Tiago
72 lines
2.4 KiB
Markdown
72 lines
2.4 KiB
Markdown
# How does cap work?
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> [!NOTE]
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> This is a more technical explanation of how Cap works. If you're looking for a more general overview, check out the [Effectiveness](./effectiveness.md) page.
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```mermaid
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sequenceDiagram
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participant User
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participant W as Widget
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participant WW as WASM Solver
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participant S as Server
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User->>W: Interaction
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W->>S: Request challenge
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activate S
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S->>S: Generate challenge
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S-->>W: Return challenge
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deactivate S
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W->>WW: Distribute work
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Note over WW: for each challenge
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activate WW
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WW->>WW: Solve SHA-256 PoW
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WW-->>W: Return solutions
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deactivate WW
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W->>S: Submit solutions
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activate S
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S->>S: Verify solutions
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S-->>W: Return token
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deactivate S
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W-->>User: Send token
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Note over User,S: Later requests
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# Assuming user interaction triggers the widget for later requests
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# User->>W: (Initiate later request)
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W->>S: Send token with request
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activate S
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S->>S: Validate token
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Note over S: Success!
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deactivate S
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```
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#### Initialization
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1. When Cap is initialized, it automatically registers a custom element for the widget in the browser's DOM.
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2. The widget creates a shadow DOM and appends all necessary HTML elements to it, ensuring encapsulation from the rest of the page.
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#### Requesting the challenge
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3. When a solution is requested, the widget sends a request to the server to create a challenge set.
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- Each challenge consists of a unique salt and a target hash prefix.
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- The goal is to find a nonce value that, when combined with the salt and hashed using SHA-256, produces a hash that begins with the target prefix.
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- Instead of generating just one challenge, Cap creates multiple challenges to enable progress tracking and optimize performance.
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#### Computing the solution
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4. The widget leverages Web Workers to solve the challenges in parallel:
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- Each worker attempts to find a valid nonce by repeatedly:
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- Combining the salt with different nonce values
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- Computing the SHA-256 hash of this combination
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- Checking if the resulting hash begins with the target prefix
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- Workers increment the nonce systematically until a matching hash is found
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#### Redeeming the solution for a token
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5. Once a valid solution is found, the widget sends the result back to the server for validation.
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6. Upon successful verification, the server redeems the solution and issues a token that can be used to authenticate the request.
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