First iteration sha256

circuits/sha256/ch.circom

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+/* Ch
+
+000 0
+001 1
+010 0
+011 1
+100 0
+101 0
+110 1
+111 1
+
+out = a&b ^ (!a)&c =>
+
+out = a*(b-c) + c
+
+*/
+
+template Ch(n) {
+    signal input a[n];
+    signal input b[n];
+    signal input c[n];
+    signal output out[n];
+
+    for (var k=0; k<n; k++) {
+        out[k] <== a[k] * (b[k]-c[k]) + c[k];
+    }
+}