add bitwise funcs for CEK encrypt/decrypt

bitwise.go

@@ -0,0 +1,32 @@
+package main
+
+// bitwiseComplimentOf returns the bitwise compliment of data
+func bitwiseComplimentOf(data []byte) []byte {
+	compliment := []byte{}
+
+	for i := range data {
+		compliment = append(compliment, ^data[i])
+	}
+
+	return compliment
+}
+
+// isBitwiseCompliment returns true if data1 and data2 are bitwise compliments,
+// otherwise it returns false
+func isBitwiseCompliment(data1, data2 []byte) bool {
+	// if not same length, definitely not compliments
+	if len(data1) != len(data2) {
+		return false
+	}
+
+	// check each byte
+	for i := range data1 {
+		// if any byte is NOT the bitwise compliment of the matching byte in other data
+		// set, then the full set is not bitwise compliment and false
+		if data1[i] != ^data2[i] {
+			return false
+		}
+	}
+
+	return true
+}