Core Concepts

Core Concepts

This section covers the fundamental concepts you need to understand when building on Doxa.

Internet Computer Basics

Authentication Flow

Developer -> DApp: Initiate auth
DApp -> NFID: Redirect auth request
NFID -> User: Biometric auth
User -> NFID: Approve
NFID -> DApp: Return principal ID
DApp -> Canister: Call with auth header

Canisters

Canisters are the smart contracts of the Internet Computer. They are:

• Autonomous
• Deterministic
• Upgradeable
• Interoperable

Example of a basic canister:

actor {
    private var state = 0;
    
    public func increment() : async Nat {
        state += 1;
        state
    };
    
    public query func get() : async Nat {
        state
    };
}

Cycles

Cycles are the fuel that powers your canisters on the IC. They:

• Are pegged to XDR (Special Drawing Rights)
• Can be transferred between canisters
• Need to be managed carefully

Check cycle balance:

public query func get_cycle_balance() : async Nat {
    Cycles.balance()
};

Principal IDs

Principal IDs are unique identifiers for:

• Canisters
• Users
• Subnets

They look like this: xeka7-7iaaa-aaaab-qabra-cai

Candid

Candid is the interface description language for the Internet Computer. It:

• Defines canister interfaces
• Handles data serialization
• Provides type safety

Example Candid interface:

type Result = variant {
    Ok: nat64;
    Err: text;
};

service : {
    create_pool: (Principal, Principal) -> (Result);
}