Bitcoin Express -- an iOS thin client for bitcoin

[fingster]

Bitcoin Express
Bitcoin Express (BTC Express) is the first iOS thin client for Bitcoin transactions.

Bitcoin Express can connect you to the bitcoin network in a second without downloading any blocks or headers. Once connected, you can do transactions immediately!

Features

• Quickly and easily get up and running on bitcoin network.
• Show balance of btc in your wallet on iPhone.
• Do transactions with any other peer running Mac, Windows or Linux, etc.
• Sending and receiving of Bitcoin via Bitcoin URLs.
• Backup your wallet to your secure email.

Getting Started

Email your recieving address to others

Click and enter "My Address", choose a btc address as your recieving address, touch it. Click "email" on the popup menu, then send the recieving address to others via your Email.

Send btc to others via Bitcoin Address URL

When you received an email contains a Bitcoin Address URL, by just clicking the URL, BTC Express will automatically open and prepare to send btc to that address.

Preview
http://www.bitcoinexpress.net/images/1.png
http://www.bitcoinexpress.net/images/2.png
http://www.bitcoinexpress.net/images/3.png
http://www.bitcoinexpress.net/images/4.png
http://www.bitcoinexpress.net/images/6.png

Technical Discussion: http://forum.bitcoin.org/index.php?topic=31356.0
MIT Licensed Open Source: https://github.com/fingster/BTC-Express
UI partially based on: https://github.com/udibr/bitcoinApp
Beta version download: http://www.megaupload.com/?d=9RX93T9V

[fingster]

submitted to App Store today. 

[davout]

Great ! How do you manage to pull it off without downloading the chain ? Headers only ?
Is it open or closed source ?

[hsf_context]

Great! How does it work without downloading blocks ?

[Coaster]

The real question is.. will apple* approve the app if your using a currency not purchased through their store? Which prolly wouldn't be allowed anyway. This goes outside the realms of their EUL and ToS because its allowing you to manage a currency not apple taxed.

[samr7]

Great! How does it work without downloading blocks ?

fingster may have to correct me, but it looks like it does download blocks.  However, instead of retaining the full block database like the normal client, it retains only the wallet database, including transactions on associated addresses, and discards everything else.

Edit: Never mind, I don't have a clue.  So what's "txwithtime" ?

It's an impressive reduction of the Satoshi client by any measure.

[ttk2]

As much as i usually love to lord the superiority of Android over iPhone users, the lack of a real iPhone Bitcoin client, or even just something like this is sad and it bodes ill for Bitcoin in the real world when 30% of the smartphone market is unable to have dedicated apps. 

[jago25_98]

Let's put a bounty on for the source. I pledge a BTC

[jackjack]

Am I the only one to see that in his post?

Technical Discussion: http://forum.bitcoin.org/index.php?topic=31356.0
MIT Licensed Open Source: https://github.com/fingster/BTC-Express
UI partially based on: https://github.com/udibr/bitcoinApp
Beta version download: http://www.megaupload.com/?d=9RX93T9V

[fingster]

Great! How does it work without downloading blocks ?

fingster may have to correct me, but it looks like it does download blocks.  However, instead of retaining the full block database like the normal client, it retains only the wallet database, including transactions on associated addresses, and discards everything else.

Edit: Never mind, I don't have a clue.  So what's "txwithtime" ?

It's an impressive reduction of the Satoshi client by any measure.

It's really exciting to know someone reading my source code. Thanks, samr7.
A block contains several transactions. Few of them involve your wallet, which are useless in the view of an individual peer.  As a "selfish" client, BTC Express downloads transactions involving its own wallet but not any full block/header (even the block which contains its transactions). The server, which BTC Express connects to, stores everything as a normal peer. When BTC Express queries the server, what transactions have been done on an addresses in its client wallet, the server will send transactions involving that address by a batch of commands "txwithtime".

"txwithtime", means a transaction with its block time (the born time of the block containing the transaction). BTC Express uses the transaction's blocktime as its time and received time.

After that, BTC Express sees the global state of bitcoin network as the server does. And BTC Express can spend btc coins in its wallet immediately as a normal peer after downloading all of the blocks.

When a normal peer starts, it loads block indexes, peer addresses and wallet into its memory. The full block indexes cost lots of memory and loading time. BTC Express only need to load wallet, so it starts in seconds and costs much lower memory.
BTC Express doesn't broadcast its network address to the bitcoin network, in order to save network traffic amount for the mobile devices.

[nightwolf]

Brilliant way to reduce processing power down to iOS level. Is your "edit" of the UI open-source as well? 

[fingster]

Brilliant way to reduce processing power down to iOS level. Is your "edit" of the UI open-source as well? 

The UI program codes are going to be open source after apple's review.
However, I don't have copyright on the UI elements, including icons, background pictures, etc. I am asking their author Pottor200, see if it's OK to be open source. And that part has not been decided yet.

[nightwolf]

Brilliant way to reduce processing power down to iOS level. Is your "edit" of the UI open-source as well? 

The UI program codes are going to be open source after apple's review.
However, I don't have copyright on the UI elements, including icons, background pictures, etc. I am asking their author Pottor200, see if it's OK to be open source. And that part has not been decided yet.

Awesome and wish you all the best with App Store review.

[kangasbros]

Awesome work. Hope that it passes the App Store review.

[flyswatta]

If its not approved, will u release it in Cydia?

[andrepcg]

I installed the app and now i'll review it

the app itself is awesome! pay with btc from my iphone is great!

this is the test I made to see if it works fine:
1. sent 0.01 BTC from my windows client to my iphone
2. the 0.01 were received after the 1st confirmation
3. i'm trying to send the 0.01 BTC back to my client but i cant

The first problem is when i'm typing the amount of BTC, I don't have the dot . as decimal separator because in my country we use , as decimal separator. Using , the app tells me the amount is invalid.

The second problem is after the correct amount is input in the field (0.01), i cant send back the payment because it says Insufficient funds. My iphone account balance is 0.01 by checking Balance section.

I get something different when i input 0.0090 as amount. i get: "Error: this transaction requires a tx fee of at least 0.0005 and a relay fee of 0.001, because of its amount, complexity....."

I can only send the funds when i set the amount as 0.0085.

Why am I paying two fees? What is the relay fee?

Suggestion: When sending funds, if I set the amount to send and that amount is the total BTC I have in iphone wallet, it should accept my 0.01 as input and deduct the fees after sending. People dont want to be testing values like myself. I input 0.01 and got error, then input 0.0095 and same error, then 0.009 and different error, and finally 0.0085 and it was accepted. The app itself should calculate the fees at the end and whe dont have to be testing amounts

[UniverseMan]

I like the ideas behind the client, and I hope this app gets certified.

But please, PLEASE, fix the hideous UI. Those backgrounds have to go, at the very least because they make the icon text hard to read. The color scheme looks dirty and sickly. iOS apps typically don't have Springboard-style layouts, i.e. a "home screen" and several icons to click, they have one visible screen that can be switched to different tabs (facebook is a notable exception to this).

These are just off the top of my head. I'm sure others could supply more suggestions.

But, again, good luck. I wish you the very best with this project.

[fingster]

I installed the app and now i'll review it

the app itself is awesome! pay with btc from my iphone is great!

this is the test I made to see if it works fine:
1. sent 0.01 BTC from my windows client to my iphone
2. the 0.01 were received after the 1st confirmation
3. i'm trying to send the 0.01 BTC back to my client but i cant

The first problem is when i'm typing the amount of BTC, I don't have the dot . as decimal separator because in my country we use , as decimal separator. Using , the app tells me the amount is invalid.

The second problem is after the correct amount is input in the field (0.01), i cant send back the payment because it says Insufficient funds. My iphone account balance is 0.01 by checking Balance section.

I get something different when i input 0.0090 as amount. i get: "Error: this transaction requires a tx fee of at least 0.0005 and a relay fee of 0.001, because of its amount, complexity....."

I can only send the funds when i set the amount as 0.0085.

Why am I paying two fees? What is the relay fee?

Suggestion: When sending funds, if I set the amount to send and that amount is the total BTC I have in iphone wallet, it should accept my 0.01 as input and deduct the fees after sending. People dont want to be testing values like myself. I input 0.01 and got error, then input 0.0095 and same error, then 0.009 and different error, and finally 0.0085 and it was accepted. The app itself should calculate the fees at the end and whe dont have to be testing amounts

Thank you very much for your suggestion!
I'd work on it to calculate the max btc a client could send and give a useful tip on the max value to user.

[fingster]

I like the ideas behind the client, and I hope this app gets certified.

But please, PLEASE, fix the hideous UI. Those backgrounds have to go, at the very least because they make the icon text hard to read. The color scheme looks dirty and sickly. iOS apps typically don't have Springboard-style layouts, i.e. a "home screen" and several icons to click, they have one visible screen that can be switched to different tabs (facebook is a notable exception to this).

These are just off the top of my head. I'm sure others could supply more suggestions.

But, again, good luck. I wish you the very best with this project.

I use the Three20 framework to implement UI, so the App is fb-style like.
I will re-design the UI as soon as possible.
Thank you!

[done]

So cool