DECLARE @ToAllGoodPeople TABLE
        (
        RowNum INT,
        Cypher  VARCHAR(100)
        )

 INSERT INTO @ToAllGoodPeople
        (RowNum, Cypher)
 SELECT 1,'8.1.16.16.25.27.2.9.18.20.8.4.1.25' UNION ALL
 SELECT 2,'1.14.4.27.7.15.15.4.23.9.12.12' UNION ALL
 SELECT 3,'20.15.27.1.12.12'

 SELECT REPLACE((SELECT CHAR(SUBSTRING('.'+p2.Cypher,N+1,CHARINDEX('.',p2.Cypher+'.',N)-N)+64)
                  FROM dbo.Tally t
                 CROSS JOIN @ToAllGoodPeople p2
                 WHERE p1.RowNum = p2.RowNum
                   AND t.N <= LEN(p2.Cypher)+1
                   AND SUBSTRING('.'+p2.Cypher,t.N,1) = '.'
                 ORDER BY t.N
                   FOR XML PATH(''))
        ,'[',' ')
   FROM @ToAllGoodPeople p1
  GROUP BY p1.RowNum
  ORDER BY p1.RowNum

...
 SELECT REPLACE((SELECT CHAR(SUBSTRING('.'+p2.Cypher,N+1,CHARINDEX('.',p2.Cypher+'.',N)-N)+64)
                  FROM dbo.Tally t
...

...
 SELECT REPLACE((SELECT CHAR(SUBSTRING('.'+p2.Cypher,N+1,CHARINDEX('.',p2.Cypher+'.',N)-N)+64)
                  FROM (SELECT number AS N FROM master.dbo.spt_values WHERE type = 'P') t
...