CREATE FUNCTION dbo.simpleencrypt (@input VARCHAR(10), @crypt TINYINT)
RETURNS VARCHAR(10)
	AS
		BEGIN
			DECLARE @result VARCHAR(10), @i INT, @tmp TINYINT
			SET @i=1
			SET @result=''
			WHILE @i<=LEN(@input)
	 			BEGIN
 					SET @tmp=ASCII(SUBSTRING(@input,@i,1))
 					SET @result=@result + CHAR(@tmp ^ @crypt)
 					SET @i=@i+1
 				END
			RETURN @result
		END
GO
SELECT dbo.simpleencrypt('FRANK',10)
SELECT dbo.simpleencrypt('LXKDA',10)
DROP FUNCTION dbo.simpleencrypt
           
---------- 
LXKDA

(1 row(s) affected)

           
---------- 
FRANK

(1 row(s) affected)

Irgendwie tendiere ich dazu, dies über das Front-End erledigen zu lassen und nicht über den Server.