CoreBitcoin is an implementation of Bitcoin protocol in Objective-C. When it is completed, it will let you create an application that acts as a full Bitcoin node. You can encode/decode addresses, apply various hash functions, sign and verify messages, parse some transactions and scripts, and detect common transaction types. Support for blocks and script evaluation is still in progress.

Due to "all or nothing" nature of blockchain, CoreBitcoin must perfectly match implementation of BitcoinQT ("Satoshi client"), including all its features, oddities and bugs. If you come across things that CoreBitcoin does differently from BitcoinQT, this might be a subtle bug and should be investigated.

Whenever counterintuitive things happen, I try to provide an accurate documentation to at least explain that we are aware of it (even if don't always know why it was done that way). If you read the source and lack documentation for some weird code, please add a "WTF?" comment right there and send me a pull request. Or create an issue on Github.

Clone this repo and make sure you can run "UnitTests" target. It is a simple command-line app that runs a bunch of asserts. If nothing fails, the program silently exits.

If it works well, add this repo as a submodule to your project. Then add all source files, OpenSSL headers, libcrypto.a and libssl.a.

In your project settings, add $(SRCROOT)/CoreBitcoin/openssl/include to "Headers Search Paths" and $(SRCROOT)/CoreBitcoin/openssl/lib in "Library Search Paths".

If this sounds cumbersome, there is a bounty for creating a CoreBitcoin.framework to simplify integration process.

• Universal OpenSSL libraries. Or as a part of a build process.
• Universal CoreBitcoin.framework bundled with OpenSSL inside.
• Full transaction support.
• Full blockchain support.
• BitcoinQT wallet reader.
• Blockchain.info wallet reader.
• Unit tests for EC sign/verify.
• Unit tests for transaction parsing/serialization.
• Modern unit test suite.
• Security analysis. Do we use truly random numbers? Do we sign things correctly? Do we have buffer overflows? And so on.
• Example of creating a transaction given some txouts.
• Example of verifying a transaction.

The only external dependency is OpenSSL (used for Bignum, ECC and RIPEMD160). OpenSSL source is stored in this repo and is built with update_openssl.sh script. OpenSSL binaries are OSX-only and committed in the repo. This is far from perfect and binary does not support iOS architectures. This will be fixed in the future.

Ideally, we wouldn't require OpenSSL at all, but keep in mind that BitcoinQT uses OpenSSL and some of its quirks are now a part of the protocol. So if you are going to reimplement ECC, it must be bug-to-bug compatible with OpenSSL implementation.

• 1 BTC for building CoreBitcoin.framework with support for x86_64, armv7, armv7s. OpenSSL should be bundled inside. [@oleganza]
• 0.2 BTC for a CocoaPod. OpenSSL should be bundled automatically (or as a dependency). [@oleganza]

To add your own bounty, add a line here (or edit an existing one), make a pull request and donate to the address below. Your donation will be reserved for that bounty only. I will contact you to check if the implementation is acceptable before paying out.

Feel free to open issues, drop me pull requests or contact me to discuss how to do things.

Code style: follow existing style and use 4 spaces instead of tabs. There's no line width limit.

Email: [email protected]

Twitter: @oleganza

Please send your donations here: 1CBtcGivXmHQ8ZqdPgeMfcpQNJrqTrSAcG.

All funds will be used only for bounties to fix stuff. Every withdrawal from this address will be documented.

You can also donate for a specific bounty. The amount will be reserved for that bounty and listed above.

Released under the WTFPL except for OpenSSL. It is not MIT License because no one reads your legalese anyway and it only adds burden. Instead, you are encouraged to donate money for development.