How do I properly derive a stake key from an address using Bech32?

Question

I'm trying to get a stake address from a Shelley address in Python using this library: https://pypi.org/project/bech32/

I can convert an address from bech32 to hex without issue, but I'm getting stuck grabbing the staking part (final 56 bytes) and converting that to Bech32. I keep getting a staking address that doesn't actually exist:

address_words = bech32.bech32_decode("addr1qxdvcswn0exwc2vjfr6u6f6qndfhmk94xjrt5tztpelyk4yg83zn9d4vrrtzs98lcl5u5q6mv7ngmg829xxvy3g5ydls7c76wu")

address_hexlist = bech32.convertbits(address_words[1], 5, 16)

account = ''.join([f'{c:04x}' for c in address_hexlist])[-58:-2]

btr = bytes.fromhex(account)

stake_words = bech32.convertbits(btr, 8, 5)

stakeaddr = bech32.bech32_encode("addr", stake_words)
print(stakeaddr)

Using the above, I get the correct account = 883c4532b6ac18d62814ffc7e9ca035b67a68da0ea298cc24514237f

However, I get the wrong staking address at the end: stake13q7y2v4k4svdv2q5llr7njsrtdn6drdqag5cesj9zs3h7xjwn42

The correct staking address should be: stake1uxyrc3fjk6kp343gznlu06w2qddk0f5d5r4znrxzg52zxlclk0hlq

The annoying thing is, the wrong address I get is the same as what you get trying to use https://slowli.github.io/bech32-buffer/ which makes me think I'm missing something specific that cardano does differently to the bech32 spec.

I can't use the provided bech32.exe binary because it refuses to work (even if it did work, I'd still like to get it working in python).

Answer 1

Credit to someone on Reddit who helped me with this:

Deriving the staking address requires you to manually update the header byte before bech32 encoding the hex account. All I needed to do was add e1 to the start of the account (1110 0001)

Answer 2

Maybe it is a bit late, but hope it helps.

You can use this python library PyCardano to derive the stake key.

Here is the code example:

>>> from pycardano import Address, Network

>>> addr = Address.from_primitive("addr1qxdvcswn0exwc2vjfr6u6f6qndfhmk94xjrt5tztpelyk4yg83zn9d4vrrtzs98lcl5u5q6mv7ngmg829xxvy3g5ydls7c76wu")
>>> addr2 = Address(staking_part=addr.staking_part, network=Network.MAINNET)
>>> addr2
stake1uxyrc3fjk6kp343gznlu06w2qddk0f5d5r4znrxzg52zxlclk0hlq

We first convert the address string to an Address object, addr. Then we use the staking part of the address to create a new stake address.