Addresses

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Source code: address.js

Note that addresses are handled automatically by Money Button behind the scenes and it is not necessary to deal with addresses directly unless you are building an advanced application.

A Bitcoin address is the hash of a public key. It is hashed twice (SHA256 and then RIPEMD160). Although we do not know for sure why Satoshi designed addresses this way, it is likely the two layers of hashing are there to provide an extra layer of security in case the underlying elliptic curve cryptography is ever broken. If attackers have to break through two hash functions just to get your public key, that makes attacks on the public key harder.

Addresses are 20 bytes long in raw buffer format but are almost always encoded in Base 58 Check format, which is a convenient format for using on the internet. It is also robust against copy errors - if an error occurs in copying, the address is no longer valid, meaning you are very unlikely to send money to an address for which no one has the private key.

Addresses are derived from public keys, which in turn are derived from private keys. Two convenience methods allow you to derive addresses either from the public key or directly from the private key. For instance:

let privateKey = bsv.PrivKey.fromRandom()
let publicKey = bsv.PubKey.fromPrivKey(privateKey)
let address = bsv.Address.fromPubKey(publicKey)
let address2 = bsv.Address.fromPrivKey(privateKey)

console.log(address.toString())
// prints:
// 1JvFXyZMC31ShnD8PSKgN1HKQ2kGQLVpCt

console.log(address2.toString())
// prints:
// 1JvFXyZMC31ShnD8PSKgN1HKQ2kGQLVpCt

You can use mainnet or testnet. Everything is mainnet by default, but if you are developing an app and want to do lots of testing without risking losing real money, you may want to use testnet. For instance:

let privateKey = bsv.PrivKey.fromRandom('testnet')
let publicKey = bsv.PubKey.fromPrivKey(privateKey)
let address = bsv.Address.fromPubKey(publicKey, 'testnet')
let address2 = bsv.Address.fromPrivKey(privateKey, 'testnet')

console.log(address.toString())
// prints:
// n2DoUfi8oUkTALKdd3AvVeTTyWg1AQmXCD

console.log(address2.toString())
// prints:
// n2DoUfi8oUkTALKdd3AvVeTTyWg1AQmXCD

Mainnet addresses always start with a '1' and testnet addresses always start either with an 'm' or an 'n'.

You can also read an address back in and print it back out again:

let address = bsv.Address.fromString('1JvFXyZMC31ShnD8PSKgN1HKQ2kGQLVpCt')

console.log(address.toString())
// prints:
// 1JvFXyZMC31ShnD8PSKgN1HKQ2kGQLVpCt

Invalid addresses will throw an error if you try to read them in.

P2SH is a deprecated way to create addresses on Bitcoin SV. The way P2SH works is that the output script is the hash of another script called the redeem script. The redeem script is a third script contained inside a pushdata in the spending input script. It is not recommended to use P2SH for anything, however bsv will maintain support so long as this style of script is being created on the blockchain.

The key difference for a P2SH address is that it is the hash of a script instead of a public key and that in Base 58 format it starts with a '3' instead of a '1'.

An example is:

let script = bsv.Script.fromString('OP_RETURN')
let address = bsv.Address.payingTo(script)

console.log(address.toString())
// prints:
// 37gsHDLSG5TJvApGfiUZDaDo9mSr6rjLv6

This example shows you what a P2SH address looks like, but this script would not actually work on the blockchain because the OP_RETURN would invalidate the transaction.