FIPS 202: SHA-3 Standard

### 13.2 Related Specifications

- WIA-INTENT: Intent-based interaction standard
- WIA-OMNI-API: Universal API specification
- ISO 14721: OAIS Reference Model

---

## Appendix A: Example Implementation

See `/api/typescript/` for complete TypeScript implementation.

## Appendix B: Test Vectors

Cryptographic test vectors available at:
`https://github.com/WIA-Official/wia-standards/test-vectors/`

## Appendix C: Migration Tools

Format migration tools and libraries:
`https://github.com/WIA-Official/wia-standards/migration-tools/`

---

**Document Status:** Production Ready
**Last Updated:** January 2025
**Next Review:** January 2026

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