<blockquote>
  <p>why does address start with <code>bc1q...</code> ? Is it some standard?</p>
</blockquote>

<p>Yes, it's a <a href="http://bitcoin.sipa.be/bech32/demo/demo.html" rel="nofollow noreferrer">Bech32</a> address, specified in <a href="https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki" rel="nofollow noreferrer">BIP173</a>.</p>

<blockquote>
  <p>How can I derive this value from witness? </p>
</blockquote>

<p>In general, you can't.</p>

<p>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 <em>know</em> 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.</p>

CC BY-SA 3.0
2017-12-11T09:26:20.457Z
but how this site derive this particular value?
light_keeper
CC BY-SA 3.0
2018-02-15T14:09:55.570Z
@PieterWuille please tell how to trace transaction via blockchain.info site or any other?
Denis Leonov
CC BY-SA 3.0
2017-12-11T17:53:11.653Z
By looking at the output being spent.
Pieter Wuille
CC BY-SA 3.0
2017-12-11T02:04:13.190Z
2017-12-11T02:04:13.190Z
Pieter Wuille
<p>look here <a href="https://blockchain.info/tx/d4223672c9043c17a2775abde858778fca38b53152e165757188ab747850770e" rel="nofollow noreferrer">https://blockchain.info/tx/d4223672c9043c17a2775abde858778fca38b53152e165757188ab747850770e</a></p>

<p>why does address start with <code>bc1q...</code> ? Is it some standart? 
How can I derive this value from witness? </p>

<p>witness script here: </p>

<p><code>2 0375E00EB72E29DA82B89367947F29EF34AFB75E8654F6EA368E0ACDFD92976B7C 03A1B26313F430C4B15BB1FDCE663207659D8CAC749A0E53D70EFF01874496FEFF 03C96D495BFDD5BA4145E3E046FEE45E84A8A48AD05BD8DBB395C011A32CF9F880 3 OP_CHECKMULTISIG</code></p>

<segregated-witness><multi-signature>
how to get address from transaction with empty ScriptSig?
light_keeper
# how to get address from transaction with empty ScriptSig?

(Asked by: username_0 on 2017-12-11)

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`

**Tags:** segregated-witness, multi-signature


---

## 1 answers

### Answer by username_1 on 2017-12-11. Score: 2 | Accepted answer

> why does address start with `bc1q...` ? Is it some standard?

Yes, it's a [Bech32](http://bitcoin.sipa.be/bech32/demo/demo.html) address, specified in [BIP173](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki).

> 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.

> **Comments:**
> **username_0**: but how this site derive this particular value?  
> **username_1**: By looking at the output being spent.  
> **username_2**: @username_1 please tell how to trace transaction via blockchain.info site or any other?  

---

