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Create a Cairo Proof

After transpiling the model to Cairo using Giza CLI, the next step is to create a proof. This proof is a cryptographic evidence that the computation (inference) was done correctly without revealing any information about the data or the computation itself.


We need to install the following tools:

Embed the model into a Starknet Contract

First, we need to compile the Cairo contract to a Starknet Contract, more information about starknet contracts here. For now we don't need to dive deep into how these contracts work, as currently we need to make it a contract due a temporary limitation in the prover, once this is solved we should be able to generate the proof without the need of a contract.
Add the starknet as a dependency in the Scarb.toml file:
starknet = "2.0.2"
orion = { git = "" }
# ...
Then declare our program as a contract:
// inference.cairo
// Create a module and declare it as a contract
mod OrionRunner {
// Kepp your imports as declared previously
// use ...
// Declare the contract storage, in this case is a dummy storage as we won't use it
struct Storage {
id: u8,
// Declare the main function as an external function and add `self: @ContractState` as the first argument
fn main(self: @ContractState){
// The models code goes here
// Remember to close the module bracket!

Compile the contract

This is done using the scarb build command with the main objective of creating the sierra.json file that will be used to generate the proof. These files will be generated in the target/dev folder.
❯ scarb build
Updating git repository
Updating git repository
Updating git repository
Compiling mnist_pytorch v0.1.0 (/Users/gizabrain/src/giza/giza-cli/examples/mnist/mnist_cairo/Scarb.toml)
Finished release target(s) in 7 seconds
Now this will create two files, but we are only interested in one of them, the {{project name}}_OrionRunner.sierra.json file.

Convert the sierra.json file to casm.json

For this step we need the starknet-sierra-compile tool, this tool will convert the sierra.json file to a casm.json. If you don't already have it, to get it you need to get it from the Cairo repository and build it:
git clone [email protected]:starkware-libs/cairo.git
cd cairo
cargo build
Then the binary will be placed at target/debug/starknet-sierra-compile. Now we can use it to convert the file:
starknet-sierra-compile -- target/dev/{{project_name}}_OrionRunner.sierra.json output.casm.json

Generate the proof

Finally, we can generate the proof using the giza prove command:
❯ giza prove --size M output.casm.json
[giza][2023-10-26 13:29:22.337] Proving job created with name 'proof-job-20231026-73fb1007' and id -> 1 ✅
# This log live updates with the job elapsed time
[giza][2023-10-26 13:32:44.431] Job status is 'PROCESSING', elapsed 103.0s
# Once finished it will update to indicate that the job finished
[giza][2023-10-26 13:37:06.634] Proving job is successful ✅
[giza][2023-10-26 13:37:06.748] Proof metrics:
"cairovm_execution_time": 4.973674,
"proving_time": 316.3519
[giza][2023-10-26 13:37:07.471] Proof saved at: zk.proof
And now we have our proof!
Note: The verify command is coming soon!