What would be a rational subkey depth to use so that my address is infeasible to locate via a systematic search? Using pycoin.

ku &lt;ext_pri_key&gt; -s 1/4/6/2/8/4/2/5.......


How many levels deep into the tree would I need to go (using only single digits) before it would be infeasible for an attacker to find it using a systematic search.

Twenty levels deep I thought would be adequate:

10**20 = 100000000000000000000


I know there are more effictive ways to obscure your address but I'm interested in this particular use case.

Thanks.
It's a bit strange to use single digits for the entire HD path since the BIP32 spec allows you to pick numbers up to 2^31 (non-hardened). BIP32 key derivation is largely using SHA512. Current ASICS for SHA256 can calculate about 10 trillion SHA256's per second, so about 160 quintillion hash operations in about 6 months. Assuming an ASIC can be built with roughly the same hashing power, you would need to go about 20 levels deep to force a machine like that to find your address in about 6 months. Of course, more machines mean faster cracking.

A far simpler solution would be to use the entire space of each level instead of just 10. 3 levels then would be plenty (~10^28)