feat: nonzero DataHasher (#45)

* Delete notes.md * feat: updated `DataHasher` * feat: tested `DataHasher` * test: one more example * Update package.json --------- Co-authored-by: Sambhav Dusad <[email protected]>
pluto · Nov 14, 2024 · 3fdfd5c · 3fdfd5c
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Showing 6 changed files with 47 additions and 18 deletions.
diff --git a/circuits/http/nivc/notes.md b/circuits/http/nivc/notes.md
diff --git a/circuits/test/common/poseidon.ts b/circuits/test/common/poseidon.ts
@@ -88,8 +88,12 @@ export function DataHasher(input: number[]): bigint {
             packedInput += BigInt(input[16 * i + j]) * BigInt(2 ** (8 * j));
         }
 
-        // Compute next hash using previous hash and packed input
-        hashes.push(PoseidonModular([hashes[i], packedInput]));
+        // Compute next hash using previous hash and packed input, but if packed input is zero, don't hash it.
+        if (packedInput == BigInt(0)) {
+            hashes.push(hashes[i]);
+        } else {
+            hashes.push(PoseidonModular([hashes[i], packedInput]));
+        }
     }
 
     // Return the last hash

diff --git a/circuits/test/full/full.test.ts b/circuits/test/full/full.test.ts
@@ -2,8 +2,6 @@ import { assert } from "chai";
 import { circomkit, WitnessTester, toByte } from "../common";
 import { DataHasher } from "../common/poseidon";
 
-
-
 // HTTP/1.1 200 OK
 // content-type: application/json; charset=utf-8
 // content-encoding: gzip

diff --git a/circuits/test/utils/hash.test.ts b/circuits/test/utils/hash.test.ts
@@ -1,5 +1,6 @@
+import assert from "assert";
 import { circomkit, WitnessTester } from "../common";
-import { PoseidonModular } from "../common/poseidon";
+import { DataHasher, PoseidonModular } from "../common/poseidon";
 
 describe("hash", () => {
     describe("PoseidonModular_16", () => {
@@ -83,10 +84,9 @@ describe("hash", () => {
 
         it("witness: in = [0,...x16]", async () => {
             const input = Array(16).fill(0);
-            const hash = PoseidonModular([0, 0]);
             await circuit.expectPass(
                 { in: input },
-                { out: hash }
+                { out: 0 }
             );
         });
 
@@ -128,8 +128,23 @@ describe("hash", () => {
         10, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 125, 13, 10, 32, 32, 32, 32, 32, 32, 32, 93, 13,
         10, 32, 32, 32, 125, 13, 10, 125]
 
+    const http_start_line = [
+        72, 84, 84, 80, 47, 49, 46, 49, 32, 50, 48, 48, 32, 79, 75, 13, 10, 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, 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, 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, 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, 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, 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, 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, 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, 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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0,
+    ];
+
     describe("DataHasherHTTP", () => {
         let circuit: WitnessTester<["in"], ["out"]>;
+        let circuit_small: WitnessTester<["in"], ["out"]>;
 
         before(async () => {
             circuit = await circomkit.WitnessTester(`DataHasher`, {
@@ -138,13 +153,28 @@ describe("hash", () => {
                 params: [320],
             });
             console.log("#constraints:", await circuit.getConstraintCount());
+
+            circuit_small = await circomkit.WitnessTester(`DataHasher`, {
+                file: "utils/hash",
+                template: "DataHasher",
+                params: [32],
+            });
+            console.log("#constraints:", await circuit.getConstraintCount());
         });
 
         it("witness: TEST HTTP BYTES", async () => {
-
+            let hash = DataHasher(TEST_HTTP_BYTES);
+            assert.deepEqual(String(hash), "2195365663909569734943279727560535141179588918483111718403427949138562480675");
             await circuit.expectPass({ in: TEST_HTTP_BYTES }, { out: "2195365663909569734943279727560535141179588918483111718403427949138562480675" });
         });
 
+        let hash = DataHasher(http_start_line);
+        it("witness: TEST HTTP START LINE MASK", async () => {
+            await circuit.expectPass({ in: http_start_line }, { out: hash });
+        });
 
+        it("witness: TEST HTTP START LINE MASK TRUNCATED", async () => {
+            await circuit_small.expectPass({ in: http_start_line.slice(0, 32) }, { out: hash });
+        });
     });
-});
+});
diff --git a/circuits/utils/hash.circom b/circuits/utils/hash.circom
@@ -72,16 +72,18 @@ template DataHasher(DATA_BYTES) {
     signal input in[DATA_BYTES];
     signal output out;
 
+    signal not_to_hash[DATA_BYTES \ 16];
+    signal option_hash[DATA_BYTES \ 16];
     signal hashes[DATA_BYTES \ 16 + 1];
     hashes[0] <== 0;
-
     for(var i = 0 ; i < DATA_BYTES \ 16 ; i++) {
         var packedInput = 0;
         for(var j = 0 ; j < 16 ; j++) {
             packedInput += in[16 * i + j] * 2**(8*j);
         }
-        hashes[i+1] <== PoseidonChainer()([hashes[i],packedInput]);
+        not_to_hash[i] <== IsZero()(packedInput);
+        option_hash[i] <== PoseidonChainer()([hashes[i],packedInput]);
+        hashes[i+1]    <== not_to_hash[i] * (hashes[i] - option_hash[i]) + option_hash[i]; // same as: (1 - not_to_hash[i]) * option_hash[i] + not_to_hash[i] * hash[i];
     }
-
     out <== hashes[DATA_BYTES \ 16];
 }
diff --git a/package.json b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "web-prover-circuits",
   "description": "ZK Circuits for WebProofs",
-  "version": "0.5.3",
+  "version": "0.5.4",
   "license": "Apache-2.0",
   "repository": {
     "type": "git",