Addresses, keys & wallets

Every Dogecoin app eventually comes down to keys: who holds them, where addresses come from, and what you must never do with them. This lesson builds the vocabulary you'll use in every later lesson – and in every code review of a wallet-touching pull request.

From private key to D-address

The chain of custody works exactly like Bitcoin's, with Dogecoin's own cosmetic prefixes:

1. A private key is 32 random bytes. Whoever knows it can spend the funds. Full stop.
2. The matching public key is derived from it with elliptic-curve math (secp256k1, same curve as Bitcoin).
3. The public key is hashed (SHA-256, then RIPEMD-160), a version byte is prepended, a checksum is appended, and the result is Base58-encoded into an address.

That version byte is why address types are visually recognizable:

Private keys travel in WIF (Wallet Import Format) – the same Base58Check idea applied to the key itself. Treat any string like that as radioactive: never log it, never commit it, never paste it into a chat.

HD wallets: one seed, endless addresses

Modern wallets are hierarchical deterministic (HD): a single seed (those 12 or 24 words, BIP-39) deterministically generates a tree of key pairs (BIP-32). A standard derivation path (BIP-44) tells wallets where to look. Dogecoin's registered coin type is 3, so the first receiving address of the first account lives at:

m / 44' / 3' / 0' / 0 / 0

Why you care as a developer: back up the seed once and every future address is recoverable; and any wallet that follows the standard can restore any other wallet's funds. If you build wallet-adjacent software, follow the standard – users' recovery expectations depend on it.

Address hygiene for apps

• Generate a fresh address per purpose. Address reuse is bad for privacy and makes payment detection ambiguous (which payment was for which invoice?). Fresh-address-per-invoice is the backbone of the payment-detection lesson.
• Validate before you send. Dogecoin Core's validateaddress RPC tells you whether a string is a well-formed address for the network you're on – call it before every user-supplied withdrawal.
• Testnet and mainnet addresses are incompatible on purpose, so a testing mistake can't spend real funds. Develop on testnet; the prefixes will keep you honest.

The custody decision

Before writing a line of code, decide which side of this line your app lives on:

• Self-custodial: users hold their own keys (MyDoge-style). Your app never touches funds – simplest legally and safest technically, but you can't move money on users' behalf.
• Custodial: your service holds keys and owes users balances (exchange-style, and most tip bots). You gain UX power and take on real responsibility: security, accounting, and possibly regulation depending on jurisdiction and scale.

This curriculum teaches both patterns and is blunt about the responsibilities of the second. The tip-bot lesson is a guided tour of exactly this trade-off.