Generating Proofs

Generating Proofs

The SHARP (Shared Prover) Service allows for the generation of proofs that attest to the validity of Cairo program executions.

Cairo programs that are executed by the SHARP Service need to produce outputs.

Proofs are verified by a Smart Contract on Ethereum.


The following is a Cairo program that checks if the numbers passed-in as inputs are the prime factors of the prime number 15.

# The program produces outputs which require the `output` builtin.
%builtins output

from starkware.cairo.common.serialize import serialize_word

func main{output_ptr : felt*}():

    local prime_1
    local prime_2
    let expected = 15

    # Read the Prime factors from the input and store them in local variables.
        ids.prime_1 = program_input["prime_1"]
        ids.prime_2 = program_input["prime_2"]

    # Compute the potential Prime number.
    let result = prime_1 * prime_2

    # Throw an error if the Prime factors are invalid.
    assert result = expected

    # Output Prime factors and Prime number.

    return ()

An input.json file for the program might look like this:

  "prime_1": 3,
  "prime_2": 5

The program can be compiled and sent off to the SHARP Service with the following command:

cairo-sharp submit --source sharp.cairo --program_input input.json

The output generated includes the Job key which is a unique identifier created and assigned by the SHARP Service as well as the the Fact which is the result of hashing the program hash and the hash of the output.

Submitting to SHARP...
Job sent.
Job key: 73500390-65dc-446d-a29a-9a09348998d4
Fact: 0x0fb87734675291a4cb80db62ca1d66472bfd157a4d24b985bec72e577244a545

The status of the Job can be obtained via the Job key and the following command:

cairo-sharp status 73500390-65dc-446d-a29a-9a09348998d4

Once the status query reports PROCESSED the Fact can be verified (note that the Fact identifier is used, not the Job key):

cairo-sharp is_verified 0x0fb87734675291a4cb80db62ca1d66472bfd157a4d24b985bec72e577244a545 --node_url

The Fact identifier can also be derived programmatically:

from web3 import Web3
def main():
    # Program Hash is the Pedersen Hash of the compiled program.
    # Can be obtained via the [Cairo Playground]( as
    #   it's output when clicking the "Run" button.
    # Note: The Program Hash does not depend on the input provided.
    program_hash = 0x06F8F5FA88CC63195A6CC0063AF3579CD8F11C3725DD8B2B0D76B8127B0A401C
    program_output = [3, 5, 15]
    fact = Web3.solidityKeccak(
        ["uint256", "bytes32"],
        [program_hash, Web3.solidityKeccak(["uint256[]"], [program_output])],
if __name__ == "__main__":

Running this script returns the same Fact identifier like the execution of cairo-sharp submit above:



Fact Registry Contract - Goerli Alpha