Simple Transaction

Purpose

The purpose of this tutorial is to demonstrate how to manually construct a simple transaction on Minima.

We recommend going through it a couple of times to make sure you understand the process and before moving onto more complicated tutorials.

You will learn

In this tutorial you will learn:

• How to manually construct a valid transaction
• How to add inputs and outputs to a transaction
• How to add a burn to a transaction
• How to sign and post a transaction on-chain

Pre-requisites

You should have an understanding of:

• How the UTxO model works
• How the send command works

You will need:

• The latest minima.jar downloaded
• Two test nodes - one to send coins and one to receive coins.
  One of these nodes should be started from Genesis so you have 1 billion coins to play with.

There are no other dependencies.

Tutorial

1. Start two test nodes

To set up your two test nodes, open two new command prompt sessions and change directory into the folder where your minima.jar file is.

Follow the guidance here to start the nodes.

2. Create a transaction

To get more detail on any of the commands used in this tutorial, you can use help command: e.g. help command:txncreate.
The coinids and addresses in this tutorial will differ to yours.

On node 1, create a transaction called simpletxn.

txncreate id:simpletxn

You will see the following output:

txncreate id:simpletxn
{
  "command":"txncreate",
  "params":{
    "id":"simpletxn"
  },
  "status":true,
  "pending":false,
  "response":{
    "id":"simpletxn",
    "transaction":{
      "inputs":[],
      "outputs":[],
      "state":[],
      "linkhash":"0x00",
      "transactionid":"0xAB728B0D4A215A520DAA3DB2A618CBD24AB3A3A36293B07FA2EF55CBBD765613"
    },
    "witness":{
      "signatures":[],
      "mmrproofs":[],
      "scripts":[]
    },
    "outputcoindata":[]
  }
}

We have created the shell of a transaction. As you can see there are no inputs or outputs for this transaction yet.

3. Add an input to the transaction

We need a coin to use as an input to the transaction. The coin must be greater than or equal to the value you wish to send.

If you don't have a single coin which is enough to cover the amount you wish to send, you will need to add more than one coin as an input.

To see which coins you have available, use the coins command.

Doing this on node 1, we get the following output:

coins
{
  "command":"coins",
  "status":true,
  "pending":false,
  "response":[{
    "coinid":"0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A",
    "amount":"1000000000",
    "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2",
    "miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ",
    "tokenid":"0x00",
    "token":null,
    "storestate":true,
    "state":[],
    "spent":false,
    "mmrentry":"1",
    "created":"1"
  }]
}

We have one coin, the Genesis coin, worth 1 billion Minima.

The coinid is the unique identifier for the coin and this is what we will use to add this coin as the input to our transaction.

On node 1, add this coin as an input to our simpletxn:

txninput id:simpletxn coinid:0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A

We get the following output:

{
  "command":"txninput",
  "params":{
    "id":"simpletxn",
    "coinid":"0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A"
  },
  "status":true,
  "pending":false,
  "response":{
    "id":"simpletxn",
    "transaction":{
      "inputs":[{
        "coinid":"0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A",
        "amount":"1000000000",
        "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2",
        "miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ",
        "tokenid":"0x00",
        "token":null,
        "storestate":true,
        "state":[],
        "spent":false,
        "mmrentry":"1",
        "created":"1"
      }],
      "outputs":[],
      "state":[],
      "linkhash":"0x00",
      "transactionid":"0xFFF38373DE1EA1FAD6B427F8536FCCA0C3CBF81CB26EDA2F66A48D2ADB84CF86"
    },
    "witness":{
      "signatures":[],
      "mmrproofs":[],
      "scripts":[]
    },
    "outputcoindata":[]
  }
}

As you can see, we have one input now and no outputs.

4. Add outputs to the transaction

Obviously each transaction needs at least 1 output.

Unless you have a coin which is the exact amount you wish to send, a simple transaction would usually take 2 outputs, one to the recipient and one back to the sender with the change (when the value of the input coin is greater than the amount you want to send).

Let's send 10 Minima to node 2.

We need to know a wallet address of node 2, so on node 2 do:

getaddress

You will see the output:

{
  "command":"getaddress",
  "status":true,
  "pending":false,
  "response":{
    "script":"RETURN SIGNEDBY(0x69BF3B984241BB4ADC48517A9F4A94DF25007D7F69E2A376CE939FC45E6A9D0C)",
    "address":"0x1577381B2E4E160BD058F73692A73BBF585B9A68383AD8A55979E7C614A17095",
    "miniaddress":"MxG080YESS1MBWE2Z5T0M7N6Q9AEETVB1DPKQ1Z7BCAAMBPSV3198BGWNB9DRW8",
    "simple":true,
    "default":true,
    "publickey":"0x69BF3B984241BB4ADC48517A9F4A94DF25007D7F69E2A376CE939FC45E6A9D0C",
    "track":true
  }
}

This is one of node 2's default wallet addresses (of which each node has 64).

Each address has a 0x format (address) and an Mx format (miniaddress), either can be used to send coins to.

Each address also has a script and public key.

When we send our 10 Minima to this address MxG080YESS1MBWE2Z5T0M7N6Q9AEETVB1DPKQ1Z7BCAAMBPSV3198BGWNB9DRW8, node 2 will get a new coin, worth 10 Minima, at this address.

The script simply means - for any coins at this address, the coin can only be spent if this script returns true.

4a. Output to recipient

Let's add an output to our transaction, sending 10 Minima to this address.

Back on node 1, do:

txnoutput id:simpletxn amount:10 address:MxG080YESS1MBWE2Z5T0M7N6Q9AEETVB1DPKQ1Z7BCAAMBPSV3198BGWNB9DRW8

Note, we also could have used address:0x1577381B2E4E160BD058F73692A73BBF585B9A68383AD8A55979E7C614A17095.

My command output:

{
  "command":"txnoutput",
  "params":{
    "id":"simpletxn",
    "amount":"10",
    "address":"MxG080YESS1MBWE2Z5T0M7N6Q9AEETVB1DPKQ1Z7BCAAMBPSV3198BGWNB9DRW8"
  },
  "status":true,
  "pending":false,
  "response":{
    "id":"simpletxn",
    "transaction":{
      "inputs":[{
        "coinid":"0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A",
        "amount":"1000000000",
        "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2",
        "miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ",
        "tokenid":"0x00",
        "token":null,
        "storestate":true,
        "state":[],
        "spent":false,
        "mmrentry":"1",
        "created":"1"
      }],
      "outputs":[{
        "coinid":"0x9AA61717A9190419F4C617AF10FC5A014621E860767841118342ABEA9F7F8D4E",
        "amount":"10",
        "address":"0x1577381B2E4E160BD058F73692A73BBF585B9A68383AD8A55979E7C614A17095",
        "miniaddress":"MxG080YESS1MBWE2Z5T0M7N6Q9AEETVB1DPKQ1Z7BCAAMBPSV3198BGWNB9DRW8",
        "tokenid":"0x00",
        "token":null,
        "storestate":true,
        "state":[],
        "spent":false,
        "mmrentry":"0",
        "created":"0"
      }],
      "state":[],
      "linkhash":"0x00",
      "transactionid":"0x210C3C216C12F59C3BDDB9F166F05C25B58178BFC4FB15FCFB464533056EFB57"
    },
    "witness":{
      "signatures":[],
      "mmrproofs":[],
      "scripts":[]
    },
    "outputcoindata":["0x000000209AA61717A9190419F4C617AF10FC5A014621E860767841118342ABEA9F7F8D4E000000201577381B2E4E160BD058F73692A73BBF585B9A68383AD8A55979E7C614A1709500010A00000001000100010000000001000000010000010000"]
  }
}

As you can see, we now have 1 input and 1 output.

You can check the transaction using

txncheck id:simpletxn

Command output:

Minima @ ... : Wrong Number of MMR Proofs Inputs:1 MMRProofs:0 @ 0x00
{
  "command":"txncheck",
  "params":{
    "id":"simpletxn"
  },
  "status":true,
  "pending":false,
  "response":{
    "coins":[{
      "tokenid":"0x00",
      "input":"1000000000",
      "output":"10",
      "difference":"999999990"
    }],
    "tokens":1,
    "inputs":1,
    "outputs":1,
    "burn":"999999990",
    "validamounts":true,
    "signatures":0,
    "valid":{
      "basic":false,
      "signatures":true,
      "mmrproofs":true,
      "scripts":true
    }
  }
}

You will notice the burn amount - 999999990!

The burn is calculated as the difference between the inputs and outputs, so if we don't specify what to do with the remaining 999999990 Minima from the input coin, it will be burned!

4b. Change Output

In this tutorial we won't include a burn (we will assume there is plenty of block space available), so we need to define a second output to return the 999999990 Minima to the sender (node 1).

We can either send it back to the same address that the input coin came from on node 1 i.e. 0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2 or send it back to a different wallet address (which you may want to do for increased privacy).

To find a different wallet address, you can do getaddress on node 1.

For this example, I will send the change back to the same address. The miniaddress (Mx format) would also work.

Add the change output on node 1:

txnoutput id:simpletxn amount:999999990 address:0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2

My command output:

{
  "command":"txnoutput",
  "params":{
    "id":"simpletxn",
    "amount":"999999990",
    "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2"
  },
  "status":true,
  "pending":false,
  "response":{
    "id":"simpletxn",
    "transaction":{
      "inputs":[{
        "coinid":"0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A",
        "amount":"1000000000",
        "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2",
        "miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ",
        "tokenid":"0x00",
        "token":null,
        "storestate":true,
        "state":[],
        "spent":false,
        "mmrentry":"1",
        "created":"1"
      }],
      "outputs":[{
        "coinid":"0x9AA61717A9190419F4C617AF10FC5A014621E860767841118342ABEA9F7F8D4E",
        "amount":"10",
        "address":"0x1577381B2E4E160BD058F73692A73BBF585B9A68383AD8A55979E7C614A17095",
        "miniaddress":"MxG080YESS1MBWE2Z5T0M7N6Q9AEETVB1DPKQ1Z7BCAAMBPSV3198BGWNB9DRW8",
        "tokenid":"0x00",
        "token":null,
        "storestate":true,
        "state":[],
        "spent":false,
        "mmrentry":"0",
        "created":"0"
      },
      {
        "coinid":"0xF25DFF89E78E12926C83E91C64279380BF2C34C4EE5971F015A43614214A6FF8",
        "amount":"999999990",
        "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2",
        "miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ",
        "tokenid":"0x00",
        "token":null,
        "storestate":true,
        "state":[],
        "spent":false,
        "mmrentry":"0",
        "created":"0"
      }],
      "state":[],
      "linkhash":"0x00",
      "transactionid":"0x43D318ACFD77B898DEB7C8F7FEACA3A46BEED0FF35A07B99125238358FEF8B47"
    },
    "witness":{
      "signatures":[],
      "mmrproofs":[],
      "scripts":[]
    },
    "outputcoindata":["0x000000209AA61717A9190419F4C617AF10FC5A014621E860767841118342ABEA9F7F8D4E000000201577381B2E4E160BD058F73692A73BBF585B9A68383AD8A55979E7C614A1709500010A00000001000100010000000001000000010000010000",
    "0x00000020F25DFF89E78E12926C83E91C64279380BF2C34C4EE5971F015A43614214A6FF8000000206B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC200043B9AC9F600000001000100010000000001000000010000010000"]
  }
}

Now we have 1 input (1 billion Minima) and 2 outputs, one to node 2 (10 Minima) and one back to node 1 (999999990 Minima).

If we do txncheck id:simpletxn again, we now have no Burn:

txncheck id:simpletxn
Minima @ ... : Wrong Number of MMR Proofs Inputs:1 MMRProofs:0 @ 0x00
{
  "command":"txncheck",
  "params":{
    "id":"simpletxn"
  },
  "status":true,
  "pending":false,
  "response":{
    "coins":[{
      "tokenid":"0x00",
      "input":"1000000000",
      "output":"1000000000",
      "difference":"0"
    }],
    "tokens":1,
    "inputs":1,
    "outputs":2,
    "burn":"0",
    "validamounts":true,
    "signatures":0,
    "valid":{
      "basic":false,
      "signatures":true,
      "mmrproofs":true,
      "scripts":true
    }
  }
}

You will also see after we added the second output that the Witness data is empty:

    "witness":{
      "signatures":[],
      "mmrproofs":[],
      "scripts":[]
    },

The Witness holds the signatures, coin proofs and scripts for a transaction - proving a transaction's validity.

Let's complete the Witness data.

5. Sign the transaction

Since this is a simple transaction (no custom scripts) we can sign the transaction using

txnsign id:simpletxn publickey:auto

Command output:

{
  "command":"txnsign",
  "params":{
    "id":"simpletxn",
    "publickey":"auto"
  },
  "status":true,
  "pending":false,
  "response":{
    "keys":["0x188A3462BDF4E4238C7097337B6F897ECF806655884FE00D3CFBEEF0C47C6AFD"]
  }
}

The key shown here is the public key used to sign the transaction.

Earlier, I mentioned that each address also has a script and public key.

Let's check the script associated with our input coin address using:

scripts address:0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2

Command output:

{
  "command":"scripts",
  "params":{
    "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2"
  },
  "status":true,
  "pending":false,
  "response":{
    "script":"RETURN SIGNEDBY(0x188A3462BDF4E4238C7097337B6F897ECF806655884FE00D3CFBEEF0C47C6AFD)",
    "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2",
    "miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ",
    "simple":true,
    "default":true,
    "publickey":"0x188A3462BDF4E4238C7097337B6F897ECF806655884FE00D3CFBEEF0C47C6AFD",
    "track":true
  }
}

You can see the publickey here matches what our txnsign command returned.

This tells us that when sending a coin which has this address, the script

RETURN SIGNEDBY(0x188A3462BDF4E4238C7097337B6F897ECF806655884FE00D3CFBEEF0C47C6AFD)

must return TRUE.

This script reads:

If this transaction is SIGNEDBY the public key 0x188A3462BDF4E4238C7097337B6F897ECF806655884FE00D3CFBEEF0C47C6AFD, then return TRUE. Otherwise, return FALSE.

If you do txncheck id:simpletxn again, you will see there is now 1 signature.

If you do txnlist id:simpletxn, you will see a signature is now populated in the Witness section.

However the mmrproofs and scripts are still empty.

Command output from txnlist id:simpletxn:

...
      "mmrproofs":[],
      "scripts":[]
...

Let's add these now.

6. Add the Coin proofs and Scripts

Again, as this is a simple transaction, we can easily add the MMR proof for the input coin and the script using:

txnbasics id:simpletxn

The command output will show you the full transaction and complete Witness, including the mmrproofs and scripts:

...
      "mmrproofs":[{
        "coin":{
          "coinid":"0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A",
          "amount":"1000000000",
          "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2",
          "miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ",
          "tokenid":"0x00",
          "token":null,
          "storestate":true,
          "state":[],
          "spent":false,
          "mmrentry":"1",
          "created":"1"
        },
        "proof":{
          "blocktime":"235",
          "proof":[{
            "left":true,
            "data":{
              "data":"0xA53AD6A229F11DAD05FD0D9164F8EEE96501FA67ED9FEF7087EEA5C43E293357",
              "value":"0"
            }
          }],
          "prooflength":1
        }
      }],
      "scripts":[{
        "script":"RETURN SIGNEDBY(0x188A3462BDF4E4238C7097337B6F897ECF806655884FE00D3CFBEEF0C47C6AFD)",
        "address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2",
        "proof":{
          "blocktime":"0",
          "proof":[],
          "prooflength":0
        }
      }]
    },
    "outputcoindata":["0x000000209AA61717A9190419F4C617AF10FC5A014621E860767841118342ABEA9F7F8D4E000000201577381B2E4E160BD058F73692A73BBF585B9A68383AD8A55979E7C614A1709500010A00000001000100010000000001000000010000010000",
    "0x00000020F25DFF89E78E12926C83E91C64279380BF2C34C4EE5971F015A43614214A6FF8000000206B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC200043B9AC9F600000001000100010000000001000000010000010000"]
  }
}

By adding the coin's MMR proof, when all other nodes in the network receive this transaction, they will be able to verify that our input coin is valid and unspent (i.e. We are not attempting a double spend!)

By adding the script, they will be able to execute the script and verify that it returns TRUE - since we have signed the transaction with the right public key.

Now when you do txncheck id:simpletxn, you won't get the Wrong number of MMR Proofs message and you will see everything is now valid!

...
    "valid":{
      "basic":true,
      "signatures":true,
      "mmrproofs":true,
      "scripts":true
...

7. Post the transaction

We are ready to post the transaction!

All the hard work is done, now we just need to post the transaction - this will propagate it to the entire Minima network who will validate it and then add it to a block!

Still on node 1:

txnpost id:simpletxn

Command output (node 1):

ASYNC Transaction Mined : 0x00004D96A2FFDC5BFC00868627B6A9085ECDE489A83B5CD9A6B76A5FA58DFB3F
You found a block! 530 0x00004D96A2FFDC5BFC00868627B6A9085ECDE489A83B5CD9A6B76A5FA58DFB3F
NEW Spent Coin : {"coinid":"0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A","amount":"1000000000","address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2","miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ","tokenid":"0x00","token":null,"storestate":true,"state":[],"spent":true,"mmrentry":"1","created":"1"}
NEW Unspent Coin : {"coinid":"0xF25DFF89E78E12926C83E91C64279380BF2C34C4EE5971F015A43614214A6FF8","amount":"999999990","address":"0x6B8E37A911B21E380872C14E09FB1F25B1473C8D869B20ACCC269A71DA3A0CC2","miniaddress":"MxG083BHZRQW4DW3ZS0GSM19Z4VM7P5M53JP3C6JCGAPJ16J9ZTKEGCZA4GJAEZ","tokenid":"0x00","token":null,"storestate":true,"state":[],"spent":false,"mmrentry":"3","created":"530"}

On node 2, we can see it has received the Minima:

NEW Unspent Coin : {"coinid":"0x9AA61717A9190419F4C617AF10FC5A014621E860767841118342ABEA9F7F8D4E","amount":"10","address":"0x1577381B2E4E160BD058F73692A73BBF585B9A68383AD8A55979E7C614A17095","miniaddress":"MxG080YESS1MBWE2Z5T0M7N6Q9AEETVB1DPKQ1Z7BCAAMBPSV3198BGWNB9DRW8","tokenid":"0x00","token":null,"storestate":true,"state":[],"spent":false,"mmrentry":"2","created":"530"}

So you can see the process:

1. node 1 created a txpow unit containing the transaction
2. node 1 mined the txpow unit
3. the txpow unit became a block*
4. node 1 spent the 1 billion coin and received a new coin of 999999990
5. node 2 received a new coin of 10

* It is important to note here that step 3 is not a given and in the main network, the block would most likely be found by a different node.

Well done, you just manually constructed a transaction and sent it!

##n Notes

Alternative methods in this tutorial could have been:

1. Instead of using txnbasics id:simpletxn, you could add the MMR proofs and script at the same time as adding the coin as an input with

txninput id:simpletxn coinid:0x9ADD6E64E7D4DE63F4472C730ECEDDA8BC37C2F1A906E126F81C584EF172CF3A scriptmmr:true

2. Instead of using txnbasics id:simpletxn, you could do it in one step with:

txnpost id:simpletxn auto:true

3. If you had more than one coin on node 1, you could add a burn at the txnpost step with:

txnpost id:simpletxn burn:1