From d9d6e43143d4eb780346351e12dad90e72831388 Mon Sep 17 00:00:00 2001
From: adriamb <adria@codecontext.io>
Date: Sun, 17 Mar 2019 10:38:36 +0100
Subject: [PATCH] added pvk->pbk circuit

---
 circuits/babyjub.circom           | 27 +++++++++++++++++++++++++++
 test/babyjub.js                   | 29 +++++++++++++++++++++++++++--
 test/circuits/babypbk_test.circom |  3 +++
 3 files changed, 57 insertions(+), 2 deletions(-)
 create mode 100644 test/circuits/babypbk_test.circom

diff --git a/circuits/babyjub.circom b/circuits/babyjub.circom
index a2e6b6b..c6fe41c 100644
--- a/circuits/babyjub.circom
+++ b/circuits/babyjub.circom
@@ -17,6 +17,9 @@
     along with circom. If not, see <https://www.gnu.org/licenses/>.
 */
 
+include "bitify.circom";
+include "escalarmulfix.circom";
+
 template BabyAdd() {
     signal input x1;
     signal input y1;
@@ -77,3 +80,27 @@ template BabyCheck() {
 
     a*x2 + y2 === 1 + d*x2*y2;
 }
+
+// Extracts the public key from private key
+template BabyPbk() {
+    signal private input  in;
+    signal         output Ax;
+    signal         output Ay;
+
+    var BASE8 = [
+        17777552123799933955779906779655732241715742912184938656739573121738514868268,
+        2626589144620713026669568689430873010625803728049924121243784502389097019475
+    ];
+
+    component pvkBits = Num2Bits(253);
+    pvkBits.in <== in;
+
+    component mulFix = EscalarMulFix(253, BASE8);
+
+    var i;
+    for (i=0; i<253; i++) {
+        mulFix.e[i] <== pvkBits.out[i];
+    }
+    Ax  <== mulFix.out[0];
+    Ay  <== mulFix.out[1];
+}
diff --git a/test/babyjub.js b/test/babyjub.js
index abe1b0b..f47db49 100644
--- a/test/babyjub.js
+++ b/test/babyjub.js
@@ -3,10 +3,12 @@ const path = require("path");
 const snarkjs = require("snarkjs");
 const compiler = require("circom");
 
-const assert = chai.assert;
+const createBlakeHash = require("blake-hash");
+const eddsa = require("../src/eddsa.js");
 
-const bigInt = require("big-integer");
+const assert = chai.assert;
 
+const bigInt = require("snarkjs").bigInt;
 
 describe("Baby Jub test", function () {
     let circuitAdd;
@@ -22,6 +24,11 @@ describe("Baby Jub test", function () {
         const cirDefTest = await compiler(path.join(__dirname, "circuits", "babycheck_test.circom"));
         circuitTest = new snarkjs.Circuit(cirDefTest);
         console.log("NConstrains BabyTest: " + circuitTest.nConstraints);
+
+        const cirDefPbk = await compiler(path.join(__dirname, "circuits", "babypbk_test.circom"));
+        circuitPbk = new snarkjs.Circuit(cirDefPbk);
+        console.log("NConstrains BabyPbk: " + circuitPbk.nConstraints);
+
     });
 
     it("Should add point (0,1) and (0,1)", async () => {
@@ -97,4 +104,22 @@ describe("Baby Jub test", function () {
         }
     });
 
+    it("Should extract the public key from the private one", async () => {    
+
+        const rawpvk = Buffer.from("0001020304050607080900010203040506070809000102030405060708090021", "hex");
+        const pvk    = eddsa.pruneBuffer(createBlakeHash("blake512").update(rawpvk).digest().slice(0,32));
+        const S      = bigInt.leBuff2int(pvk).shr(3);
+
+        const A      = eddsa.prv2pub(rawpvk);
+
+        const input = {
+            in : S,
+            Ax : A[0],
+            Ay : A[1]
+        }
+
+        const w = circuitPbk.calculateWitness(input);
+        assert(circuitPbk.checkWitness(w));
+    });
+
 });
diff --git a/test/circuits/babypbk_test.circom b/test/circuits/babypbk_test.circom
new file mode 100644
index 0000000..2583bb9
--- /dev/null
+++ b/test/circuits/babypbk_test.circom
@@ -0,0 +1,3 @@
+include "../../circuits/babyjub.circom";
+
+component main = BabyPbk();
\ No newline at end of file