PII Redaction

Chorum can automatically detect and redact personally identifiable information (PII) before sending data to LLM providers.

Why This Matters

When you paste code, logs, or data into a chat, you might accidentally include sensitive information—an email address, a phone number, a credit card from test data. PII redaction catches these before they leave your machine.

What’s Detected

Chorum detects and redacts four types of PII:

Credit Card Numbers

Detection: 13-19 digit sequences with optional separators (spaces, dashes). Validated using the Luhn algorithm.

Note: Only valid credit card numbers are redacted. Random 16-digit sequences that fail Luhn validation are left alone.

Social Security Numbers (SSN)

Detection: 9-digit numbers in SSN format. Excludes invalid patterns (000, 666, 900-999 in first group).

Email Addresses

Detection: Standard email pattern recognition.

Note: The domain is preserved for context. The local part is masked.

Phone Numbers

Detection: US phone number formats (10-11 digits).

How It Works

When Redaction Happens

PII redaction runs before data leaves your browser:

Your Message
     ↓
┌──────────────┐
│ PII Scanner  │  ← Runs client-side
└──────────────┘
     ↓
Redacted Message → LLM Provider

The LLM never sees the original PII. Your actual email address, phone number, or credit card stays on your machine.

What the LLM Sees

Instead of:

Contact customer john.doe@acme.com at 555-123-4567
regarding charge to card 4111-1111-1111-1111

The LLM receives:

Contact customer [EMAIL j***e@acme.com] at [PHONE ***-***-4567]
regarding charge to card [CARD ****1111]

Enabling/Disabling

Via Settings

1. Go to Settings → Security
2. Find Anonymize PII
3. Toggle on or off

When to Enable

When to Disable

• Working with intentionally fake data where detection is a false positive
• Need to discuss actual email domains or phone patterns with the AI
• Debugging the redaction system itself

Example: Redaction in Action

Before (your input):

Debug this customer record:
{
  "name": "John Smith",
  "email": "john.smith@bigcompany.com",
  "phone": "(555) 867-5309",
  "ssn": "123-45-6789",
  "card": "4532 7890 1234 5678"
}

After (sent to LLM):

Debug this customer record:
{
  "name": "John Smith",
  "email": "[EMAIL j***h@bigcompany.com]",
  "phone": "[PHONE ***-***-5309]",
  "ssn": "[SSN ***-**-6789]",
  "card": "[CARD ****5678]"
}

Confidence Levels

Each detection has a confidence level:

Phone numbers are “medium” confidence because 10-digit sequences appear in other contexts (order numbers, IDs, etc.).

Limitations

What’s NOT Detected

False Positives

Some valid data may be incorrectly flagged:

• 10-digit order numbers flagged as phones
• Test data with valid-format SSNs
• Example code with realistic-looking credit cards

If false positives are an issue, you can:

1. Disable PII redaction for that session
2. Accept that some legitimate numbers will be masked

False Negatives

Some PII might slip through:

• International phone formats (non-US)
• Unusual email formats
• Credit cards from non-standard issuers

The system errs on the side of not false-positive flagging.

Technical Implementation

The redaction happens in src/lib/pii.ts:

// Core scanning function
export function anonymizePii(text: string): AnonymizeResult {
  const matches: PiiMatch[] = [];
  let result = text;
  
  // Credit card detection with Luhn validation
  result = result.replace(creditCardRegex, (match) => {
    if (isValidLuhn(match.replace(/\D/g, ''))) {
      const lastFour = match.slice(-4);
      return `[CARD ****${lastFour}]`;
    }
    return match;
  });
  
  // ... SSN, email, phone patterns
  
  return { text: result, matches, wasModified: matches.length > 0 };
}

FAQ

Does redaction affect memory storage?

No. Memory storage sees the original text. Redaction only applies when sending to external LLM providers.

Can I see what was redacted?

Yes. When redaction occurs, the audit log (if enabled) records:

• That redaction happened
• Types of PII found (not the actual values)

Does this work with local models?

PII redaction can be disabled for local models if you prefer. Since data never leaves your machine with local models, the privacy concern is different.

Can I customize patterns?

Not currently. Future versions may allow custom PII patterns.

Related Documentation

• Sovereignty Overview — Why privacy matters
• Security Settings — All security options
• Local-First — Running without cloud exposure