Add Circom Pad impl

circuits/keccak256.circom

@@ -0,0 +1,46 @@
+pragma circom 2.0.0;
+
+include "./utils.circom";
+
+template Pad(nBits) {
+    signal input in[nBits];
+    var blockSize=136*8;
+    signal output out[blockSize];
+    signal out2[blockSize];
+    var i;
+
+    for (i=0; i<nBits; i++) {
+        out2[i] <== in[i];
+    }
+    var domain = 0x01;
+    for (i=0; i<8; i++) {
+        out2[nBits+i] <== (domain >> i) & 1;
+    }
+    for (i=nBits+8; i<blockSize; i++) {
+        out2[i] <== 0;
+    }
+    component aux = OrArray(8);
+    for (i=0; i<8; i++) {
+        aux.a[i] <== out2[blockSize-8+i];
+        aux.b[i] <== (0x80 >> i) & 1;
+    }
+    for (i=0; i<8; i++) {
+        out[blockSize-8+i] <== aux.out[i];
+    }
+    for (i=0; i<blockSize-8; i++) {
+        out[i]<==out2[i];
+    }
+}
+
+template Keccak256(nBits) {
+    signal input in[nBits];
+    signal output out[256];
+    var i;
+
+    // pad
+    component pad = Pad(nBits);
+    for (i=0; i<nBits; i++) {
+        pad.in[i] <== in[i];
+    }
+    
+}