Rehydrate Functions

Rehydration is the process of replacing placeholder tags with original values.

rehydrate()

Replaces PII placeholders with original values.

Signature

function rehydrate(
  text: string,
  piiMap: Map<string, string>,
  strict?: boolean,
  tagFormat?: TagFormat
): string

Parameters

string

required

Text containing PII placeholder tags

Map<string, string>

required

Decrypted PII map from decryptPIIMap()

boolean

default:"false"

If true, use strict matching (exact tag format only). If false, use fuzzy matching that handles mangled tags from translation.

TagFormat

Tag format configuration. Must match the format used during anonymization. Defaults to XML-style (<PII type="..." id="N"/>).

Returns

Text with placeholders replaced by original values.

Example

import { rehydrate, decryptPIIMap } from 'rehydra';

// After anonymization and translation
const translated = 'Hallo <PII type="PERSON" id="1"/> von <PII type="ORG" id="1"/>!';

// Decrypt the PII map
const key = await keyProvider.getKey();
const piiMap = await decryptPIIMap(result.piiMap, key);
// Map { 'PERSON:1' => 'John Smith', 'ORG:1' => 'Acme Corp' }

// Rehydrate
const original = rehydrate(translated, piiMap);
// "Hallo John Smith von Acme Corp!"

decryptPIIMap()

Decrypts the encrypted PII map from an anonymization result.

Signature

function decryptPIIMap(
  encryptedMap: EncryptedPIIMap,
  key: Uint8Array
): Promise<Map<string, string>>

Parameters

EncryptedPIIMap

required

The encrypted PII map from result.piiMap

interface EncryptedPIIMap {
  ciphertext: string;  // Base64
  iv: string;          // Base64
  authTag: string;     // Base64
}

Uint8Array

required

The encryption key (same key used during anonymization)

Returns

A Map<string, string> where:

Key: "TYPE:id" (e.g., "EMAIL:1", "PERSON:2")
Value: Original PII value

Example

import { decryptPIIMap, InMemoryKeyProvider } from 'rehydra';

const keyProvider = new InMemoryKeyProvider();

// During anonymization
const anonymizer = createAnonymizer({ keyProvider });
const result = await anonymizer.anonymize('Email: john@example.com');

// Later, to rehydrate
const key = await keyProvider.getKey();
const piiMap = await decryptPIIMap(result.piiMap, key);

console.log(piiMap.get('EMAIL:1'));  // "john@example.com"

Complete Workflow

import { 
  createAnonymizer,
  decryptPIIMap,
  rehydrate,
  InMemoryKeyProvider
} from 'rehydra';

// 1. Setup
const keyProvider = new InMemoryKeyProvider();
const anonymizer = createAnonymizer({
  ner: { mode: 'quantized' },
  keyProvider
});
await anonymizer.initialize();

// 2. Anonymize
const result = await anonymizer.anonymize(
  'Contact John Smith at john@acme.com'
);
console.log(result.anonymizedText);
// "Contact <PII type="PERSON" id="1"/> at <PII type="EMAIL" id="1"/>"

// 3. Process (e.g., translate)
const translated = await translate(result.anonymizedText);
// "Kontaktieren Sie <PII type="PERSON" id="1"/> unter <PII type="EMAIL" id="1"/>"

// 4. Decrypt PII map
const key = await keyProvider.getKey();
const piiMap = await decryptPIIMap(result.piiMap, key);

// 5. Rehydrate
const final = rehydrate(translated, piiMap);
console.log(final);
// "Kontaktieren Sie John Smith unter john@acme.com"

// 6. Cleanup
await anonymizer.dispose();

Session-Based Rehydration

When using sessions, rehydration is simplified:

const session = anonymizer.session('chat-123');

// Anonymize (auto-saves PII map)
const result = await session.anonymize('Hello John Smith!');

// Rehydrate (auto-loads and decrypts)
const original = await session.rehydrate(result.anonymizedText);

See Sessions for details.

Placeholder Format

By default, rehydrate expects placeholders in XML-style format:

<PII type="TYPE" id="N"/>
<PII type="TYPE" id="N" gender="..."/>
<PII type="TYPE" id="N" scope="..."/>

When using a custom tag format, pass the same tagFormat used during anonymization:

const tagFormat = { open: '[[', close: ']]' };
const text = '[[PII type="PERSON" id="1"]] from [[PII type="ORG" id="2"]]';
const result = rehydrate(text, piiMap, false, tagFormat);

The function matches based on type and id attributes.

Handling Malformed Placeholders

const text = 'Hello <PII type="PERSON" id="1"/> and <BROKEN/>';
const result = rehydrate(text, piiMap);
// "Hello John Smith and <BROKEN/>"
// Unmatched tags are preserved

Error Handling

Missing Key

try {
  const piiMap = await decryptPIIMap(result.piiMap, wrongKey);
} catch (error) {
  // "Decryption failed: invalid key or corrupted data"
}

Missing PII Entry

const piiMap = new Map([['EMAIL:1', 'test@example.com']]);
const text = '<PII type="PERSON" id="1"/>';  // Not in map

const result = rehydrate(text, piiMap);
// "<PII type="PERSON" id="1"/>"  // Unchanged (no match)

Encryption - How PII maps are encrypted
Sessions - Simplified rehydration with sessions
Crypto - Key management utilities

Overview

Core

Storage

Streaming & Proxy

Utilities

rehydrate()

Signature

Parameters

Returns

Example

decryptPIIMap()

Signature

Parameters

Returns

Example

Complete Workflow

Session-Based Rehydration

Placeholder Format

Handling Malformed Placeholders

Error Handling

Missing Key

Missing PII Entry

​rehydrate()

​Signature

​Parameters

​Returns

​Example

​decryptPIIMap()

​Signature

​Parameters

​Returns

​Example

​Complete Workflow

​Session-Based Rehydration

​Placeholder Format

​Handling Malformed Placeholders

​Error Handling

​Missing Key

​Missing PII Entry

​Related

rehydrate()

Signature

Parameters

Returns

Example

decryptPIIMap()

Signature

Parameters

Returns

Example

Complete Workflow

Session-Based Rehydration

Placeholder Format

Handling Malformed Placeholders

Error Handling

Missing Key

Missing PII Entry

Related