bitcoinbook/appdx-bx.asciidoc

[[appdx_bx]]
[appendix]

== Bitcoin Explorer (bx) Commands

((("Bitcoin Explorer (bx) commands", id="BX19_1", range="startofrange")))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 https://github.com/libbitcoin/libbitcoin-explorer[Bitcoin Explorer homepage] and https://github.com/libbitcoin/libbitcoin-explorer/wiki[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:

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$ 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:

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$ 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
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Mnemonic encoding can make the seed easier to record and even remember.(((range="endofrange", startref="BX19_1")))