# Satoshi Protocol

## Terminology & Abbreviation <a href="#nearsatoshiprotocol-terminology-and-abbreviation" id="nearsatoshiprotocol-terminology-and-abbreviation"></a>

| Abbr.           | Description                                                                                                             |
| --------------- | ----------------------------------------------------------------------------------------------------------------------- |
| Addr            | The base58 format address generated from PK                                                                             |
| BC              | The bridge smart contract in Near, assuming its contract ID is bridge.near                                              |
| Bitcoin Relayer | Help to broadcast Bitcoin withdrawal transactions to Bitcoin network.                                                   |
| CA              | CSNA Assistant, lives on the user's side, help user invoking BTC wallet to sign message.                                |
| CSNA            | Chain signature Near account, a sub-account of BC, uses dAddr as its ID. This is the user’s non-custodian near account. |
| dAddr           | The user’s exclusive deposit address in base58 format generated from dPK                                                |
| dPK             | a Bitcoin public key generated through NEAR Chain Abastaction where PK is the path and BC is the predecessor account    |
| DTL             | Deposit Bitcoin Tx Listener.                                                                                            |
| MDS             | Message delivery Service.                                                                                               |
| MetaTx Relayer  | NEAR Meta-Transaction Relayer for NSP message operations.                                                               |
| nPK             | A Near EdDSA public key generated through NEAR Chain Abstraction where PK is the path and BC is the predecessor account |
| NSP frontend    | the frontend pages of the bridge dapp lived on the user’s side, mainly used for deposit and withdrawal.                 |
| PK              | User’s bitcoin public key whose corresponding secret key will be used to sign messages                                  |
| smTX            | The signed Near Tx comes from a user’s message.                                                                         |
| ST              | Signing Trigger, help to trigger BC to request Chain Signature for withdrawal TXs.                                      |
| TC              | Mapping Token Contract, currently means nBTC token contract.                                                            |
| UM              | UTXO Management.                                                                                                        |
| WTL             | Withdrawal Bitcoin Tx Listener.                                                                                         |

Near Satoshi Protocol (NSP) is an bridge protocol based on Near Chain-Abstraction which not only provide assets bridge ability but allow source chain users to directly access NEAR dApps. NSP actually pushes BTC holders’ web3 user experience to a new level: With NSP, any BTC holder can **join the whole NEAR network ecosystem**, without introducing any new wallet, or any new key pairs. Just **using their familiar BTC wallet**, BTC holders can play with all dApps on the NEAR network, with **only BTC as on-chain gas**, and enjoy the **seconds finality speed of the NEAR network**.

Let’s see how NSP can achieve that. There are roughly 3 basic questions involved in any bridge:

* How to bridge assets out of Bitcoin? Aka, deposit.
* How to use those bridged assets?
* How to bridge assets back to Bitcoin? Aka, withdrawal.


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