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.
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