jinformatique

bitcoin

No, The EU Will Not Require ID For Every Bitcoin Transaction

The Bitcoin “security budget” error for block miners

Yes, I personally asked him and he agreed. He is fine with it. As he only writes in French on LinkedIn, I put it in English here. 

Why is quantum computing unsuitable for mining?

# What does a Bitcoin address reveal before and after a transaction?
  

Reusing a Bitcoin address is often presented as a privacy issue. However, it also raises a **real cryptographic** risk related to the security of the private key itself. The issue concerns both old P2PKH addresses and recent SegWit (bc1q...) or Taproot (bc1p...) formats: when an address is reused after having already been used to spend a UTXO, all funds associated with that same key now depend on cryptographic material exposed multiple times on the blockchain. This article explains the structural reasons for this risk, the cryptographic mechanisms involved, and the practical way to observe the public key revealed during a transaction.

  

### Exposure of the public key: a critical moment

  

Before any expenditure, a Bitcoin address **does not reveal the public key**, but only a hash:

  

```

HASH160(pubkey) = RIPEMD160(SHA-256(pubkey))

```

  

This hash offers no possibility of retrieving the public key. As long as a UTXO remains unspent, the associated key remains mathematically inaccessible.

  

As soon as a UTXO is spent:

  

- the **signature** is published,
- the **complete public key** is revealed,
- the validity of the signature is verified against this key.

  

From that moment on, the address no longer offers the same cryptographic protection: the public key is exposed to offensive analysis, and any reuse of that same key multiplies the data that can be exploited by an attacker.

  

### Where is the public key located at the time of spending?

  

The exact location depends on the type of address:

  

### P2PKH (addresses beginning with 1 or 3)

  

In **P2PKH** transactions, the public key appears:

  

- **in the scriptSig**,
- immediately after the signature,
- in hexadecimal form, usually as a compressed key (33 bytes, prefix 02 or 03) or uncompressed (65 bytes, prefix 04).

  

### P2WPKH (SegWit v0, bc1q addresses, etc.)

  

In **P2WPKH** transactions, the public key appears in the **witness**:

  

- witness[0] → signature (DER format),
- witness[1] → **compressed public key** (33 bytes, starting with 02 or 03).

  

### Taproot (P2TR, bc1p addresses, etc.)

  

**Taproot** transactions use Schnorr signatures and **x-only** public keys. The public key appears:

  

- in the **witness script**,

- usually under the “key path spending” line,

- in **x-only** format: 32 bytes (64 hex) without the 02/03 prefix.

  

### On mempool.space

  

[mempool.space](http://mempool.space/) does **not display “Public Key” in plain text**. You have to read the raw hexadecimal fields and recognize the format:

  

- **33 bytes** → compressed pubkey: starts with 02 or 03.

- **65 bytes** → uncompressed pubkey: starts with 04.

- **32 bytes** → Taproot x-only pubkey.

  

The public key is therefore always visible, but in the form of a hexadecimal field in the Inputs.

  

### Why does reuse weaken security?

  

### Revealing the public key once is not critical

  

Security relies on the difficulty of the discrete logarithm problem (ECDLP). As long as an attacker only has a single signature produced by the key:

  

- they cannot reconstruct anything,

- they have no statistical material,

- ECDLP remains intact.

  

### Revealing the same key multiple times multiplies the attack surface

  

Each UTXO expenditure associated with the same address publishes:

  

- an identical public key,

- a new, distinct signature.

  

In ECDSA (P2PKH, P2WPKH), each signature requires a random number: the **nonce k**. k must be:

  

- unique,

- unpredictable,

- perfectly generated.

  

> A flaw in the generation of k — well-documented events — allows the private key to be recovered if two signatures use the same k or correlated ks.

  

Real-world examples:

  

- Android bug in 2013,

- Faulty hardware RNG,

- Old OpenSSL libraries,

- Entropy weakness when booting a device,

- Smartcards producing biased nonces.

  

Reusing addresses **multiplies the signatures produced** by the same key → increases the probability of a cryptographic incident.

  

### Taproot improves the situation but does not eliminate it

  

Taproot uses Schnorr:

  

- deterministically derived nonce → eliminates the “same k” risk,

- more resistant linear signature structure.

  

However:

  

- the x-only key remains unique and exposed,

- multiple signatures remain exploitable for statistical analysis,

- hardware risks remain,

- post-quantum cryptography will compromise any exposed public key.

  

### Risk concentration

  

An HD wallet (BIP32) allows each UTXO to be isolated behind a different derived key. Reusing addresses negates this advantage:

  

- a bug in a single signature → compromises all UTXOs dependent on that key.

  

This is the worst possible configuration in terms of compartmentalization.

  

### What about cryptographic advances (quantum or otherwise)?

  

If an attacker gained the ability to solve ECDLP:

  

- any public key **already exposed** would become vulnerable,

- all reused addresses would be particularly fragile,

- an address that has never been spent would remain protected by HASH160.

  

Address reuse thus concentrates a future risk that the ecosystem explicitly seeks to avoid.

  

### Concrete example: key revealed in a real transaction

  

For the transaction:

  

```

7ee6745718bec9db76390f3a4390b9e7daeeb401e8c666a7b261117a6af654a1

```

  

This is a P2WPKH input. In the witness:

  

- the signature is in witness[0],

- the compressed public key is in witness[1].

  

The revealed public key is:

  

```

02174ee672429ff94304321cdae1fc1e487edf658b34bd1d36da03761658a2bb09

```

  

> Before spending: only HASH160(pubkey) was visible.

  

> After spending: the actual public key is visible, permanently.

  

### Conclusion

  

Reusing Bitcoin addresses represents a tangible cryptographic risk. It is not just a matter of poor privacy hygiene, but a structural problem: **a public key should only be exposed once**, and a signature should never be multiplied on the same key if maximum robustness is desired.

  

Current cryptographic mechanisms are robust, but experience shows that:

- implementations are never perfect,
- nonces can be biased,
- devices can lack entropy,
- hardware attacks exist,
- cryptanalysis is advancing.

  

Minimizing the exposure of public keys remains a fundamental best practice, today and tomorrow, and this starts with a simple rule: **never reuse an address that has already spent a UTXO**.

[Source](https://www.linkedin.com/in/nicolascantuinnovationresilience/)

What does a Bitcoin address reveal before and after a transaction?

tech

Why I recommend against Brave 🦁

I use LibreWolf on desktop and IronFox on android. I sync both with Firefox sync as they both are forked and hardened on a firefox base.
For a chromium based browser, I use Vivaldi.

Memes

Meme Monday - Best Bitcoin Meme Gets 5,000 CCs

Yes, even if I already know a lot of them! Have you tried this AI meme generator, pretty good.
https://supermeme.ai/text-to-meme

science

US Gvt Admits Chemtrails ✈️ Are Real (It's Worse…). Dane Wigington Reveals All

Stacker Saloon

saloon

Someone created one here, but it's not the official one, as @k00b said.
https://stacker.news/items/1279469/

Meme Monday

Yabujin_Nakamoto

![](https://m.stacker.news/116993)

![](https://m.stacker.news/116994)

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NFC tag demo to login - getportal.cc 🚪

Follow them on X:
https://x.com/PortalOnX

Check what the guys from https://getportal.cc are doing.
Cool demo with an NFC tag to login into a website or to open a door 🚪

https://youtube.com/shorts/aOwN29C-eRo

They should go live in Q1 2026 with their project, so don't hesitate to contact them to beta test.

PS: there was lots of background noise in the room, I had to use AI to remove the noise.

During PlanB Lugano Bitcoin conference, I interviewed Daniel from https://www.fairdeeds.com
His company supports circular economy in developing countries. He buys product from them and pay them in sats. Keychain and mini surf board, upcycling from used board that the kids cannot surf on it anymore with Bitcoin related backstreet art from StreetCyber from Barcelona.

Check it out.
https://youtube.com/shorts/VO_dn5oH9d0

I personally signed this board.
![](https://m.stacker.news/115201)

What is Fairdeeds doing in Bitcoin? 🤝

Travel

Live Updates: Hurricane Melissa Damage Emerging in Jamacia and Cuba

Cje95

No it will only take 5 years, and the hurricane has been planned with weather and climate controle for Jamaica Vision 2030. See for yourself. 


https://www.facebook.com/reel/1103294135096417 
https://www.facebook.com/reel/1866007997276364
https://www.facebook.com/reel/1159983032240800

https://peggyhall.substack.com/p/hurricane-melissa-clears-path-for

My take on Plan₿ Conference Lugano 2025 🎟️🇨🇭

No. I was looking for the Bitcoin cap, but they had many others not the one with the Bitcoin logo.
I got 2 caps from pubkey and tether for participating in there survey. 

### Train Travel
I came by train with the host of @AskaBitcoiner21Questions.
I am grateful 2 years ago she recommended me to read Jimmy Song and I did with his two books, Thank God for Bitcoin and Fiat Ruins Everything. Great read!
During the travel, she started to record with some questions that will end up in the podcast.
We shared some good tips/apps to know about Bitcoin. She blew my mind when she shared the level of privacy she was using to buy Bitcoin without KYC since long ago. She takes good care of her UTXO. I was ashamed because I became complacent with time and to save on fees, giving my identity on every platform just to buy cheaper (fiat mentality, huh!).
When she shared with me that even using Robosats is not an option to her, because you are giving your IBAN to another person and that's a nogo, I was shocked. I have to review my privacy strategy of buying Bitcoin.

![](https://m.stacker.news/114528)

Arriving in the evening, we got our badge and tote bag (what a nice one) to avoid the giant queue there was during next morning. Some spend half an hour just to complete registration when arriving before 9am.

![](https://m.stacker.news/114529)

![](https://m.stacker.news/114531)

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So Friday, I was all excited to follow the many talks given in 4 different rooms. The Bitcoin couple opened the floor telling us that for this 4th edition, we were 4000 participants, compared to 2800 last year, and 1000 at the first one.
The organizers did a really great job compared to last year. They made 2 rooms bigger for the talks, and the networking area was moved to the tent outside. The PlanB Forum apps is really well-made to connect with other bitcoiners and to network easily.


Over the 2 days, during breaks, we went in the city to eat nearby. At each restaurant, when it was time of paying, I asked the manager what do they do with the Bitcoins when people pay this way. Most of them said they convert it back to CHF, because they have no time to look more into Bitcoin. That's one reason I paid in fiat.

### SatoCash
For once, I learned how Cashu works and why it enhances privacy with Bastien Taquet's presentation.

![](https://m.stacker.news/114530)

### Mining Free ebook
One of the talk I liked the most is Kristian Csepcsar talking about mining. This guy is so dynamic, and with so much experience, he captivates well the audience with his anecdotes. I got his book: the ultimate Bitcoin Mining Guide! You can download a free copy by following his X (https://x.com/KristianCsep)

![](https://m.stacker.news/114533)

![](https://m.stacker.news/114534)


### Uncle Rockstar Dev
The evening I ran into Uncle Rockstar Dev, he gave me an NFC card with his picture on it, and when you tap it to your phone, the eyes flashes red like it's doing the laser eye thing, so freaking cool.

![](https://m.stacker.news/114536)

### Rock'n'roll
The evening ambiance with Satoshi Rockamoto was rock'n'roll and even better with a Jagermeister drink a friend offered me.
I was impressed with Joe Nakamoto playing the guitar! I won't share any video has Bitcoiner like to be kept private.


### Massmux
Massmux was giving a talk on his experience with Lightning node. You can check out his cool website on the subject:
Running a Lightning node in a flash
NIMBLENODE: LIT, neutrino, LND for making all fast and simple
https://massmux.org/p/running-a-lightning-node-in-a-flash


### Spam mitigation: the debate
Saturday, I attended the debate : Spam mitigation between Peter Todd and Jimmy Song. What side are you on, by the way? Let's say I just don't like Peter's sarcasm on spam, maybe he and his team did it because of the incentives or just because you can, so why not remove the spam filter right? History will show that it's an attack on Bitcoin, and it started this year.

![](https://m.stacker.news/114537)


### LIVE WAGMI stage recording
As I knew the WAGMI stage was fully recorded, and later available online, I strategized to go to other rooms to listen talks.
Even knowing there is recording available, the tricky part is to find some time to watch them. When there is no urgency, there is no need to watch it, even if the subject is interesting. Are you going to watch some of it?

DAY 1 - WAGMI Stage – Lugano Plan ₿ Forum 2025 | Live from Lugano 🇨🇭 
https://rumble.com/v70mlfs-wagmi-stage-lugano-plan-forum-2025-live-from-lugano-.html

DAY 2 - WAGMI Stage – Lugano Plan ₿ Forum 2025 | Live from Lugano 🇨🇭 
https://rumble.com/v70qav2-wagmi-stage-lugano-plan-forum-2025-live-from-lugano-.html


🎥 Rumble Rolls Out BTC Tips for Creators
_Rumble CEO Chris Pavlovski announced at the Plan B Forum in Lugano that the online video platform has partnered with Tether to let its 51M users tip creators in BTC and stablecoins, cutting out middlemen and bank fees. The feature will launch by mid-December with support from MoonPay’s new Rumble Wallet. Pavloski says the goal is secure, decentralized payouts that empower global creators and shield them from deplatforming. Tether CEO Paolo Ardoino called the integration part of a global effort to ‘empower creators’ and ensure they ‘will not be debanked for what they say.’ Rumble’s move builds on its Bitcoin treasury, now worth about $25M._

### Bitcoin Art Gallery
The day passed so quickly, I went to the Bitcoin Art Gallery and other booths, to interview some of them.
- I interviewed Daniel from https://www.fairdeeds.com
His company supports circular economy in developing countries. He buys product from them and pay them in sats. Keychain and mini surf board, upcycling from used board that the kids cannot surf on it anymore with Bitcoin related backstreet art from StreetCyber from Barcelona.
- Alekos from https://getportal.cc with a cool demo with an NFC tag to login into a website or to open a door.

![](https://m.stacker.news/114573)


I bought a beer of Satoshi that has a winning QR code inside with sats. I have not opened it yet.

## Drone Show
I had to leave early and missed the drone show, but you can catch it up here in accelerated.

![](https://m.stacker.news/114526)

Source : https://x.com/prestonpysh/status/1982149245042893126?s=48&t=zCAWtQ7jmH5loHLohzM67A

If you want to have a look at the full version with sound, it's one YouTube.
https://www.youtube.com/watch?v=oogSuBzpQig


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