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cruzbit

A simple decentralized peer-to-peer ledger implementation

Build Status

cruzbit is very similar to bitcoin with the following notable differences:

  • Newer crypto - The Ed25519 signature system is used for signing transactions. This system has a number of nice properties to protect users from security risks present with naive usage of ECDSA. The 256-bit version of the SHA-3 hashing algorithm is used for all hashing operations in the application, including the proof-of-work function but excluding hashing performed internally by the signature system. It's reported to be blazing fast when implemented in hardware. NaCl Secretbox is used to encrypt wallet private keys (not part of the protocol.)
  • Simplified transaction format - No inputs and outputs. Just public key sender and receiver with a time, amount, explicit fee, memo field, pseudo-random nonce, series and signature. The series is incremented network-wide roughly once a week based on block height to allow for pruning transaction history. Also included are 2 optional fields for specifying maturity and expiration, both at a given block height.
  • No UTXO set - This is a consequence of the second point. It considerably simplifies ledger construction and management as well as requires a wallet to know only about its public key balances and the current block height. It also allows the ledger to map more directly to the well-understood concept of a double-entry bookkeeping system. In cruzbit, the sum of all public key balances must equal the issuance at the current block height. This isn't the first ledger to get rid of the UTXO set model but I think we do it in a uniquely simple way.
  • No scripting - This is another consequence of the second point. Signatures are simply signatures and not tiny scripts. It's a bit simpler and arguably safer. It does limit functionality, e.g. there is no native notion of a multi-signature transaction, however, depending on your needs, you can come close to accomplishing that using mechanisms external to cruzbit.
  • No fixed block size limit - Since transactions in cruzbit are more-or-less fixed size we cap blocks by transaction count instead, with the initial limit being 10,000 transactions. This per-block transaction limit increases with "piecewise-linear-between-doublings growth." This means the limit doubles roughly every 2 years by block height and increases linearly between doublings up until a hard limit of 2,147,483,647. This was directly inspired by BIP 101. We use block height instead of time since another change in cruzbit is that all block headers contain the height (as well as the total cumulative chain work.)
  • Reference implementation is in Go - Perhaps more accessible than C++. Hopefully it makes blockchain programming a bit easier to understand and attracts a wider variety of developer interest.
  • Web-friendly peer protocol - Peer communication is via secure WebSockets. And the peer protocol and all primitives are structured in JSON. This should make working with the protocol easy for just about every modern development environment.

Why does cruzbit exist?

I noticed most people focusing on making more complex ledgers capable of executing "smart" contracts and/or crypto-magically obscuring transaction details and such. And I think those projects are pretty cool, but I'd always wanted to attempt to do the opposite and implement the simplest decentralized ledger I possibly could given lessons learned from bitcoin. I think that's what cruzbit is. Anything that I thought wasn't strictly necessary in bitcoin, or was otherwise weird, I got rid of. I wanted the design to be conceptually simple and extremely developer-friendly. I finally had some personal time on my hands so I decided, why not. And now cruzbit exists.

Warning

cruzbit is experimental alpha-quality software. There may be bugs.

Getting started mining

If you missed out on the opportunity to mine other cryptocurrencies you could give cruzbit a try!

  1. Install Go
  2. Install the wallet
  3. Run the wallet and issue a newkey command. Record the public key.
  4. Install the client
  5. Run the client using the public key from step 4. as the -pubkey argument.

Complete steps for installation of Go and the cruzbit binaries on Linux can be found here.

Like bitcoin, any blocks you mine will need to have an additional 100 blocks mined on top of them prior to the new cruzbits being applied to your balance. This is to mitigate a potentially poor user experience in the case of honest blockchain reorganizations.

Also note, instead of mining with a single public key, you can use the wallet to generate many keys and dump the public keys to a text file which the client will accept as a -keyfile argument. The wallet commands to do this are genkeys and dumpkeys.

Not interested in mining but want to play with cruzbit?

No problem! Post a public key as a comment in this thread and I'll send you some! Offer limited while supplies last :)

Note that you can run the client with -numminers 0 so that it can function as your wallet peer.

Discussion