make required bigint helper public and remove ExplicitZero from SwapEndianess

utils.go

@@ -11,21 +11,21 @@ func SwapEndianness(b []byte) []byte {
 	for i := range b {
 		o[len(b)-1-i] = b[i]
 	}
-	return ExplicitZero(o)
+	return o
 }
 
 // BigIntToBytes converts a *big.Int into a byte array in Little-Endian
 func BigIntToBytes(blen int, bi *big.Int) []byte {
 	// TODO make the length depending on the tree.hashFunction.Len()
 	b := make([]byte, blen)
-	copy(b[:], SwapEndianness(bi.Bytes()))
+	copy(b[:], ExplicitZero(SwapEndianness(bi.Bytes())))
 	return b[:]
 }
 
 // BytesToBigInt converts a byte array in Little-Endian representation into
 // *big.Int
 func BytesToBigInt(b []byte) *big.Int {
-	return new(big.Int).SetBytes(SwapEndianness(b))
+	return new(big.Int).SetBytes(ExplicitZero(SwapEndianness(b)))
 }
 
 // ExplicitZero returns a byte slice with a single zero byte if the input slice