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docs/guide/basecoin-basics.md
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# Basecoin Basics
Here we explain how to get started with a simple Basecoin blockchain, and how to send transactions between accounts using the `basecoin` tool.
## Install
Make sure you have [basecoin installed](install.md).
You will also need to [install tendermint](https://tendermint.com/intro/getting-started/download).
## Initialization
Basecoin is an ABCI application that runs on Tendermint, so we first need to initialize Tendermint:
```
tendermint init
```
This will create the necessary files for a single Tendermint node in `~/.tendermint`.
If you had previously run tendermint, make sure you reset the chain
(note this will delete all chain data, so back it up if you need it):
```
tendermint unsafe_reset_all
```
Now we need some initialization files for basecoin.
We have included some defaults in the basecoin directory, under `data`.
For purposes of convenience, change to that directory:
```
cd $GOPATH/src/github.com/tendermint/basecoin/data
```
The directory contains a genesis file and two private keys.
You can generate your own private keys with `tendermint gen_validator`,
and construct the `genesis.json` as you like.
## Start
Now we can start basecoin:
```
basecoin start --in-proc
```
This will initialize the chain with the `genesis.json` file from the current directory. If you want to specify another location, you can run:
```
basecoin start --in-proc --dir PATH/TO/CUSTOM/DATA
```
Note that `--in-proc` stands for "in process", which means
basecoin will be started with the Tendermint node running in the same process.
To start Tendermint in a separate process instead, use:
```
basecoin start
```
and in another window:
```
tendermint node
```
In either case, you should see blocks start streaming in!
## Send transactions
Now we are ready to send some transactions.
If you take a look at the `genesis.json` file, you will see one account listed there.
This account corresponds to the private key in `priv_validator.json`.
We also included the private key for another account, in `priv_validator2.json`.
Let's check the balance of these two accounts:
```
basecoin account 0xD397BC62B435F3CF50570FBAB4340FE52C60858F
basecoin account 0x4793A333846E5104C46DD9AB9A00E31821B2F301
```
The first account is flush with cash, while the second account doesn't exist.
Let's send funds from the first account to the second:
```
basecoin sendtx --to 0x4793A333846E5104C46DD9AB9A00E31821B2F301 --amount 10
```
By default, the CLI looks for a `priv_validator.json` to sign the transaction with,
so this will only work if you are in the `$GOPATH/src/github.com/tendermint/basecoin/data`.
To specify a different key, we can use the `--from` flag.
Now if we check the second account, it should have `10` coins!
```
basecoin account 0x4793A333846E5104C46DD9AB9A00E31821B2F301
```
We can send some of these coins back like so:
```
basecoin sendtx --to 0xD397BC62B435F3CF50570FBAB4340FE52C60858F --from priv_validator2.json --amount 5
```
Note how we use the `--from` flag to select a different account to send from.
If we try to send too much, we'll get an error:
```
basecoin sendtx --to 0xD397BC62B435F3CF50570FBAB4340FE52C60858F --from priv_validator2.json --amount 100
```
See `basecoin sendtx --help` for additional details.
## Plugins
The `sendtx` command creates and broadcasts a transaction of type `SendTx`,
which is only useful for moving tokens around.
Fortunately, Basecoin supports another transaction type, the `AppTx`,
which can trigger code registered via a plugin system.
For instance, we implemented a simple plugin called `counter`,
which just counts the number of transactions it processed.
To run it, kill the other processes, run `tendermint unsafe_reset_all`, and then
```
basecoin start --in-proc --counter-plugin
```
Now in another window, we can send transactions with:
```
TODO
```
## Next steps
1. Learn more about [Basecoin's design](basecoin-design.md)
1. Make your own [cryptocurrency using Basecoin plugins](example-counter.md)
1. Learn more about [plugin design](plugin-design.md)
1. See some [more example applications](more-examples.md)
1. Learn how to use [InterBlockchain Communication (IBC)](ibc.md)
1. [Deploy testnets](deployment.md) running your basecoin application.
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## Deployment
Up until this point, we have only been testing the code as a stand-alone abci app, which is nice for developing, but it is no blockchain. Just a blockchain-ready application.
This section will demonstrate how to launch your basecoin-based application along with a tendermint testnet and initialize the genesis block for fun and profit.
**TODO** Maybe we link to a blog post for this???
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Rigel explains how to build your own basecoin-based app
docs/guide/ibc.md
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# InterBlockchain Communication with Basecoin
One of the most exciting elements of the Cosmos Network is the InterBlockchain Communication (IBC) protocol,
which enables interoperability across different blockchains.
The simplest example of using the IBC protocol is to send a data packet from one blockchain to another.
We implemented IBC as a basecoin plugin.
and here we'll show you how to use the Basecoin IBC-plugin to send a packet of data across blockchains!
Please note, this tutorial assumes you are familiar with [Basecoin plugins](/docs/guide/plugin-design.md)
and with the [Basecoin CLI](/docs/guide/basecoin-basics), but we'll explain how IBC works.
The IBC plugin defines a new set of transactions as subtypes of the `AppTx`.
The plugin's functionality is accessed by setting the `AppTx.Name` field to `"IBC"`, and setting the `Data` field to the serialized IBC transaction type.
We'll demonstrate exactly how this works below.
## IBC
Let's review the IBC protocol.
The purpose of IBC is to enable one blockchain to function as a light-client of another.
Since we are using a classical Byzantine Fault Tolerant consensus algorithm,
light-client verification is cheap and easy:
all we have to do is check validator signatures on the latest block,
and verify a merkle proof of the state.
In Tendermint, validators agree on a block before processing it. This means
that the signatures and state root for that block aren't included until the
next block. Thus, each block contains a field called `LastCommit`, which
contains the votes responsible for committing the previous block, and a field
in the block header called `AppHash`, which refers to the merkle root hash of
the application after processing the transactions from the previous block. So,
if we want to verify some state from height H, we need the signatures and root
hash from the header at height H+1.
Unlike Proof-of-Work, the light-client protocol does not need to download and
check all the headers in the blockchain - the client can always jump straight
to the latest header available, so long as the validator set has not changed
much. If the validator set is changing, the client needs to track these
changes, which requires downloading headers for each block in which there is a
significant change. Here, we will assume the validator set is constant, and
postpone handling validator set changes for another time.
Now we can describe exactly how IBC works.
Suppose we have two blockchains, `chain1` and `chain2`, and we want to send some data from `chain1` to `chain2`.
We need to do the following:
```
1. Register the details (ie. chain ID and genesis configuration) of `chain1` on `chain2`
2. Within `chain1`, broadcast a transaction that creates an outgoing IBC packet destined for `chain2`
3. Broadcast a transaction to `chain2` informing it of the latest state (ie. header and commit signatures) of `chain1`
4. Post the outgoing packet from `chain1` to `chain2`, including the proof that
it was indeed committed on `chain1`. Note `chain2` can only verify this proof
because it has a recent header and commit.
```
Each of these steps involves a separate IBC transaction type. Let's take them up in turn.
### IBCRegisterChainTx
The `IBCRegisterChainTx` is used to register one chain on another.
It contains the chain ID and genesis configuration of the chain to register:
```
type IBCRegisterChainTx struct {
BlockchainGenesis
}
type BlockchainGenesis struct {
ChainID string
Genesis string
}
```
This transaction should only be sent once for a given chain ID, and successive sends will return an error.
### IBCUpdateChainTx
The `IBCUpdateChainTx` is used to update the state of one chain on another.
It contains the header and commit signatures for some block in the chain:
```
type IBCUpdateChainTx struct {
Header tm.Header
Commit tm.Commit
}
```
In the future, it needs to be updated to include changes to the validator set as well.
Anyone can relay an `IBCUpdateChainTx`, and they only need to do so as frequently as packets are being sent or the validator set is changing.
### IBCPacketCreateTx
The `IBCPacketCreateTx` is used to create an outgoing packet on one chain.
The packet itself contains the source and destination chain IDs,
a sequence number (ie. an integer that increments with every message sent between this pair of chains),
a packet type (eg. coin, data, etc.),
and a payload.
```
type IBCPacketCreateTx struct {
Packet
}
type Packet struct {
SrcChainID string
DstChainID string
Sequence uint64
Type string
Payload []byte
}
```
We have yet to define the format for the payload, so, for now, it's just arbitrary bytes.
One way to think about this is that `chain2` has an account on `chain1`.
With a `IBCPacketCreateTx` on `chain1`, we send funds to that account.
Then we can prove to `chain2` that there are funds locked up for it in it's
account on `chain1`.
Those funds can only be unlocked with corresponding IBC messages back from
`chain2` to `chain1` sending the locked funds to another account on
`chain1`.
### IBCPacketPostTx
The `IBCPacketPostTx` is used to post an outgoing packet from one chain to another.
It contains the packet and a proof that the packet was committed into the state of the sending chain:
```
type IBCPacketPostTx struct {
FromChainID string // The immediate source of the packet, not always Packet.SrcChainID
FromChainHeight uint64 // The block height in which Packet was committed, to check Proof
Packet
Proof *merkle.IAVLProof
}
```
The proof is a merkle proof in an IAVL tree, our implementation of a balanced, Merklized binary search tree.
It contains a list of nodes in the tree, which can be hashed together to get the Merkle root hash.
This hash must match the `AppHash` contained in the header at `FromChainHeight + 1`
- note the `+ 1` is necessary since `FromChainHeight` is the height in which the packet was committed,
and the resulting state root is not included until the next block.
### IBC State
Now that we've seen all the transaction types, let's talk about the state.
Each chain stores some IBC state in its merkle tree.
For each chain being tracked by our chain, we store:
```
- Genesis configuration
- Latest state
- Headers for recent heights
```
We also store all incoming (ingress) and outgoing (egress) packets.
The state of a chain is updated every time an `IBCUpdateChainTx` is committed.
New packets are added to the egress state upon `IBCPacketCreateTx`.
New packets are added to the ingress state upon `IBCPacketPostTx`,
assuming the proof checks out.
## Merkle Queries
The Basecoin application uses a single Merkle tree that is shared across all its state,
including the built-in accounts state and all plugin state. For this reason,
it's important to use explicit key names and/or hashes to ensure there are no collisions.
We can query the Merkle tree using the ABCI Query method.
If we pass in the correct key, it will return the corresponding value,
as well as a proof that the key and value are contained in the Merkle tree.
The results of a query can thus be used as proof in an `IBCPacketPostTx`.
## Try it out
Now that we have all the background knowledge, let's actually walk through the tutorial.
Make sure you have installed
[tendermint](https://tendermint.com/intro/getting-started/download) and
[basecoin](/docs/guide/install.md).
Now let's start the two blockchains.
In this tutorial, each chain will have only a single validator,
where the initial configuration files are already generated.
Let's change directory so these files are easily accessible:
```
cd $GOPATH/src/github.com/tendermint/basecoin/demo
```
The relevant data is now in the `data` directory.
We can start the two chains as follows:
```
TMROOT=./data/chain1/tendermint tendermint node &> chain1_tendermint.log &
basecoin start --ibc-plugin --dir ./data/chain1/basecoin &> chain1_basecoin.log &
```
and
```
TMROOT=./data/chain2/tendermint tendermint node --node_laddr tcp://localhost:36656 --rpc_laddr tcp://localhost:36657 --proxy_app tcp://localhost:36658 &> chain2_tendermint.log &
basecoin start --address tcp://localhost:36658 --ibc-plugin --dir ./data/chain2/basecoin &> chain2_basecoin.log &
```
Note how we refer to the relevant data directories. Also note how we have to set the various addresses for the second node so as not to conflict with the first.
We can now check on the status of the two chains:
```
curl localhost:46657/status
curl localhost:36657/status
```
If either command fails, the nodes may not have finished starting up. Wait a couple seconds and try again.
Once you see the status of both chains, it's time to move on.
In this tutorial, we're going to send some data from `test_chain_1` to `test_chain_2`.
For the sake of convenience, let's first set some environment variables:
```
export CHAIN_ID1=test_chain_1
export CHAIN_ID2=test_chain_2
export CHAIN_FLAGS1="--chain_id $CHAIN_ID1 --from ./data/chain1/basecoin/priv_validator.json"
export CHAIN_FLAGS2="--chain_id $CHAIN_ID2 --from ./data/chain2/basecoin/priv_validator.json --node tcp://localhost:36657"
```
Let's start by registering `test_chain_1` on `test_chain_2`:
```
basecoin ibc --amount 10 $CHAIN_FLAGS2 register --chain_id $CHAIN_ID1 --genesis ./data/chain1/tendermint/genesis.json
```
Now we can create the outgoing packet on `test_chain_1`:
```
basecoin ibc --amount 10 $CHAIN_FLAGS1 packet create --from $CHAIN_ID1 --to $CHAIN_ID2 --type coin --payload 0xDEADBEEF --sequence 1
```
Note our payload is just `DEADBEEF`.
Now that the packet is committed in the chain, let's get some proof by querying:
```
basecoin query ibc,egress,$CHAIN_ID1,$CHAIN_ID2,1
```
The result contains the latest height, a value (ie. the hex-encoded binary serialization of our packet),
and a proof (ie. hex-encoded binary serialization of a list of nodes from the Merkle tree) that the value is in the Merkle tree.
If we want to send this data to `test_chain_2`, we first have to update what it knows about `test_chain_1`.
We'll need a recent block header and a set of commit signatures.
Fortunately, we can get them with the `block` command:
```
basecoin block <height>
```
where `<height>` is the height returned in the previous query.
Note the result contains both a hex-encoded and json-encoded version of the header and the commit.
The former is used as input for later commands; the latter is human-readable, so you know what's going on!
Let's send this updated information about `test_chain_1` to `test_chain_2`:
```
basecoin ibc --amount 10 $CHAIN_FLAGS2 update --header 0x<header>--commit 0x<commit>
```
where `<header>` and `<commit>` are the hex-encoded header and commit returned by the previous `block` command.
Now that `test_chain_2` knows about some recent state of `test_chain_1`, we can post the packet to `test_chain_2`,
along with proof the packet was committed on `test_chain_1`. Since `test_chain_2` knows about some recent state
of `test_chain_1`, it will be able to verify the proof!
```
basecoin ibc --amount 10 $CHAIN_FLAGS2 packet post --from $CHAIN_ID1 --height <height + 1> --packet 0x<packet> --proof 0x<proof>
```
Here, `<height + 1>` is one greater than the height retuned by the previous `query` command, and `<packet>` and `<proof>` are the
`value` and `proof` returned in that same query.
Tada!
## Conclusion
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# Install
We use glide for dependency management. The prefered way of compiling from source is the following:
```
go get -d github.com/tendermint/basecoin/cmd/basecoin
cd $GOPATH/src/github.com/tendermint/basecoin
make get_vendor_deps
make install
```
This will create the `basecoin` binary in `$GOPATH/bin`.
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## Mintcoin
You just read about the amazing [plugin system](https://github.com/tendermint/basecoin/blob/develop/Plugins.md), and want to use it to print your own money. Me too! Let's get started with a simple plugin extension to basecoin, called [mintcoin](./mintcoin/README.md). This plugin lets you register one or more accounts as "central bankers", who can unilaterally issue more currency into the system. It also serves as a simple test-bed to see how one can not just build a plugin, but also take advantage of existing codebases to provide a simple cli to use it.
## Financial Instruments
Sure, printing money and sending it is nice, but sometimes I don't fully trust the guy at the other end. Maybe we could add an escrow service? Or how about options for currency trading, since we support multiple currencies? No problem, this is also just a plugin away. Checkout our [trader application](./trader).
**Running code, still WIP**
## IBC
Now, let's hook up your personal crypto-currency with the wide world of other currencies, in a distributed, proof-of-stake based exchange. Hard, you say? Well half the work is already done for you with the [IBC, InterBlockchain Communication, plugin](./ibc.md). Now, we just need to get cosmos up and running and time to go and trade.
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# Basecoin Plugins
Basecoin is an extensible cryptocurrency module.
Each Basecoin account contains a ED25519 public key,
a balance in many different coin denominations,
and a strictly increasing sequence number for replay protection (like in Ethereum).
Accounts are serialized and stored in a merkle tree using the account's address as the key,
where the address is the RIPEMD160 hash of the public key.
Sending tokens around is done via the `SendTx`, which takes a list of inputs and a list of outputs,
and transfers all the tokens listed in the inputs from their corresponding accounts to the accounts listed in the output.
The `SendTx` is structured as follows:
```
type SendTx struct {
Gas int64 `json:"gas"` // Gas
Fee Coin `json:"fee"` // Fee
Inputs []TxInput `json:"inputs"`
Outputs []TxOutput `json:"outputs"`
}
type TxInput struct {
Address []byte `json:"address"` // Hash of the PubKey
Coins Coins `json:"coins"` //
Sequence int `json:"sequence"` // Must be 1 greater than the last committed TxInput
Signature crypto.Signature `json:"signature"` // Depends on the PubKey type and the whole Tx
PubKey crypto.PubKey `json:"pub_key"` // Is present iff Sequence == 0
}
type TxOutput struct {
Address []byte `json:"address"` // Hash of the PubKey
Coins Coins `json:"coins"` //
}
type Coins []Coin
type Coin struct {
Denom string `json:"denom"`
Amount int64 `json:"amount"`
}
```
Note it also includes a field for `Gas` and `Fee`. The `Gas` limits the total amount of computation that can be done by the transaction,
while the `Fee` refers to the total amount paid in fees. This is slightly different from Ethereum's concept of `Gas` and `GasPrice`,
where `Fee = Gas x GasPrice`. In Basecoin, the `Gas` and `Fee` are independent.
Basecoin also defines another transaction type, the `AppTx`: