# PART 2: Existing subsystems to reuse instead of building be… (1)

Checks 1 to 4 of 5, each with its evidence

## What you can do here

- **Verify 1: UK Open Banking Read/Write API v4.0.x (Open…**: Verify: UK Open Banking Read/Write API v4.0.x (OpenAPI files) | Spec | No LIC…
- **Verify 2: FAPI 2.0 Security Profile and Message Signi…**: Verify: FAPI 2.0 Security Profile and Message Signing | Spec | OIDF Final (pu…
- **Verify 3: OpenID AuthZEN Authorization API 1.0 | Spec…**: Verify: OpenID AuthZEN Authorization API 1.0 | Spec | OIDF Final (published)…
- **Verify 4: ISO 20022 | Messaging standard | published…**: Verify: ISO 20022 | Messaging standard | published (ISO). Library: Prowide Ap…
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- **Open Meet the research: 2.4 Open banking and **