create-coin-commitment-multiflag.zk

open Extended_lib;

//mh0 is a Merkel tree root - only public input
let main = fun ( mh0 : field, nf : field, cm_new : field, ()) => {

// (1: validity & 2: ownership)
// I (1) know a route through the merkel tree {M0, M1, M2, M3} leading to a commitment we call t
// ie, hashed with its Merkel sibling M3, then all hashed with Merkel parent M2, then all hashed with Merkel grandparent M1
// gives Merkel root mh0

// Further I (2) know a secret r, a value v and flag which concatenated and hashed give t.

// I know r, flag s.t. HS of {r,v,flag} = some t, s.t.
// t= HM (M0,(M1,(M2,(M3, t))))

// (3: non-inflation)
// TODO: My output value vo is (lt)equal to the value v of the original coin
// v=1

// (4: Flag-carrying)
// TODO: My output commitment does not add extra 'bits' to the flag
// TODO: ie, flag*discarded_flags = flag
// My output commitment has the same flag to the flag of the previous commitment

// (5: nullifiability)
// The nullifier n refers to that commitment t and is signed.
// ie n = hash (r,t)

//NB: In variable names, xxx_bool is generally used to refer to the list(boolean) version of a value. _Not_ bool/ list(bool) !


let params = load_pedersen_params("./constants/bn128-params");

let hash_bits = fun (pre_image : list(boolean)) => {
  Pedersen.digest_bits(params, pre_image);
};

let hash_field = fun (pre_image : field) => {
  Pedersen.digest_bits(params, Field.to_bits(pre_image));
};

let order_nodes = fun (a: field, b_tuple: (field, boolean)) => {
  let (b, lr_bit_b) = b_tuple;
  select(lr_bit_b, ~then_=(a,b), ~else_=(b,a));

  // result
  // .append (dir*a, not dir*b, not dir * a, dir * b)
  // .filter (nonzero)
  // .map (field -> list(bool))
  // result[0]::result[1];
};

let hash_merkle_nodes = fun (ordered_nodes_tuple : (field, field)) => {
  let node1_bool = Field.to_bits( fst(ordered_nodes_tuple) );
  let node2_bool = Field.to_bits( snd(ordered_nodes_tuple) );

  hash_bits ( node1_bool @ node2_bool ) ;
};

let hash_commitment = fun (secret : field, val1 : field, val2 : field) =>  {
  let secret_bool = Field.to_bits(secret);
  let val1_bool = Field.to_bits(val1);
  let val2_bool = Field.to_bits(val2);
  let hashable = secret_bool@val1_bool@val2_bool ;
  let hashable = secret_bool ;

  //TODO: check bit length of 3way concat (defaults are OK? )
  hash_bits(hashable);
};

let hash_nullifier_commitment = fun (secret : field, n : field) =>  {
  let secret_bool = Field.to_bits(secret);
  let n_bool = Field.to_bits(n);
  let hashable = secret_bool@n_bool ;

  hash_bits (secret_bool@n_bool);
};


// TODO: pass private inputs to Prover
  let (r, v, flag, tree_threeple, r', flag', v', discarded_flags) =
    Prover {
      let [r, v, flag, l1_sib_string, l2_sib_string, l3_sib_string, r', v', flag' ] = read_lines ("transfer_secrets") ;
      //let [r, v, flag, l1_sib_string, l2_sib_string, l3_sib_string, r', v', flag' ] = [998, 1, 0, "4567,0", "7385,1", "2372,0", 999, 1, 0];

      let sep = String.get (",",0i);
      let [l1_hash, l1_dir] = String.split_on_char(sep, l1_sib_string);
      let l1_sibling = (Field.of_string(l1_hash), Stdlib.bool_of_string(l1_dir)) ;
      let [l2_hash, l2_dir] =  String.split_on_char(sep, l2_sib_string);
      let l2_sibling = (Field.of_string(l2_hash), Stdlib.bool_of_string(l2_dir)) ;
      let [l3_hash, l3_dir] =  String.split_on_char(sep, l3_sib_string);
      let l3_sibling = (Field.of_string(l3_hash), Stdlib.bool_of_string(l3_dir)) ;

      let r = Field.of_string(r);
      let v = Field.of_string(v);
      let flag = Field.of_string(flag);

      let r' = Field.of_string(r');
      let v' = Field.of_string(v');
      let flag' = Field.of_string(flag');

      //  Get the following:
      //  v : field, flag : field, l1_sibling : (field, boolean), l2_sibling : (field, boolean), l3_sibling : (field, boolean)
      // r,flag,r',flag', v ,v'


//   let level2_parent = hash_merkle_nodes (order_nodes (fst(l3_sibling), fst(l3_sibling)));
//  Field.print (level2_parent);
      (r, v, flag, (l1_sibling, l2_sibling, l3_sibling), r', flag', v') ;
    };

  let t = hash_commitment (r, v, flag);
  let t' = hash_commitment (r',v',flag');

  let (l1_sibling, l2_sibling, l3_sibling) = tree_threeple;

  let t = hash_commitment (r, v, flag);

  let level2_parent = hash_merkle_nodes(order_nodes(t, l3_sibling));
  let level1_parent = hash_merkle_nodes(order_nodes(level2_parent, l2_sibling));
  let calculated_root = hash_merkle_nodes(order_nodes(level1_parent, l1_sibling));

  // nullifier will require commitment to be hashed with secret a second time in order to sign that it refers to this commitment
  // and not another maliciously signed with the same secret but different values
  let n = hash_nullifier_commitment (r, t);

  assert_r1(calculated_root, 1, mh0);
  assert_r1(v, 1, v');
  assert_r1(flag', discarded_flags, flag);
  assert_r1(n, 1, nf);
  assert_r1(t',1,cm_new);
};