You can follow along within the playground for most of the Leo examples - https://play.leo-lang.org/
However as you build out more complex examples and want to deploy, you may want to move to a local environment. We will talk about the tools needed now.
Make sure you have the following software installed on your local machine:
snarkos is the command used to interact with our Aleo node, so it will be used for things like deploying.
snarkos --help
leo is probably the command you will use more often, as it is the command used to interact with our application, or do basic things like create Leo wallets.
leo --help
There is some overlap between tools, so for example, you can create a wallet with both. I’ll generally prefer to use leo when possible. Let’s go through an example of creating a wallet next.
You will need a wallet to deploy your program. You can create a wallet by running the following command:
leo account new
The structure will look something like:
Private Key APrivateKey1zkp57ZaLSVAQjEqfAMZ1QWbi7db3BBCmPkG6Q6fp4qryD6p
View Key AViewKey1mMuL6pMbdQdK3Tqmw1og632Vz2Y9ZSJ5ctF48PhjK64r
Address aleo1yt7t660fx2675gapa8tr5k99cgl7klwsz3gtd9qzcfh0xklwxuqsauh8v6
Be sure to save the Address, View and Private Keys of this wallet, you will need them later.
Record model is similar to that of Bitcoin or the UTXO model compared to an account model.
We will go over some basic vocabulary:
- A record is the smallest data structure for storing state. For example, we can use a record to transfer Aleo credits from one address to another privately.
- We then have a transition. If the records store state, a transition describes a change from one state to another. Through this process, records are consumed and created.
- A transaction, the term most have probably heard, is a collection of transitions that will be published on chain.
- Finally, a block is a collection of transactions allowing for a record of all state changes over time.
You can see this grouping by looking first at a block - https://explorer.hamp.app/block?h=604344
block —> transactions —> transitions —> records
A record will look like:
record1qyqsqy4m2af2k4ncfdz9epcn0rr284z2tdqt67dcpya5cdk84w6yv7q9qyxx66trwfhkxun9v35hguerqqpqzq9wtmyxdukwnwxvqjt9x8pz8gta40g5v8lfkfgpl8k5tlgzg0elqrwt7earvar8zlza6twwzpzacymsy2ms083k0plr0nsc4slu9xwq2yzgrhj
it can be decrypted with your viewkey if it belongs to you.
{
owner: aleo1ej97m92u995kpzn8m0zms65uwasq8w95r6pnepdpnh89c7qug5pqyyykr9.private,
microcredits: 93300000000u64.private,
_nonce: 2537482171121567559953927872334058167419291196003242761090252325051232141276group.public
}
This contains an owner and microcredits, which is the smallest division of an Aleo credit.
https://developer.aleo.org/concepts/transaction_fees/#aleo-credits-denomination-table
The _nonce is just a unique identifier for this record, so the number has no significant meaning.
Run the following command to initialize a Leo project.
leo new hello
Let's take a look at the structure of the project.
Code is written in main.leo.
program hello.aleo {
transition main(public a: u32, b: u32) -> u32 {
let c: u32 = a + b;
return c;
}
}
This describes a program with a Program ID called hello. Then, we have a transition. parameters of type u32 (integer) and a return of u32. This just adds up the values in C and returns C.
To see this execute:
leo run main 10u32 5u32
this should give 15u32
To quickly see zk proofs in action, while kinda silly, this will prove that B is an even number.
program hello.aleo {
transition main(a: u32, b: u32) -> u32 {
assert_eq(b.rem(2u32), 0u32);
let c: u32 = a + b;
return c;
}
}
leo execute main 3u32 5u32
When people say that the inputs remain private, it is specifically referring the arguments to this transition function. So the value 5 is not exposed.
This is a basic example, but illustrates how a ZKP will work.