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zkinterface.rs
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zkinterface.rs
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use flat_absy::flat_variable::FlatVariable;
use ir::{self, Statement};
use proof_system::ProofSystem;
use std::collections::HashMap;
use std::fs::File;
use std::io::{BufReader, Write};
use zkinterface::{
flatbuffers::{FlatBufferBuilder, WIPOffset},
writing::{CircuitOwned, VariablesOwned},
zkinterface_generated::zkinterface::{
BilinearConstraint,
BilinearConstraintArgs,
Message,
R1CSConstraints,
R1CSConstraintsArgs,
Root,
RootArgs,
Variables,
VariablesArgs,
Witness,
WitnessArgs,
},
};
use zokrates_field::field::{Field, FieldPrime};
pub static FIELD_LENGTH: usize = 32;
pub struct ZkInterface {}
impl ZkInterface {
pub fn new() -> ZkInterface {
ZkInterface {}
}
}
impl ProofSystem for ZkInterface {
fn setup(&self, program: ir::Prog<FieldPrime>, pk_path: &str, _vk_path: &str) {
let mut out_file = File::create(pk_path).unwrap();
setup(program, &mut out_file)
}
fn generate_proof(
&self,
program: ir::Prog<FieldPrime>,
witness: ir::Witness<FieldPrime>,
_pk_path: &str,
proof_path: &str,
) -> bool {
let mut out_file = File::create(proof_path).unwrap();
generate_proof(program, witness, &mut out_file)
}
fn export_solidity_verifier(&self, _reader: BufReader<File>) -> String {
"export_solidity_verifier is not implemented".to_string()
}
}
pub fn setup<W: Write>(program: ir::Prog<FieldPrime>, out_file: &mut W) {
// transform to R1CS
let (variables, first_local_id, a, b, c) = r1cs_program(program);
let free_variable_id = variables.len() as u64;
// Write Return message including free_variable_id.
write_circuit(
first_local_id as u64,
free_variable_id,
None,
true,
out_file);
// Write R1CSConstraints message.
write_r1cs(&a, &b, &c, out_file);
}
pub fn generate_proof<W: Write>(
program: ir::Prog<FieldPrime>,
witness: ir::Witness<FieldPrime>,
out_file: &mut W,
) -> bool {
let (
public_inputs_arr,
private_inputs_arr,
) = prepare_generate_proof(program, witness);
let first_local_id = public_inputs_arr.len() as u64;
let free_variable_id = first_local_id + private_inputs_arr.len() as u64;
// Write Return message including output values.
write_circuit(
first_local_id,
free_variable_id,
Some(&public_inputs_arr),
false,
out_file);
// Write assignment to local variables.
write_assignment(
first_local_id as u64,
&private_inputs_arr,
out_file);
true
}
fn write_r1cs<W: Write>(
a: &Vec<Vec<(usize, FieldPrime)>>,
b: &Vec<Vec<(usize, FieldPrime)>>,
c: &Vec<Vec<(usize, FieldPrime)>>,
out_file: &mut W,
) {
let mut builder = FlatBufferBuilder::new();
// create vector of
let mut vector_lc = vec![];
for i in 0..a.len() {
let a_var_val = convert_linear_combination(&mut builder, &a[i]);
let b_var_val = convert_linear_combination(&mut builder, &b[i]);
let c_var_val = convert_linear_combination(&mut builder, &c[i]);
let lc = BilinearConstraint::create(&mut builder, &BilinearConstraintArgs {
linear_combination_a: Some(a_var_val),
linear_combination_b: Some(b_var_val),
linear_combination_c: Some(c_var_val),
});
vector_lc.push(lc);
}
let vector_offset = builder.create_vector(vector_lc.as_slice());
let args = R1CSConstraintsArgs { constraints: Some(vector_offset), info: None };
let r1cs_constraints = R1CSConstraints::create(&mut builder, &args);
let root_args = RootArgs { message_type: Message::R1CSConstraints, message: Some(r1cs_constraints.as_union_value()) };
let root = Root::create(&mut builder, &root_args);
builder.finish_size_prefixed(root, None);
out_file.write_all(builder.finished_data()).unwrap();
}
fn convert_linear_combination<'a>(builder: &mut FlatBufferBuilder<'a>, item: &Vec<(usize, FieldPrime)>) -> (WIPOffset<Variables<'a>>) {
let mut variable_ids: Vec<u64> = Vec::new();
let mut values: Vec<u8> = Vec::new();
for i in 0..item.len() {
variable_ids.push(item[i].0 as u64);
let mut bytes = item[i].1.into_byte_vector();
bytes.resize(FIELD_LENGTH, 0);
values.append(&mut bytes);
}
let variable_ids = Some(builder.create_vector(&variable_ids));
let values = Some(builder.create_vector(&values));
Variables::create(builder, &VariablesArgs {
variable_ids,
values,
info: None,
})
}
fn write_assignment<W: Write>(
first_local_id: u64,
local_values: &[FieldPrime],
out_file: &mut W,
) {
let mut builder = &mut FlatBufferBuilder::new();
let mut ids = vec![];
let mut values = vec![];
for i in 0..local_values.len() {
ids.push(first_local_id + i as u64);
let mut bytes = local_values[i].into_byte_vector();
bytes.resize(FIELD_LENGTH, 0);
values.append(&mut bytes);
}
let ids = builder.create_vector(&ids);
let values = builder.create_vector(&values);
let values = Variables::create(&mut builder, &VariablesArgs {
variable_ids: Some(ids),
values: Some(values),
info: None,
});
let assign = Witness::create(&mut builder, &WitnessArgs {
assigned_variables: Some(values),
});
let message = Root::create(&mut builder, &RootArgs {
message_type: Message::Witness,
message: Some(assign.as_union_value()),
});
builder.finish_size_prefixed(message, None);
out_file.write_all(builder.finished_data()).unwrap();
}
fn write_circuit<W: Write>(
first_local_id: u64,
free_variable_id: u64,
public_inputs: Option<&[FieldPrime]>,
r1cs_generation: bool,
out_file: &mut W,
) {
// Convert element representations.
let values = public_inputs.map(|public_inputs| {
assert_eq!(public_inputs.len() as u64, first_local_id);
let mut values = vec![];
for value in public_inputs {
let mut bytes = value.into_byte_vector();
bytes.resize(FIELD_LENGTH, 0);
values.append(&mut bytes);
}
values
});
let gadget_return = CircuitOwned {
connections: VariablesOwned {
variable_ids: (0..first_local_id).collect(),
values,
},
free_variable_id,
r1cs_generation,
field_maximum: None,
};
gadget_return.write(out_file).unwrap();
}
fn prepare_generate_proof<T: Field>(
program: ir::Prog<T>,
witness: ir::Witness<T>,
) -> (Vec<T>, Vec<T>) {
// recover variable order from the program
let (variables, public_variables_count, _, _, _) = r1cs_program(program);
let witness: Vec<T> = variables.iter().map(|x| witness.0[x].clone()).collect();
// split witness into public and private inputs at offset
let mut public_inputs: Vec<T> = witness.clone();
let private_inputs: Vec<T> = public_inputs.split_off(public_variables_count);
(
public_inputs,
private_inputs,
)
}
fn provide_variable_idx(
variables: &mut HashMap<FlatVariable, usize>,
var: &FlatVariable,
) -> usize {
let index = variables.len();
*variables.entry(*var).or_insert(index)
}
fn r1cs_program<T: Field>(
prog: ir::Prog<T>,
) -> (
Vec<FlatVariable>,
usize,
Vec<Vec<(usize, T)>>,
Vec<Vec<(usize, T)>>,
Vec<Vec<(usize, T)>>,
) {
let mut variables: HashMap<FlatVariable, usize> = HashMap::new();
provide_variable_idx(&mut variables, &FlatVariable::one());
for x in prog
.main
.arguments
.iter()
.enumerate()
.filter(|(index, _)| !prog.private[*index])
{
provide_variable_idx(&mut variables, &x.1);
}
//Only the main function is relevant in this step, since all calls to other functions were resolved during flattening
let main = prog.main;
//~out are added after main's arguments as we want variables (columns)
//in the r1cs to be aligned like "public inputs | private inputs"
let main_return_count = main.returns.len();
for i in 0..main_return_count {
provide_variable_idx(&mut variables, &FlatVariable::public(i));
}
// position where private part of witness starts
let private_inputs_offset = variables.len();
// first pass through statements to populate `variables`
for (quad, lin) in main.statements.iter().filter_map(|s| match s {
Statement::Constraint(quad, lin) => Some((quad, lin)),
Statement::Directive(..) => None,
}) {
for (k, _) in &quad.left.0 {
provide_variable_idx(&mut variables, &k);
}
for (k, _) in &quad.right.0 {
provide_variable_idx(&mut variables, &k);
}
for (k, _) in &lin.0 {
provide_variable_idx(&mut variables, &k);
}
}
let mut a = vec![];
let mut b = vec![];
let mut c = vec![];
// second pass to convert program to raw sparse vectors
for (quad, lin) in main.statements.into_iter().filter_map(|s| match s {
Statement::Constraint(quad, lin) => Some((quad, lin)),
Statement::Directive(..) => None,
}) {
a.push(
quad.left
.0
.into_iter()
.map(|(k, v)| (variables.get(&k).unwrap().clone(), v))
.collect(),
);
b.push(
quad.right
.0
.into_iter()
.map(|(k, v)| (variables.get(&k).unwrap().clone(), v))
.collect(),
);
c.push(
lin.0
.into_iter()
.map(|(k, v)| (variables.get(&k).unwrap().clone(), v))
.collect(),
);
}
// Convert map back into list ordered by index
let mut variables_list = vec![FlatVariable::new(0); variables.len()];
for (k, v) in variables.drain() {
assert_eq!(variables_list[v], FlatVariable::new(0));
std::mem::replace(&mut variables_list[v], k);
}
(variables_list, private_inputs_offset, a, b, c)
}
#[cfg(test)]
mod tests {
use crate::compile::compile;
use crate::imports::Error;
use super::{FIELD_LENGTH, generate_proof, setup};
use zkinterface::reading::{Constraint, Messages, Term, Variable};
use zokrates_field::field::{Field, FieldPrime};
fn encode(x: u8) -> [u8; 32] {
return [x, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
}
#[test]
fn test_zkinterface() {
assert!(FieldPrime::get_required_bits() < FIELD_LENGTH * 8);
let empty = &[] as &[u8];
let one = &encode(1);
let minus_one = &[0, 0, 0, 240, 147, 245, 225, 67, 145, 112, 185, 121, 72, 232, 51, 40, 93, 88, 129, 129, 182, 69, 80, 184, 41, 160, 49, 225, 114, 78, 100, 48 as u8];
let code = "
def main(field x, private field y) -> (field):
field xx = x * x
field yy = y * y
return xx + yy - 1
";
let program = compile::<FieldPrime, &[u8], &[u8], Error>(
&mut code.as_bytes(), None, None).unwrap();
// Check the constraint system.
{
let mut buf = Vec::<u8>::new();
setup(program.clone(), &mut buf);
let mut messages = Messages::new(0);
messages.push_message(buf).unwrap();
assert_eq!(messages.into_iter().count(), 2);
let circuit = messages.last_circuit().unwrap();
assert_eq!(circuit.free_variable_id(), 6);
let pub_vars = messages.connection_variables().unwrap();
assert_eq!(pub_vars, vec![
Variable { id: 0, value: empty }, // one
Variable { id: 1, value: empty }, // x
Variable { id: 2, value: empty }, // return
]);
let pri_vars = messages.private_variables().unwrap();
assert_eq!(pri_vars, vec![
Variable { id: 3, value: empty }, // xx
Variable { id: 4, value: empty }, // y
Variable { id: 5, value: empty }, // yy
]);
let cs: Vec<_> = messages.iter_constraints().collect();
assert_eq!(cs, vec![
Constraint {
a: vec![Term { id: 1, value: one }], // x
b: vec![Term { id: 1, value: one }], // x
c: vec![Term { id: 3, value: one }], // xx
},
Constraint {
a: vec![Term { id: 4, value: one }], // y
b: vec![Term { id: 4, value: one }], // y
c: vec![Term { id: 5, value: one }], // yy
},
Constraint {
a: vec![Term { id: 0, value: one }], // 1
b: vec![Term { id: 3, value: one }, Term { id: 5, value: one }, Term { id: 0, value: minus_one }], // xx + yy - 1
c: vec![Term { id: 2, value: one }], // return
},
]);
}
let witness = program
.clone()
.execute::<FieldPrime>(&vec![FieldPrime::from(3), FieldPrime::from(4)])
.unwrap();
// Check the witness.
{
let mut buf = Vec::<u8>::new();
generate_proof(program, witness, &mut buf);
let mut messages = Messages::new(0);
messages.push_message(buf).unwrap();
assert_eq!(messages.into_iter().count(), 2);
let circuit = messages.last_circuit().unwrap();
assert_eq!(circuit.free_variable_id(), 6);
let pub_vars = messages.connection_variables().unwrap();
assert_eq!(pub_vars, vec![
Variable { id: 0, value: &encode(1) }, // one
Variable { id: 1, value: &encode(3) }, // x
Variable { id: 2, value: &encode(5 * 5 - 1) }, // return
]);
let pri_vars = messages.private_variables().unwrap();
assert_eq!(pri_vars, vec![
Variable { id: 3, value: &encode(3 * 3) }, // xx
Variable { id: 4, value: &encode(4) }, // y
Variable { id: 5, value: &encode(4 * 4) }, // yy
]);
}
}
}