Anonymization & Pseudonymization

Rehydra supports two closely related ways to protect sensitive text: pseudonymize for reversible workflows and anonymize for irreversible ones.

The Two Modes

Mode	What happens	Can you restore originals later?	Typical use
`pseudonymize`	Rehydra replaces detected values with placeholders and returns an encrypted `piiMap`	Yes	Apps, agents, and workflows that need later rehydration
`anonymize`	Rehydra replaces detected values with placeholders and discards the original-value mapping	No	One-way redaction and irreversible sharing

import { createAnonymizer } from 'rehydra';

const reversible = createAnonymizer({ mode: 'pseudonymize' });
const irreversible = createAnonymizer({ mode: 'anonymize' });

Shared Processing Model

Both modes use the same high-level flow:

Detect

Rehydra runs enabled recognizers and optional NER to identify sensitive spans.

Resolve

Overlaps are resolved using type priority and confidence rules.

Replace

Original values are swapped for stable <PII .../> placeholders.

Store or discard

In pseudonymize mode Rehydra encrypts the mapping; in anonymize mode it does not keep one.

Placeholder Output

Rehydra uses XML-like placeholders so downstream systems can safely process the text while preserving structure.

<PII type="EMAIL" id="1"/>
<PII type="PERSON" id="1"/>

When semantic enrichment is enabled, placeholders can include extra attributes:

<PII type="PERSON" gender="female" id="1"/>
<PII type="LOCATION" scope="city" id="2"/>

Choosing the Right Mode

Use pseudonymize when:

You need to restore the original values later
You are building an application flow around rehydration
You want encrypted mappings for sessions or agent workflows

Use anonymize when:

You want irreversible protection
You are preparing text for one-way sharing or analysis
You do not want to manage keys or stored mappings

pseudonymize naturally connects to rehydration, encryption, and key management. anonymize is simpler, but it still depends on the same recognizers, type system, and configuration model.

Getting Started

Core Concepts

Guides

Anonymization & Pseudonymization

The Two Modes

Shared Processing Model

Placeholder Output

Choosing the Right Mode

Next Steps

Rehydration

Configuration

​The Two Modes

​Shared Processing Model

​Placeholder Output

​Choosing the Right Mode

​Related Concepts

​Next Steps

Rehydration

Configuration

The Two Modes

Shared Processing Model

Placeholder Output

Choosing the Right Mode

Related Concepts

Next Steps