> ## Documentation Index
> Fetch the complete documentation index at: https://vouch-sdk.vercel.app/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Understanding the Vouch Platform: Core Concepts

> Learn how Vouch's three modules — Identity Verification, Fraud Detection, and Escrow — work together to build end-to-end trust in your product.

Vouch is a trust infrastructure SDK that gives you three composable modules: identity verification, fraud detection, and milestone-based escrow. Each module solves a distinct problem, but they are designed to work together along a single trust lifecycle — from confirming who your users are, to assessing the risk of their actions, to holding and releasing funds only when both parties agree work is done.

## The trust lifecycle

Every secure transaction on Vouch follows the same sequence of steps. Complete each stage before moving to the next to unlock the strongest fraud signals and the lowest dispute rate.

<Steps>
  <Step title="Verify identity">
    Run `vouch.identity.verify()` to confirm a user's real-world identity against a government-issued document and a live selfie. A verified identity raises the quality of every downstream fraud signal.
  </Step>

  <Step title="Assess fraud risk">
    Call `vouch.fraud.assess()` before any sensitive action — login, payment initiation, or agreement creation. Vouch scores the action from 0–100 and returns a GREEN, AMBER, or RED flag.
  </Step>

  <Step title="Create an escrow agreement">
    Use `vouch.escrow.create()` to define milestones and the amount held in trust between a buyer and a seller. Funds are not released until both parties confirm each milestone.
  </Step>

  <Step title="Fund the agreement">
    Run `vouch.escrow.assess()` to perform a fraud check scoped to the funding event. On a GREEN result, Vouch provisions a unique virtual bank account the buyer deposits into.
  </Step>

  <Step title="Confirm milestones">
    Both the buyer and the seller must call `vouch.escrow.confirm()` for each milestone. Only when both confirmations are recorded does Vouch disburse the corresponding funds to the seller.
  </Step>
</Steps>

## The three modules

<CardGroup cols={3}>
  <Card title="Identity Verification" icon="id-card" href="/docs/concepts/identity-verification">
    Verify a user's identity with OCR document parsing, ArcFace biometric face matching, and multi-frame liveness detection. A match score of 90 or above marks the user as verified.
  </Card>

  <Card title="Fraud Detection" icon="shield-halved" href="/docs/concepts/fraud-detection">
    Score every transaction in real time using a multi-signal fraud engine that evaluates device, network, behavioral, and identity signals. Device fingerprinting is collected automatically — no setup required.
  </Card>

  <Card title="Escrow" icon="vault" href="/docs/concepts/escrow">
    Hold funds in trust across milestone-based agreements. A virtual bank account is provisioned per agreement, and funds are disbursed automatically once both parties confirm.
  </Card>
</CardGroup>

## Key terminology

Understanding the following terms will help you navigate the Vouch SDK and its API responses.

<Accordion title="PlatformUser">
  A PlatformUser is any account registered under your API key. Each PlatformUser maps to one set of identity verification results and a cumulative fraud history that Vouch uses to improve signal accuracy over time.
</Accordion>

<Accordion title="ExternalUserId">
  The `externalUserId` is the unique identifier you assign to a user in your own system — for example, a database UUID or a hashed email. You pass it to Vouch on every call so Vouch can correlate activity across sessions without storing your internal identifiers in an opaque way.
</Accordion>

<Accordion title="Agreement">
  An Agreement is an escrow contract created between a buyer and a seller. It defines the total amount, the currency, and a set of one or more Milestones. Agreements move through a defined status state machine from `PENDING` through to `DISBURSED` or `REFUNDED`.
</Accordion>

<Accordion title="Milestone">
  A Milestone is a discrete deliverable within an Agreement. Each Milestone has its own amount and description. Funds tied to a Milestone are disbursed only after both the buyer and the seller have confirmed it. Milestones move from `PENDING` → `BUYER_CONFIRMED` / `SELLER_CONFIRMED` → `COMPLETED` → `DISBURSED`.
</Accordion>

<Accordion title="FraudFlag">
  A FraudFlag is the categorical risk verdict returned by `vouch.fraud.assess()`. There are three values: `GREEN` (score 0–39, low risk), `AMBER` (score 40–69, elevated risk), and `RED` (score 70–100, high risk). Your application should branch on this value to decide whether to proceed, request step-up verification, or block the action.
</Accordion>

<Accordion title="IdentityMatchScore">
  The `identityMatchScore` is a 0–99 integer that represents the ArcFace biometric similarity between the selfie captured during verification and the portrait extracted from the submitted document. A score of 90 or above sets `identityVerified: true` on the user's profile.
</Accordion>