📦 Download and Decrypt Results

When an iApp execution completes, you need to retrieve and decrypt the results. This guide shows you how to download task results and decrypt them to access the actual output files.

Understanding the result retrieval process is essential for building user-friendly applications with iExec.

Understanding Results Structure

Deal → Task → Result Flow

Every execution follows this hierarchy:

Deal (agreement between parties)
├── Task 1 (individual execution instance)
│   └── Result (encrypted output files)
├── Task 2
│   └── Result
└── ...

• Deal: Contains one or more tasks from your execution request
• Task: Individual computation instance with unique taskId
• Result: Encrypted ZIP file containing your iApp's output files

Result Accessibility

Results are publicly downloadable but may be encrypted:

• ✅ Anyone can download the result file from IPFS
• 🔒 Only authorized parties can decrypt the contents
• 📁 Results contain all files from IEXEC_OUT directory
• ⚡ Available immediately after task completion

Download & Decrypt Results

DataProtector provides methods to download and decrypt results from completed tasks. You can view the taskId in your iExec Explorer.

// Get result from a completed task
const result = await dataProtectorCore.getResultFromCompletedTask({
  taskId: '0x123abc...', // Your task ID
});

console.log('Result downloaded and decrypted:', result);

Info

The processProtectedData method will create a task and automatically download and decrypt the result.

Result File Structure

What's Inside a Result

Typical result contents:

result.zip
├── computed.json         # Mandatory metadata file
├── result.txt           # Your main output
├── analysis.json        # Additional outputs
├── logs.txt            # Optional logs
└── metadata.json       # Optional metadata

computed.json Structure

Always present in every result:

{
  "deterministic-output-path": "/iexec_out/result.txt",
  "execution-timestamp": "2024-01-15T10:30:00Z",
  "app-version": "1.0.0"
}

Key fields:

• deterministic-output-path: Main result file path
• execution-timestamp: When the computation completed
• Custom fields added by your iApp

Common Patterns

React Application Example

Integrate result retrieval in your frontend:

async function downloadResult(taskId: string) {
  try {
    const resultResponse = await dataProtectorCore.getResultFromCompletedTask({
      taskId,
    });

    // Convert to text or JSON based on your result format
    const resultText = new TextDecoder().decode(resultResponse.result);
    const resultJson = JSON.parse(resultText);

    return resultJson;
  } catch (error) {
    console.error('Failed to download result:', error);
    throw error;
  }
}

// Usage example
const taskId = '0x123abc...';
const result = await downloadResult(taskId);
console.log('Analysis Result:', result);

Node.js Backend Example

Server-side result processing:

const {
  IExecDataProtectorCore,
  getWeb3Provider,
} = require('@iexec/dataprotector');

async function processTaskResult(taskId) {
  const web3Provider = getWeb3Provider(process.env.PRIVATE_KEY);
  const dataProtectorCore = new IExecDataProtectorCore(web3Provider);

  try {
    // Get the result
    const resultBuffer = await dataProtectorCore.getResultFromCompletedTask({
      taskId,
    });

    // Parse the result based on your format
    const resultText = new TextDecoder().decode(resultBuffer);

    // If your result is JSON
    const analysisResult = JSON.parse(resultText);

    // Store in database, send notifications, etc.
    await saveToDatabase(taskId, analysisResult);
    await notifyUser(analysisResult);

    return analysisResult;
  } catch (error) {
    console.error('Result processing failed:', error);
    throw error;
  }
}

Troubleshooting

Common Issues

❌ "Task not completed"

Error: Task is still running

Solution: Wait for task completion or check status with iexec task show <taskId>

❌ "Decryption failed"

Error: Failed to decrypt result

Solutions:

• Use the correct wallet (beneficiary)
• Check if result was actually encrypted
• Verify task completed successfully

❌ "Result not found"

Error: Result not available

Solutions:

• Check task status - it might have failed
• Verify the task ID is correct
• Wait for result upload to complete

Checking Task Status

Before downloading, verify completion:

# Check if task is completed
iexec task show <taskId>

# Look for status: "COMPLETED"
# And result information in the output

Result Encryption Status

Not all results are encrypted:

• 🔒 Encrypted: When beneficiary is set in the request
• 📂 Plain: When no beneficiary specified (public results)
• ✅ DataProtector handles both automatically

What's Next?

You can now retrieve and decrypt iApp results!

Integrate result handling into your applications:

• Inputs and Outputs - Understand what your iApp can output
• Debugging Your iApp - Troubleshoot execution issues
• App Access Control and Pricing - Control who can run your iApp

Advanced Topics

• DataProtector SDK - Complete SDK documentation
• SDK Deep Dive - Advanced result handling techniques