Get the public key given a Tx out

[qui8t]

Could someone please let me know how I can extract a public key from any given Tx output, regardless of the output type, at least including the most common types. For instance,

"vout": [
    {
        "value": 50.00000000,
        "n": 0,
        "scriptPubKey": {
            "asm": "04fa4b30422c7820c4ef979eaa39f770b32dcddc433cfd4d3040d3f2dc337e445dfd80fd4a3afbabe11e861fe30a28c5acc0f59915d9e419ffecd8ce374d46ddf5 OP_CHECKSIG",
            "desc": "pk(04fa4b30422c7820c4ef979eaa39f770b32dcddc433cfd4d3040d3f2dc337e445dfd80fd4a3afbabe11e861fe30a28c5acc0f59915d9e419ffecd8ce374d46ddf5)#rdr7xke8",
            "hex": "4104fa4b30422c7820c4ef979eaa39f770b32dcddc433cfd4d3040d3f2dc337e445dfd80fd4a3afbabe11e861fe30a28c5acc0f59915d9e419ffecd8ce374d46ddf5ac",
            "type": "pubkey"
        }
    }
],

or

"vout": [
    {
        "value": 100.00000000,
        "n": 0,
        "scriptPubKey": {
            "asm": "OP_DUP OP_HASH160 12ab8dc588ca9d5787dde7eb29569da63c3a238c OP_EQUALVERIFY OP_CHECKSIG",
            "desc": "addr(12higDjoCCNXSA95xZMWUdPvXNmkAduhWv)#zn56zju2",
            "hex": "76a91412ab8dc588ca9d5787dde7eb29569da63c3a238c88ac",
            "address": "12higDjoCCNXSA95xZMWUdPvXNmkAduhWv",
            "type": "pubkeyhash"
        }
    }
],

[joemphilips]

The first one already has uncompressed pubkey which starts from 04. Second one is pubkeyhash so you can not extract it. The actual pubkey will be included in the next tx input. So if this txo is already spent, you can check the next input, if not, you cannot get pubkey unless this is your UTXO.

[qui8t]

Two follow-up questions:

• Does NBitcoin has any parsing method that returns the pubkey? Such that it returns value from pk(value) in the first example, and returns None in the second? Because I suppose there are many different types of vout each with their unique pubkey logics, so I'm trying to avoid implementing vout-specific parsing methods and use NBitcoin instead.

• What is the correlation between pubkey and address? (as referenced in the second example)

[joemphilips]

　Does NBitcoin has any parsing method that returns the pubkey? Such that it returns value from pk(value) in the first example, and returns None in the second? Because I suppose there are many different types of vout each with their unique pubkey logics, so I'm trying to avoid implementing vout-specific parsing methods and use NBitcoin instead.

There are two ways.

1. Parse output descriptor ("desc"), something like

if (NBitcoin.Scripting.OutputDescriptor.TryParse(
        "pk(04fa4b30422c7820c4ef979eaa39f770b32dcddc433cfd4d3040d3f2dc337e445dfd80fd4a3afbabe11e861fe30a28c5acc0f59915d9e419ffecd8ce374d46ddf5)#rdr7xke8",
        NBitcoin.Network.Main,
        out var foo))
{
    var msg = (foo) switch
    {
        OutputDescriptor.PK pk when pk.PkProvider is NBitcoin.Scripting.PubKeyProvider.Const pkp => pkp.Pk,
        _ => null,
    };
}

2. Parse "hex" scirptpubkey directly

Something like

var hex = NBitcoin.Script.FromHex(
        "4104fa4b30422c7820c4ef979eaa39f770b32dcddc433cfd4d3040d3f2dc337e445dfd80fd4a3afbabe11e861fe30a28c5acc0f59915d9e419ffecd8ce374d46ddf5ac");

foreach (var op in hex.ToOps())
{
    if (op.PushData is not null)
    {
        try {
            var pk = new NBitcoin.PubKey(op.PushData);
            Console.WriteLine($"Pubkey from script is {pk}");
        } catch { }
    }
}

What is the correlation between pubkey and address? (as referenced in the second example)

https://bitcoin.stackexchange.com/questions/72184/why-is-p2pkh-used-instead-of-the-simpler-p2pk

[qui8t]

Both options are excellent, thank you!!

What is the correlation between pubkey and address? (as referenced in the second example)

https://bitcoin.stackexchange.com/questions/72184/why-is-p2pkh-used-instead-of-the-simpler-p2pk

Is there any approach in NBitcoin to return address given any tx out? (given the output type is either to address, pk, or any compatible script.)

[joemphilips]

Is there any approach in NBitcoin to return address given any tx out? (given the output type is either to address, pk, or any compatible script.)

No, p2pk does not have an address format.

https://bitcoin.stackexchange.com/questions/72194/why-dont-p2pk-scripts-have-their-own-address

[qui8t]

Would not RipeMD160(SHA256(pk)) in p2pk create the address?

[joemphilips]

that's not p2pk anymore, it is p2pkh.

[qui8t]

True, though would not the address be compatible?

My goal is to get either the address or pubkey for most types of tx outputs; and it seems getting address is more feasible than pubkey. So, I am looking for how I can use NBitcoin to return an address, or some field I can use to build address from.

I assume all the following types either have an address, or address is constructable:

• P2PK
• P2PKH;
• P2SH;
• P2WPKH;
• P2WSH.

[joemphilips]

True, though would not the address be compatible?

Not really. Please read the link that you have pasted more carefully.

I made a comment in #1220. You can close this issue I suppose.

[qui8t]

Thank you.