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Every checkout session gets a unique deposit address. This is fundamental to the non-custodial design: the merchant controls the seed, and every address is deterministically derived from it — no third party can generate or predict the addresses.

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HD wallet (BIP-44)

My Crypto Server uses BIP-44 hierarchical deterministic (HD) wallets. One BIP-39 mnemonic phrase (12 or 24 words) generates an entire tree of addresses.

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Derivation paths

The index is the session’s derivation index — an auto-incrementing counter stored in the database. Session 1 gets index 0, session 2 gets index 1, and so on. Each session always uses the same address — the index is allocated at creation and never reused.

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Seed storage

The mnemonic is provided during initial setup via the dashboard’s setup wizard. It is:
  1. Never stored in plaintext.
  2. Encrypted with AES-256-GCM using a key derived from scrypt(MASTER_PASSPHRASE, salt=fingerprint).
  3. The encrypted blob is stored in the database.
MASTER_PASSPHRASE is the only secret you need to keep to recover your seed. Loss of the passphrase means loss of access to the encrypted seed.

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Verification

After entering your seed, the dashboard derives the first 3 addresses and shows them. Verify these match what your hardware wallet or Metamask shows for the same mnemonic — this confirms derivation is working correctly before you go live.

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Why unique addresses?

Using a unique address per session:
  • Makes payment detection unambiguous — a transfer to address X can only belong to session Y.
  • Prevents session confusion if a customer pays twice for the same link.
  • Lets the on-chain history of each address be independently auditable.
After a session is paid and swept, that address is retired. The sweep moves all funds out, leaving it empty for easy auditing.

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Adding new chains

Each chain has a ChainAdapter implementation. To support a new chain, register it in src/lib/chain/registry.ts and implement the adapter interface (deriveAddress, getHead, fetchTransfersTo, checkFinality, sweepNative). The rest of the pipeline is chain-agnostic.