looking at some legacy code, this is trying to "encrypt" an input string. Not the best way:

Code:
rawData=lcase(rawData)
encrypted=""
for iIdx=1 to len(rawData)
	encrypted=encrypted & chr(asc(mid(rawData,iIdx,1))+13)
next
C#:

Code:
rawData= Convert.ToString(rawData).ToLower();
encrypted= "";
for (var iIdx = 1; iIdx <= rawData.Length; iIdx++)
{
	encrypted= encrypted + (char)(Convert.ToInt32(rawData[iIdx - 1]) + 13);
}

I am wondering if there is a way to reverse the generated string in encrypted so I can get back the original input?