Mastering Bitcoin: Programming the Open Blockchain (2017)

Appendix G. Bitcoin Explorer (bx) Commands

Bitcoin Explorer (bx) is a command-line tool that offers a variety of commands for key management and transaction construction. It is part of the libbitcoin bitcoin library.

Usage: bx COMMAND [--help]

Info: The bx commands are:

address-decode

address-embed

address-encode

address-validate

base16-decode

base16-encode

base58-decode

base58-encode

base58check-decode

base58check-encode

base64-decode

base64-encode

bitcoin160

bitcoin256

btc-to-satoshi

ec-add

ec-add-secrets

ec-multiply

ec-multiply-secrets

ec-new

ec-to-address

ec-to-public

ec-to-wif

fetch-balance

fetch-header

fetch-height

fetch-history

fetch-stealth

fetch-tx

fetch-tx-index

hd-new

hd-private

hd-public

hd-to-address

hd-to-ec

hd-to-public

hd-to-wif

help

input-set

input-sign

input-validate

message-sign

message-validate

mnemonic-decode

mnemonic-encode

ripemd160

satoshi-to-btc

script-decode

script-encode

script-to-address

seed

send-tx

send-tx-node

send-tx-p2p

settings

sha160

sha256

sha512

stealth-decode

stealth-encode

stealth-public

stealth-secret

stealth-shared

tx-decode

tx-encode

uri-decode

uri-encode

validate-tx

watch-address

wif-to-ec

wif-to-public

wrap-decode

wrap-encode

For more information, see the Bitcoin Explorer homepage and Bitcoin Explorer user documentation.

Examples of bx Command Use

Let’s look at some examples of using Bitcoin Explorer commands to experiment with keys and addresses.

Generate a random “seed” value using the seed command, which uses the operating system’s random number generator. Pass the seed to the ec-new command to generate a new private key. We save the standard output into the file private_key:

$ bx seed | bx ec-new > private_key

$ cat private_key

73096ed11ab9f1db6135857958ece7d73ea7c30862145bcc4bbc7649075de474

Now, generate the public key from that private key using the ec-to-public command. We pass the private_key file into the standard input and save the standard output of the command into a new file public_key:

$ bx ec-to-public < private_key > public_key

$ cat public_key

02fca46a6006a62dfdd2dbb2149359d0d97a04f430f12a7626dd409256c12be500

We can reformat the public_key as an address using the ec-to-address command. We pass the public_key into standard input:

$ bx ec-to-address < public_key

17re1S4Q8ZHyCP8Kw7xQad1Lr6XUzWUnkG

Keys generated in this manner produce a type-0 nondeterministic wallet. That means that each key is generated from an independent seed. Bitcoin Explorer commands can also generate keys deterministically, in accordance with BIP-32. In this case, a “master” key is created from a seed and then extended deterministically to produce a tree of subkeys, resulting in a type-2 deterministic wallet.

First, we use the seed and hd-new commands to generate a master key that will be used as the basis to derive a hierarchy of keys:

$ bx seed > seed

$ cat seed

eb68ee9f3df6bd4441a9feadec179ff1

$ bx hd-new < seed > master

$ cat master

xprv9s21ZrQH143K2BEhMYpNQoUvAgiEjArAVaZaCTgsaGe6LsAnwubeiTcDzd23mAoyizm9cApe51gNfLMkBqkYoWWMCRwzfuJk8RwF1SVEpAQ

We now use the hd-private command to generate a hardened “account” key and a sequence of two private keys within the account:

$ bx hd-private --hard < master > account

$ cat account

xprv9vkDLt81dTKjwHB8fsVB5QK8cGnzveChzSrtCfvu3aMWvQaThp59ueufuyQ8Qi3qpjk4aKsbmbfxwcgS8PYbgoR2NWHeLyvg4DhoEE68A1n

$ bx hd-private --index 0 < account

xprv9xHfb6w1vX9xgZyPNXVgAhPxSsEkeRcPHEUV5iJcVEsuUEACvR3NRY3fpGhcnBiDbvG4LgndirDsia1e9F3DWPkX7Tp1V1u97HKG1FJwUpU

$ bx hd-private --index 1 < account

xprv9xHfb6w1vX9xjc8XbN4GN86jzNAZ6xHEqYxzbLB4fzHFd6VqCLPGRZFsdjsuMVERadbgDbziCRJru9n6tzEWrASVpEdrZrFidt1RDfn4yA3

Next, we use the hd-public command to generate the corresponding sequence of two public keys:

$ bx hd-public --index 0 < account

xpub6BH1zcTuktiFu43rUZ2gXqLgzu5F3tLEeTQ5t6iE3aQtM2VMTxMcyLN9fYHiGhGpQe9QQYmqL2eYPFJ3vezHz5wzaSW4FiGrseNDR4LKqTy

$ bx hd-public --index 1 < account

xpub6BH1zcTuktiFx6CzhPbGjG3UYQ13WR16CmtbPiagEKpEVtpyjshWyMaMV1cn7nUPUkgQHPVXJVqsrA8xWbGQDhohEcDFTEYMvYzwRD7Juf8

The public keys can also be derived from their corresponding private keys using the hd-to-public command:

$ bx hd-private --index 0 < account | bx hd-to-public

xpub6BH1zcTuktiFu43rUZ2gXqLgzu5F3tLEeTQ5t6iE3aQtM2VMTxMcyLN9fYHiGhGpQe9QQYmqL2eYPFJ3vezHz5wzaSW4FiGrseNDR4LKqTy

$ bx hd-private --index 1 < account | bx hd-to-public

xpub6BH1zcTuktiFx6CzhPbGjG3UYQ13WR16CmtbPiagEKpEVtpyjshWyMaMV1cn7nUPUkgQHPVXJVqsrA8xWbGQDhohEcDFTEYMvYzwRD7Juf8

We can generate a practically limitless number of keys in a deterministic chain, all derived from a single seed. This technique is used in many wallet applications to generate keys that can be backed up and restored with a single seed value. This is easier than having to back up the wallet with all its randomly generated keys every time a new key is created.

The seed can be encoded using the mnemonic-encode command:

$ bx hd-mnemonic < seed > words

adore repeat vision worst especially veil inch woman cast recall dwell appreciate

The seed can then be decoded using the mnemonic-decode command:

$ bx mnemonic-decode < words

eb68ee9f3df6bd4441a9feadec179ff1

Mnemonic encoding can make the seed easier to record and even remember.