BIP174 PSBT test vector

Hi,

Does anyone have software that successfully parses the extended private key seed found in the BIP174 test vector? I have been implementing the test vector PSBT workflow in Rust and have everything working except I can only create the extended private key from the xpriv, I am unable to use the seed to create it?

BIP174: https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki#test-vectors

PSBT workflow in BIP174 starting at the line:

  "The private keys in the tests below are derived from the following master private key:"

xpriv:

  tprv8ZgxMBicQKsPd9TeAdPADNnSyH9SSUUbTVeFszDE23Ki6TBB5nCefAdHkK8Fm3qMQR6sHwA56zqRmKmxnHk37JkiFzvncDqoKmPWubu7hDF

seed:

  cUkG8i1RFfWGWy5ziR11zJ5V4U4W3viSFCfyJmZnvQaUsd1xuF3T

I've tried decoding it as base64 and as base58.

Thanks in advance, Tobin.

The seed is encoded as a WIF private key. Decoding as WIF will result in the 32 byte seed that can be used as specified in BIP 32.

Andrew

-------- Original Message -------- On Apr 5, 2022, 6:55 PM, Tobin Harding via bitcoin-dev wrote:

> Hi,
>
> Does anyone have software that successfully parses the extended private key seed
> found in the BIP174 test vector? I have been implementing the test vector PSBT
> workflow in Rust and have everything working except I can only create the
> extended private key from the xpriv, I am unable to use the seed to create it?
>
> BIP174: https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki#test-vectors
>
> PSBT workflow in BIP174 starting at the line:
>
> "The private keys in the tests below are derived from the following master private key:"
>
> xpriv:
>
> tprv8ZgxMBicQKsPd9TeAdPADNnSyH9SSUUbTVeFszDE23Ki6TBB5nCefAdHkK8Fm3qMQR6sHwA56zqRmKmxnHk37JkiFzvncDqoKmPWubu7hDF
>
> seed:
>
> cUkG8i1RFfWGWy5ziR11zJ5V4U4W3viSFCfyJmZnvQaUsd1xuF3T
>
> I've tried decoding it as base64 and as base58.
>
> Thanks in advance,
> Tobin.
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists•linuxfoundation•org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev

On Tue, Apr 05, 2022 at 11:21:17PM +0000, Achow101 wrote:

> The seed is encoded as a WIF private key. Decoding as WIF will result in the 32 byte seed that can be used as specified in BIP 32.

Thanks fro the response Andrew, works as you say!

I am totally _not_ surprised that I was unable to work this out, for future reference is there anything about those 52 characters from which I should have been able to tell it is a WIF private key? Why is the seed not just the 32 bytes of seed data?

Thanks for you time, Tobin.