Mastering Bitcoin

Appendix D. Bitcoin Explorer (bx) Commands

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 home page 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 BIP0032. 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 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.