A Custom Token in Leo

Source Code

Summary

A transparent & shielded custom token in Leo.

How to Run

Follow the Leo Installation Instructions.

This token program can be run using the following bash script. Locally, it will execute Leo program functions to mint and transfer tokens publicly and privately.

cd leo/examples/token
./run.sh

The .env file contains a private key and network type. This is the account that will be used to sign transactions and is checked for record ownership. When executing programs as different parties, be sure to set the private_key field in .env to the appropriate value. You can check out how we have set things up in ./run.sh for a full example of how to run the program as different parties.

Walkthrough

• Step 0: Public Mint
• Step 1: Private Mint
• Step 2: Public Transfer
• Step 3: Private Transfer
• Step 4: Public to Private Transfer
• Step 5: Private to Public Transfer

We will be conducting a transfer between two parties.

The private key and address of Alice.
private_key: APrivateKey1zkp1w8PTxrRgGfAtfKUSq43iQyVbdQHfhGbiNPEg2LVSEXR
address: aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q

The private key and address of Bob.
private_key: APrivateKey1zkpFo72g7N9iFt3JzzeG8CqsS5doAiXyFvNCgk2oHvjRCzF
address: aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z

Public Mint

Act as Alice. Put her private key in .env. Publicly mint 100 tokens.

echo "
NETWORK=testnet
PRIVATE_KEY=APrivateKey1zkp1w8PTxrRgGfAtfKUSq43iQyVbdQHfhGbiNPEg2LVSEXR
" > .env

leo run mint_public aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q 100u64

Output

 • {
  program_id: token.aleo,
  function_name: mint_public,
  arguments: [
    aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q,
    100u64
  ]
}

You can see the output of mint_public, which takes the arguments Alice's address and the amount of tokens to mint publicly. This information is shown on-chain and can be queried on a network.

Private Mint

Now, privately mint 100 tokens for Bob. Put Bob's private key in .env. Run the private mint function.

echo "
NETWORK=testnet
PRIVATE_KEY=APrivateKey1zkpFo72g7N9iFt3JzzeG8CqsS5doAiXyFvNCgk2oHvjRCzF
" > .env

leo run mint_private aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z 100u64

Output

 • {
  owner: aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z.private,
  amount: 100u64.private,
  _nonce: 4719474923967087502681846187174640869781874305919806595754990568074403149805group.public
}

The output is a private record.

Public Transfer

Publicly transfer 10 tokens from Alice to Bob. Put Alice's private key in .env. Call the public transfer function.

echo "
NETWORK=testnet
PRIVATE_KEY=APrivateKey1zkp1w8PTxrRgGfAtfKUSq43iQyVbdQHfhGbiNPEg2LVSEXR
" > .env

leo run transfer_public aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z 10u64

Output

 • {
  program_id: token.aleo,
  function_name: transfer_public,
  arguments: [
    aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q,
    aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z,
    10u64
  ]
}

Again, we see the arguments used for the final block of transfer_public - Alice's address, Bob's address, and the amount to transfer. The public mapping will be queryable on-chain.

Private Transfer

Privately transfer 20 tokens from Bob to Alice. Put Bob's private key in .env. Call the private transfer function.

echo "
NETWORK=testnet
PRIVATE_KEY=APrivateKey1zkpFo72g7N9iFt3JzzeG8CqsS5doAiXyFvNCgk2oHvjRCzF
" > .env

leo run transfer_private "{
    owner: aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z.private,
    amount: 100u64.private,
    _nonce: 6586771265379155927089644749305420610382723873232320906747954786091923851913group.public
}" aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q 20u64

Output

 • {
  owner: aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z.private,
  amount: 80u64.private,
  _nonce: 7402942372117092417133095075129616994719981532373540395650657400913787695842group.public
}
 • {
  owner: aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q.private,
  amount: 20u64.private,
  _nonce: 2444690320093734417295179000152972034731859256625211879727315719617371330248group.public
}

transfer_private outputs two records. Bob owns the first record, which contains the balance after the 20-token transfer. Alice owns the second record, which contains the 20 transferred tokens.

Public to Private Transfer

Convert 30 of Alice's public tokens into 30 private tokens for Bob. Put Alice's private key in .env.

echo "
NETWORK=testnet
PRIVATE_KEY=APrivateKey1zkp1w8PTxrRgGfAtfKUSq43iQyVbdQHfhGbiNPEg2LVSEXR
" > .env

leo run transfer_public_to_private aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z 30u64

Output

 • {
  owner: aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z.private,
  amount: 30u64.private,
  _nonce: 2372167793514585424629802909684994302673167688345985265672131682042636755887group.public
}
 • {
  program_id: token.aleo,
  function_name: transfer_public_to_private,
  arguments: [
    aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q,
    30u64
  ]
}

Calling transfer_public_to_private outputs finalization data, which indicates code to be run on-chain, along with its associated inputs.

Private to Public Transfer

Convert 40 of Bob's private tokens into 40 public tokens for Alice. Put Bob's private key in .env.

echo "
NETWORK=testnet
PRIVATE_KEY=APrivateKey1zkpFo72g7N9iFt3JzzeG8CqsS5doAiXyFvNCgk2oHvjRCzF
" > .env

leo run transfer_private_to_public "{
    owner: aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z.private,
    amount: 80u64.private,
    _nonce: 1852830456042139988098466781381363679605019151318121788109768539956661608520group.public
}" aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q 40u64

Output

 • {
  owner: aleo17vy26rpdhqx4598y5gp7nvaa9rk7tnvl6ufhvvf4calsrrqdaqyshdsf5z.private,
  amount: 40u64.private,
  _nonce: 2233440107615267344685761424001099994586652279869516904008515754794838882197group.public
}
 • {
  program_id: token.aleo,
  function_name: transfer_private_to_public,
  arguments: [
    aleo13ssze66adjjkt795z9u5wpq8h6kn0y2657726h4h3e3wfnez4vqsm3008q,
    40u64
  ]
}

transfer_private_to_public consumes Bob's private record with 110 tokens. It outputs Bob's private record with 70 tokens and the finalization data that runs on-chain.