add splitSignalsToWords

circuits/circuits/utils/circomlib/utils/bytes.circom

@@ -182,4 +182,44 @@ template ByteMask(maxLength) {
         bit_check[i].in <== mask[i];
         out[i] <== in[i] * mask[i];
     }
+}
+
+/// NOTE: this circuit is unaudited and should not be used in production
+/// @title SplitBytesToWords
+/// @notice split an array of bytes into an array of words
+/// @notice useful for casting a message or modulus before RSA verification
+/// @param l: number of bytes in the input array
+/// @param n: number of bits in a word
+/// @param k: number of words
+/// @input in: array of bytes
+/// @output out: array of words
+template SplitSignalsToWords (t,l,n,k) {
+    assert(n*k >= t*l);
+
+    signal input in[l];
+    signal output out[k];
+    component num2bits[l];
+    for (var i = 0 ; i < l ; i++){
+        num2bits[i] = Num2Bits(t);
+        num2bits[i].in <== in[i];
+    }
+    for (var i = 0 ; i < t ; i ++){
+    }
+    component bits2num[k];
+    for (var i = 0 ; i < k ; i++){
+        bits2num[i] = Bits2Num(n);
+
+        for(var j = 0 ; j < n ; j++){
+            if(i*n + j >= l  * t){
+                bits2num[i].in[j] <==  0;
+            }
+            else{
+                bits2num[i].in[j] <== num2bits[ (( i * n + j) \ t) ].out[ ((i * n + j) % t)];
+            }
+            }
+    }
+    for( var i = 0 ; i< k ; i++){
+    out[i] <== bits2num[i].out;
+    }
+
 }