3
look here https://blockchain.info/tx/d4223672c9043c17a2775abde858778fca38b53152e165757188ab747850770e
why does address start with bc1q... ? Is it some standart?
How can I derive this value from witness?
witness script here:
2 0375E00EB72E29DA82B89367947F29EF34AFB75E8654F6EA368E0ACDFD92976B7C 03A1B26313F430C4B15BB1FDCE663207659D8CAC749A0E53D70EFF01874496FEFF 03C96D495BFDD5BA4145E3E046FEE45E84A8A48AD05BD8DBB395C011A32CF9F880 3 OP_CHECKMULTISIG
2
why does address start with
bc1q...? Is it some standard?
Yes, it's a Bech32 address, specified in BIP173.
How can I derive this value from witness?
In general, you can't.
The address defines under what conditions an output is spendable. The scriptSig or script witness gives the proof that those conditions are satisfied. If you know that a particular output is a V0 witness, then you can determine what that output was based on the input spending it (the last witness stack element is the public key). However, without knowing exactly what type of output was being spent you can't generally do so.
but how this site derive this particular value? – light_keeper – 2017-12-11T09:26:20.457
1By looking at the output being spent. – Pieter Wuille – 2017-12-11T17:53:11.653
@PieterWuille please tell how to trace transaction via blockchain.info site or any other? – D L – 2018-02-15T14:09:55.570