Minicash

A cryptocurrency without blockchain

What is Minicash?

As the title says Minicash is a cryptocurrency that doesn't use blockchain but instead uses a ledger of addresses and balances. It uses GPG asymmetric cryptography for secure communication and "voting". Voting occurs on two cases, first when a new key requests to be introduced to the ledger and second when a transaction is requested. For a key to be valid to enter the ledger a proof of work must be provided. This needs many sha256 calculations and regulates the difficulty of key creation. When a key enters the ledger, 10 new coins are created and assigned to this key.

Why to choose Minicash?

Most of the current cryptocurrencies use the blockchain which requires huge free space to dedicate in your hard disk. Running a full node is important and one way road for the security. Minicash doesn't have this problem as the ledger and GPG key's size is not big enough to be noticed. Also Minicash concentrates on simplicity. Without a blockchain no resource hungry calculations need to be done.

The big picture

Bob (as every other peer) has a ledger with the balances of all the peers in the network. How does he send 5 coins to Alice?

1. Bob takes a copy of the ledger.
2. Makes the appropriate balance change.
3. Signs it with his private key and sends it to all the peers.
4. Each peer checks for the validity of the transcaction and if he finds it valid signs the whole message with his private key and sends it back to Bob.
5. Bob collects all the data from the peers and puts them together in a new message.
6. Sends this message back to all the peers.
7. Each peer checks if the block received contains signatures from more than 66% of the total peers and if yes then the transaction is valid so the peer renews his ledger according to the transcation.  

How are coins created?

There is no mining. Coins are born every time a new GPG key fingerprint is introduced in the legder together with a proof of work. The proof of work is an integer that when sticked to the end of the fingerprint with a _ between them creates a string that its sha256 hash starts with a specified number of zeros. For example: fingerprint_proofOfWork. So each time a new key fingerprint, accompanied with proof of work, enters the ledger 10 fresh coins are added on its balance.

How to install?

Minicash has been tested working on Linux with Python 3.5 and Python 3.6

1. You can download it from Pypi. Decompress the file in a folder and run python setup.py install from that folder.
2. Alternatively you can download it straight from pip running pip3 install Minicash
3. There are alse portable executable files to use here. Download the portable zip archive and extract the binary files inside it to the /usr/local/bin folder.

Important notes:

• Using a virtualenv is strongly adviced.
• When gpg command is invoked gpg2 should run rather than gpg1.
• Requires dirmngr to be installed from your Linux distribution's repositories for Minicash to be able to download/upload keys to/from keyservers.
• Minicash uses the specific MinicashPeerServer software for network peer discovery. You will need it if you intend to use Minicash on local networks.

Components

=============

minicashd (The node's server - daemon)

(minicashPy3-5Env) aris@adesk MinicashWorld-> minicashd -h
usage: minicashd [-h] [--loglevel LOGLEVEL] [--peerserver PEERSERVER]
                 [--homedir HOMEDIR] [--nopid]
                 password

positional arguments:
  password              Common password for all the GNUPG keys

optional arguments:
  -h, --help            show this help message and exit
  --loglevel LOGLEVEL   Level of logging in file minicash.log
  --peerserver PEERSERVER
                        IP of the peer discovery server
  --homedir HOMEDIR     Directory inside which .minicash should be located

minicash (The node's command line client)

(minicashPy3-5Env) aris@adesk MinicashWorld-> minicash -h
usage: minicash [-h]
                {listpeers,getledger,introducekeytoledger,listlocalkeys,gen-pow,add-key,getbalances,getallbalances,stop,send}
                ...

positional arguments:
  {listpeers,getledger,introducekeytoledger,listlocalkeys,gen-pow,add-key,getbalances,getallbalances,stop,send}
    listpeers           List all online nodes in the network
    getledger           Print the current ledger
    introducekeytoledger
                        Introduce the key to the ledger
    listlocalkeys       List all local keys fingerprints
    gen-pow             Create proof of work
    add-key             Add existing key in the node
    getbalances         Get the balances
    getallbalances      Get the balances of all the nodes
    stop                Stop the server
    send                Pay to other key

optional arguments:
  -h, --help            show this help message and exit

quickDataGen (A script for easy and fast keys and configuration generation)

(minicashPy3-5Env) aris@adesk MinicashWorld-> quickDataGen -h
usage: quickDataGen [-h] keysnum difficulty password homedir [homedir ...]

positional arguments:
  keysnum     Number of keys to create
  difficulty  Number of zeros hash start
  password    The gpg private key password
  homedir     Directory inside which .minicash folder should be created

optional arguments:
  -h, --help  show this help message and exit

How to use?

Prerequisites:

• Decide a common password that you'll be always using for every new gpg key you will create. Let's call it "mypassword"
• Decide inside which folder you want the ".minicash" configuration folder to be placed. Let's name it "myinstallationfolderpath" (default is the linux user home folder).
• You need to do port forwarding at your router so that it sends all port 2222 incoming data to your node.
• If you run a peer discovery server on the same computer you run a server node make sure to pass the --peerserver argument with the IP and not just "localhost".
• Attention: Every path you pass to the command line must be the full path.  

The hard way:

1. Make sure you are connected to the Internet.
2. Run minicashd --homedir <myinstallationfolderpath> <mypassword> to boot the daemon.
3. Create a GPG key pair: gpg --homedir <myinstallationfolderpath>/.minicash/.gnupg --gen-key using "mypassword" when asked for password.
4. Run gpg --homedir <myinstallationfolderpath>/.minicash/.gnupg --list-keys --keyid-format long | grep -Po 'pub rsa2048/\K[A-Z0-9]*' and note down the 16 character public key fingerprint of the output. Let's call it "myfingerprint".
5. Create proof of work running minicash gen-pow 7 <myfingerprint>. Wait for a while and let's name the output "proof".
6. Add the key with the proof to minicash running minicash add-key <myfingerprint> <proof>.
7. Introduce the key to the global ledger running minicash introducekeytoledger <myfingerprint>.
8. Now you are ready to do your first transaction. You have 10 coins since your key was introduced to the ledger. Say you want to send 1.504 coins to the fingerpint 1559CBEBCB7E72B6. Run minicash send <myfingerprint> 1559CBEBCB7E72B6 1.504.
9. Congratulations! You've done your first transaction!

The lazy way:

1. Run quickDataGen 1 7 <mypassword> <myinstallationfolderpath>
2. Run minicashd --homedir <myinstallationfolderpath> <mypassword> to boot the daemon.
3. Run minicash listlocalkeys and note down your 16 character fingerprint. Let's call it "myfingerprint"
4. Follow the "The hard way" above from step 7 until the end.  

Help

On every case you can run minicash -h to list the available options. Don't hesitate to email me on arisgold29@gmail.com with "minicash" as title in case you have any questions.