How to convert a WIF private key to a BIP32 extended private key I am trying to recover the extended BIP32 master private key from its extended BIP32 public key (which I already know) and a WIF private key (which I obtained by decrypting a BIP38 seed with a passphrase).

I followed the steps described in this article from Vitalik Buterin, but to use the crack_bip32_privkey function in pybitcointools, I need to have a private key in BIP32 format (not WIF). I can see how to obtain a BIP32 private master key from a BIP32 seed (with bip32_master_key), but not how to do the same from a private key in WIF format.

How can I convert the WIF Private key into a BIP 32 private key (with Python, .NET or Javascript)?
You can't. The BIP 32 extended private key format contains information which is not present in the WIF private key. The extended private key format contains the chaincode of the private key, the index, and the parent fingerprint. Those information come from the derivation of the private key itself and cannot be found elsewhere.



In order to get the parent public key, the only information that you need from the extended public key is the index of the child. This can be trivially found by simply brute forcing through all possible child indexes (2^31 - 1 indexes) until you get a master private key which has a public key that matches the parent public key, or until you have derived the correct child public key from the parent public key.

Here is code that will find you the parent private key. This does the first technique of cycling through possible parent private keys until one is found which has a public key that matches the parent public key. Note that this may be completely inefficient and may take a long time to find a key. Also note that this only works if the child key is directly derived from the parent, not some depth down in the derivation tree.

from pybitcointools.deterministic import raw_crack_bip32_privkey, bip32_deserialize, bip32_serialize, bip32_privtopub
from pybitcointools.main import decode_privkey, encode_privkey

parent_pub = 'xpub661MyMwAqRbcEnKbXcCqD2GT1di5zQxVqoHPAgHNe8dv5JP8gWmDproS6kFHJnLZd23tWevhdn4urGJ6b264DfTGKr8zjmYDjyDTi9U7iyT'
wif_key = encode_privkey(decode_privkey('KyqcQVzcp7cHEMEDHQaz5eaE5azsRHaE4ukkeqwM2vdiQwBYtxeb'), 'bin_compressed')
for i in xrange(2**31 -1):
    priv = (b'\x04\x88\xAD\xE4', 1, 0, i, b'', wif_key)
    pkey =  raw_crack_bip32_privkey(bip32_deserialize(parent_pub), priv)
    final_key = bip32_serialize(pkey)
    if bip32_privtopub(final_key) == parent_pub:
        print final_key
        break