I did a Bitcoin presentation today at a company where I used to work (which happens to make hardcore cryptography for big classical financial institutions) and an old colleague asked me:

"If the Satoshi white paper is above my level, where do I find a book that explains all this in layman terms?"

... and I said "Hmm... good question."

I spent several years reading + writing code and forums to get my understanding of Bitcoin, and consider myself one of the few who really understand how Bitcoin works. Bitcoin has come far, but yet, we do not have a proper piece of literature that explains how it really works.

There is a book for everything.... except Bitcoin. There must be a big opportunity waiting here.

When I search for Bitcoin on Amazon I feel ashamed.

I am running a custom node that does real-time double spend analysis. I took a look at the log file over the last few days to see what was going on now that we have a lot of focus on malleable transactions.

Note that my custom node counts mutations on the same transaction as a double spend, which it isn't.

Detected double spends by date:

2014-01-29 470
2014-01-30 460
2014-01-31 460
2014-01-29 470
2014-01-30 460
2014-01-31 0
2014-02-01 39
2014-02-02 18
2014-02-03 97
2014-02-04 918
2014-02-05 461
2014-02-06 406
2014-02-07 769
2014-02-08 1260
2014-02-09 2618
2014-02-10 14576
2014-02-11 16960
2014-02-12 393
2014-02-13 219
2014-02-14 54

Needless to say that things got hectic yesterday with 14576 "double spends" which I am pretty sure are malled transactions.

We seem to be approaching the total number of transactions which is about 60k a day. So it seems that someone is having a lot of fun.

I will be changing my software to do real malled transaction detection to get some more accurate numbers.

Edit 1: added stats for 2014-02-11
Edit 2: added stats for 2014-02-12
Edit 3: added stats for 2014-02-13
Edit 4: added stats for 2014-02-14

...when you do it like this: http://www.youtube.com/watch?v=jV-29RFU6xA

In case you didn't notice, Mycelium Bitcoin Wallet is now available in Nederlands.
We are very grateful for Martijn Wismeijer from the Bitcoin community who put a lot of time and effort into translating it.
Please help us spread the word in your country.

Mycelium Bitcoin Wallet is now available in Russian.
We (the developers) are grateful for the volunteers from the Bitcoin community who put a lot of time and effort into translating it.
Please help us spread the word in Russian speaking countries.

Mycelium Bitcoin Wallet is now available in Portuguese.
We (the developers) are grateful for the volunteers from the Bitcoin community who put a lot of time and effort into translating it.
Please help us spread the word in Portuguese speaking countries.

Mycelium Bitcoin Wallet è ora disponibile in italiano.
Gli sviluppatori sono grati a tutti i volontari che hanno messo a disposizione tempo ed energie nella traduzione.
Aiutateci anche voi a far conoscere l'applicazione nel vostro paese.

Edit: Thanks to alexrossi, who translated this message to Italian

Mycelium Bitcoin Wallet is now available in Chinese.
We (the developers) are grateful for the volunteers from the Bitcoin community who put a lot of time and effort into translating it.
Please help us spread the word in your country.

Mycelium Bitcoin Wallet is now available in Spanish.
We (the developers) are grateful for the volunteers from the Bitcoin community who put a lot of time and effort into translating it.
Please help us spread the word in Spanish speaking countries.

[If you know Portuguese or someone who does please help us out]

While we are at the final stages of releasing version 1.0 we are already looking ahead for version 1.1 where the release topic is translations.
Our initial focus is Chinese, Spanish, German, Russian, and Portuguese.
We already have volunteers for everything but Portuguese

If you know Portuguese or someone who does please help us out

To sign up send me an email at: jan.moller@gmail.com

Project forum thread: https://bitcointalk.org/index.php?topic=293472.0

On testnet I have observed output scripts that do not follow (what I consider) the basic chunking rules.

First occurrence in the testnet block chain (October 14 2013):
 Block: 0000000001fd48a0089ed98737a9212c62e7708d8ddde3aea7a9f57a138f769d
 Transaction outpoint: 4fed625bfe36c2d17d839a6407be374663ad823c2cde7073319bb51b8025a221:0
 Script bytes: 0130323066643366303435313438356531306633383837363437356630643265396130393739343 3323535343137666531393164386239636232306534306438633330303264313734633365393063 6632343339323138376131303762363437333763393733313563393239326465343137373163656 5613062323563633534353732653302ae

According to chunk decoding rules it should have 5 chunks with lengths 1, 50, 1, 57, 49. At the last chunk it goes beyond the script length. 
Chunk 1 (length  1): 0x30
Chunk 2 (length 50): 3066643366303435313438356531306633383837363437356630643265396130393739343332353 534313766653139316438
Chunk 3 (length  1): 0x62 (OP_VER)
Chunk 4 (length 57): 6362323065343064386333303032643137346333653930636632343339323138376131303762363 43733376339373331356339323932646534
Chunk 5 (length 49): 373731636565613062323563633534353732653302ae (only 22 of 49 bytes available)

According to my code it has never happened before on testnet, and never on prodnet.

On testnet it happens 3 times in block 0000000001fd48a0089ed98737a9212c62e7708d8ddde3aea7a9f57a138f769d and once in block 0000000000b6f43e05f86dfe2007107fc88ace03457294d7f74d960b239dc8bf

I was under the impression that non-standard output scripts were accepted on testnet, but that they should follow basic chunking rules.
Since bitcoind accepts those output scripts on testnet I have adapted my code to be more lax when doing script validation.

Can anyone confirm whether this can also happen on prodnet?

The Mycelium Bitcoin Wallet is a Bitcoin wallet for Android and the successor of BitcoinSpinner.
It was initially announced in the BitcoinSpinner forum thread as an early beta.

We have received a lot of great feedback over the months, which has allowed us to dramatically improve the wallet. It is now deployed on more than 2000 devices.

Overview:

• Sources available for review: https://github.com/mycelium-com/wallet
• 100% control over your private keys, they never leave your device unless you export them.
• No block chain download, installs and runs in seconds.
• Ultra fast connection to the Bitcoin network through our redundant super nodes.
• Designed for simplicity, but with unique advanced features in expert mode.

Features:

• Cold storage spending: Spend directly from paper (demo)
• Import private keys using SIPA and mini private key format (Casascius private keys) from QR-codes or clipboard
• Export private keys as QR-codes, on clipboard, and directly to printer using external SD card (demo).
• Watch-only addresses
• Key control using Active and Archive key set.
• PIN protection
• Multiple Bitcoin denominations: BTC, mBTC, and uBTC
• View your balance in 164 fiat currencies
• Switch between Bitstamp, MtGox, or weighted average when getting BTC/fiat exchange rates
• Switch between BTC/fiat when sending coins
• Switch between BTC/fiat when making a payment request
• Address book for commonly used addresses
• Transaction history with full transaction details.
• Tor connections using Orbot with SOCKS proxy
• Integrated QR-code scanner
• Share your bitcoin address using Twitter, Facebook, email ...

...and more.

apetersson and I have been working full time since April developing this wallet. We hope you like it and leave a 5 star review on Google Play.

If you want to get early access to new releases please join the Google+ group Mycelium Beta Testers

TL;DR
Try out the Mycelium Bitcoin Wallet: Google Play or direct download
The sources are published here: https://github.com/mycelium-com/wallet
We hope you like it and leave a 5 star review 

EDIT: Release notes for version 1.3.3:

v1.3.3 was released to Google Play store, github, and our site.

The list of changes from last regular release include:

* Generic scan button in the main view - Use this to quickly scan QR codes to send bitcoins. In the future, this may be used to quickly log into websites with BitID.
* Improvements to barcode scanning with flashlight toggle and autofocus setting
* Email notifications for LocalTrader - Google Push Notifications system is still kind of unreliable, and we can't fix it because it's Google servers that are having issues, so this is a fix until we figure out something better.
* Fixes and connectivity fallback for dns issues - A few days ago we had an issue where our domain name, which is pointing to our servers, was temporarily turned off by our provider while they verified that we are who we say we are. Should this happen again, wallets will switch to contacting our servers with their IP numbers directly (this is also likely temporary, until we move everything to Tor)
* Various crash fixes

We think that this will be the last feature update for the non-HD version. Stay tuned for an upcoming Mycelium HD release.

If you pull mtgox ticker data from their API you may look at old data.

It seems that when MtGox switched over to use AKAMAI for their web-fontend-cache the by accident also made akamai serve cached trade data.

The results you get by fetching: https://data.mtgox.com/api/1/BTCEUR/public/ticker
May be very different for what you get without HTTPS (http vs https): http://data.mtgox.com/api/1/BTCEUR/public/ticker

I noticed that one of my servers was using data back from August 20!
The results vary depending on which host you are using. You get various old sets depending on which DNS records your host has. On one host data.mtgos.com maps to e7476.b.akamaiedge.net while on another it maps to a23-53-216-44.deploy.static.akamaitechnologies.com, etc...

It seems that http is not cached.

I just received this email from what Gmail tells me is "theymos@bitcointalk.org via wedos.net"
This is a fraud.
Don't fall for email like that.

Hi Jan,

My name is theymos (administrator of Bitcointalk.org),

I wrote this application for a contribution to improve the forum because I believe that there are people who are interested in this forum and who are interested in the Bitcoin community.

As you well know, our servers are sometimes very slow. As a result we were forced to implement (time) protection of the registration, login, posts, search, and more.
Also lots of other stuff does not work as we would have liked, so we all like to eliminate these shortcomings.
To do this, we do not have enough funds (as you know, a forum is completely free), and therefore we ask for a contribution.

For this cotribution we set up a new address, and we'll watch the addresses from which contributions go.

CONTRIBUTOR BENEFITS
- 0.1+ BTC = Donors crown before nick (everywhere your username is shown)
- 1+ BTC = Add a trusted mark from theymos ( a dmin)
- 5+ BTC = Write your nick to the footer of forum

Each contributor is considered to be honorary member of a forum. Those user gains respect from others and will be an important figure in participation in the growth of this forum.

After submitting your contribution, please write a private message to theymos, stating the address from which you sent the payment.
Then we can apply the benefits of your user.

BTC address for donation: 1JTDTfgEixS41vqwKAu9rMHZRhujowTJ6a

Thank you on behalf of the whole community of Bitcointalk.org!

Sincerely,

theymos

I within the last 30 minutes I got four different spam mails on Bitcoin claiming to come from:

• BitPay
• GLBSE
• MtGox Support Desk
• 邱亮

Here is a sample

I guess I am not the only one.

Transaction fees are a hot topic these days as we get closer to the maximum block size. If the block size is not increased fees are bound to grow, but unfortunately many bitcoin clients (including my own BitcoinSpinner) do not handle this well. Right now I am using a fixed fee of 0.0005 for every 1000 bytes, and eventually this will not cut it.

Transaction fees are complex  (especially for end users), and for BitcoinSpinner I want a solution where the fee applied makes the transaction likely to get into the next few blocks.

Miners who use an unmodified bitcoind for mining still allow a chunk of gratis transactions with high priority, but I think this will go away due to maximizing profit, and eventually miners will look at fee/transaction-size-in-bytes (eventually considering chains of unconfirmed transactions and their associated fees, etc). So, generally speaking I believe that there will be a price measured in satoshis for getting a byte into the next block. (And not for every 1000 byte chunk as it is now)

So to me the question: How do I predict the cost of getting my transaction into the next few blocks?
Is really: How do I predict the cost of getting a byte into the next few blocks?

My half-baked thinking on this is to:
1. Look at the last 144 blocks (24 hours)
2. Filter away gratis transactions
3. Filter away the bottom 25% and top 25% transactions that include a fee (measured in fee-pr-byte)
4. Calculate f1 = my-transaction-size-in-bytes * <the average fee pr byte in the remaining transactions>
5. Calculate f2 = the fee using traditional fee mechanisms for my transaction (0.0005 pr 1000 bytes)
6. Final fee =  max(f1,f2)

(Obviously step 4 and 5 will have to iterate until a fix point is reached as the size of the transaction may be affected by the fee size.)
Step 6 is there to avoid situations where f1 < f2, and miners still use the classic fee rules

On top of this the user could configure his wallet to be:
Economic: f1 = f1 * 1/2 (get confirmed when there is room)
Normal: f1 unmodified (get confirmed at a 'normal' rate)
Priority: f1 = f1 * 2 (get confirmed quickly)

This way end users have some control over their fees/confirmation-times without having an extended math degree, plus we get a fee market going.

What do you think?

In the beginning the difficulty was very low, and generating blocks that have the genesis block as their parent can be done today in no time.
If I publish such blocks will they be accepted by the network? Or, is this prevented by checkpoints?
If they are not rejected I can spam the network with blocks at height 1 and force every node to store them in their database.

I am sitting in an airport in Denmark, and waiting for my flight to Stanstead. Looking forward to meet a lot of enthusiastic bitcoiners tonight, and have a blast. I'll try to update this thread with my impressions over the weekend.
Anybody else traveling today?

Tomorrow I am moving to the San Francisco bay area for a 3 month stay. I'll bring BitcoinSpinner along, and hopefully get time to implement a few features.
I am interested in meeting other bitcoiners while there.
What is the Bitcoin scene in Silicon Valley? Any meetups?

BitcoinSpinner has been around for some time now, and a lot has happened since it was announced back in November.
In an effort to be more open I would like to share some BitcoinSpinner stats with the community.

• Total installs to date: 816
• Active device installs: 503 (people we did not uninstall it again)
• Total installs with actual BTC in them: 303 (This is the one that really matters)

To be honest I had expected more active users when I started out. On the other hand, 300 is not bad at all, and the number is climbing slowly but steadily every day.

Since the theme for BitcoinSpinner is ease of use, and getting up and running really quickly, I expect to get a large influx of users once Bitcoin hits the next level of adoption. We are not there yet, but I am ready.

I would be very interested in getting some stats from other Bitcoin services.
So, how is it going?