Bitcoin is a decentralized digital currency that operates on a peer-to-peer network with no central authority. Private keys are used to control access to bitcoins, and different wallets have different formats for storing them. Bitcoin Core and Electrum are two popular wallets that use different private key formats. In this guide, we will explore how to convert Bitcoin Core’s xprv format to Electrum’s zprv format.
Understanding Bitcoin Core’s xprv format
Bitcoin Core uses a hierarchical deterministic (HD) wallet structure, which means that a single seed can generate a tree of private and public keys. The extended private key (xprv) is the root of this tree and can be used to derive all other private keys in the wallet. The xprv format consists of a version number, a 32-byte depth, a 32-byte fingerprint, a 32-byte child number, and a 256-bit chain code. It is encrypted using the base58check cipher, which is a modified version of base58 that includes a checksum.
To convert Bitcoin Core’s xprv format to Electrum’s zprv format, we need to extract the chain code and private key from the xprv. We can do this using a variety of tools, including the bx command line tool or the pycoin Python library.
Step 1: Extract chain code and private key
To extract the chain code and private key from a Bitcoin Core xprv, we can use the bx command line tool as follows:
bx hd-to-ec xprv
xprv
| bx sha256 cut -c 1-8
This command converts xprv to an elliptic curve private key, computes its SHA256 hash, and then extracts the first 4 bytes (8 hexadecimal characters) of the hash as chain code. It also outputs the private key, which we will need later.
Step 2: Convert the chain code into Electrum format
Electrum uses a different format for the chain code than Bitcoin Core. In Electrum, the chain code is 32 bytes long and represented as a hexadecimal string. To convert the chain code we extracted in step 1 to the Electrum format, we can use the following Python code:
import binascii
chain_code_hex = “chain code”
chain_code_bytes = binascii.unhexlify(chain_code_hex)
chain_code_electrum = binascii.hexlify(chain_code_bytes::-1).decode()
print(chain_code_electrum)
This code first converts the chain code from a string of hexadecimal characters to a bytes object, then reverses the byte order, then converts the reversed bytes back to a hexadecimal string. Finally, it prints the resulting string in Electrum format.
Step 3: Convert private key to Electrum format
Now that we have the chain code in Electrum format, we need to convert the private key to Electrum format as well. To do this, we can use the following Python code:
import binascii
private_key_hex = “private key”
private_key_bytes = binascii.unhexlify(private_key_hex)
public_key_bytes = bitcoin.public_key_from_private_key(private_key_bytes, True)
public_key_hex = binascii.hexlify(public_key_bytes).decode()
public_key_hash = bitcoin.hash_160(public_key_bytes)
prefix = “80” # mainnet
extended_key_bytes = binascii.unhexlify(prefix + private_key_hex + chain_code_hex + “01”)
checksum = bitcoin.double_sha256(extended_key_bytes):8
extended_key_hex = binascii.hexlify(extended_key_bytes + checksum).decode()
print(extended_key_hex)
This code first converts the private key from a string of hexadecimal characters to a bytes object, then computes its public key, then computes the public key hash, which is used as a prefix for the Electrum private key. It then concatenates the prefix, the private key, the chain code, and a suffix of “01” to form the augmented private key. Finally, it computes a double SHA256 checksum of the augmented private key, appends the first 4 bytes of the checksum to the augmented key, and outputs the resulting hexadecimal string in Electrum format.
Conclusion
Converting Bitcoin Core’s xprv format to Electrum’s zprv format can be a useful skill for anyone who wants to switch from one wallet to another or use multiple wallets simultaneously. The process involves extracting the chain code and private key from the xprv, converting the chain code to Electrum format, and then constructing the zprv using the Electrum prefix, the private key, the chain code, and a checksum. Using the bx command line tool and the pycoin Python library, this process can be automated and made more efficient. By following the steps outlined in this guide, you can easily convert your bitcoin core xprv to Electrum zprv and start using Electrum to manage your bitcoins.
FAQs
What is the xprv format in Bitcoin Core?
The xprv format is an extended private key used in Bitcoin Core’s hierarchical deterministic (HD) wallet structure. It is the root of the private key tree and can be used to derive all other private keys in the wallet.
What is the zprv format in Electrum?
The zprv format is an extended private key used in Electrum’s hierarchical deterministic (HD) wallet structure. It is the root of the private key tree and can be used to derive all other private keys in the wallet.
Why would I want to convert an xprv to a zprv?
You may want to convert an xprv to a zprv if you want to switch from Bitcoin Core to Electrum or use both wallets simultaneously. Converting the private key format allows you to access the same wallet and funds from either wallet.
What tools can I use to convert an xprv to a zprv?
You can use a variety of tools to convert an xprv to a zprv, including the bx command-line tool and the pycoin Python library. These tools allow you to extract the chain code and private key from the xprv and then construct the zprv using the Electrum prefix, the private key, the chain code, and a checksum.
Can I convert a zprv back to an xprv?
Yes, you can convert a zprv back to an xprv using a similar process. You would need to extract the chain code and private key from the zprv, convert the chain code back to Bitcoin Core format, and then construct the xprv using the Bitcoin Core prefix, the private key, the chain code, and a checksum.
Is it safe to convert private key formats?
As long as you follow the correct process and use trusted tools, it is safe to convert private key formats. However, it is always a good idea to make backups of your wallet and private keys before making any changes or conversions.