This is a simple RD4 encryption stored procedure.  It beats using a cast as varbinary!

This is a simple RD4 encryption stored procedure. It's nice because it uses the same procedure to encrypt and decrypt and it beats using a cast as varbinary!



/*--------------------------------------------------------------------------
AUTHOR: Suman Chakrabarti
DATE: 4/29/2003
DESC: This is a simple RD4 Encryption algorithm
--------------------------------------------------------------------------*/
CREATE PROCEDURE uspEncryptDecrypt
(
    @sKey  varchar(100),
    @sValue varchar(100),
    @sReturnVal varchar(100) output
)
AS

SET QUOTED_IDENTIFIER ON

SET ANSI_NULLS ON

DECLARE @iKeyLen int
DECLARE @counter int
DECLARE @iLoopCount int

create table #sKey ([id] int not null identity primary key, col int)
create table #sBox ([id] int not null identity primary key, col int)

SET @iKeyLen = Len(@sKey)
SET @counter = 0
-- PRINT @iKeyLen

-- setup the Keybox ------------------------------------------------------
WHILE @counter < @iKeyLen
BEGIN
    INSERT INTO #sKey (col) VALUES (ASCII(SUBSTRING(@sKey, (@counter % @iKeyLen)+1, 1)))
    SET @counter = @counter + 1
END

SET @iLoopCount = Floor(255 / (@iKeyLen-1))

WHILE @counter < @iLoopCount
BEGIN
    INSERT INTO #sKey (col) SELECT col FROM #sKey WHERE [id] < @iKeyLen+1 ORDER BY [id]
    SET @counter = @counter + 1
END
DELETE FROM #sKey WHERE [id] > 255

-- setup the Sandbox --------------------------------------------------------
SET @counter = 0
WHILE @counter < 256
BEGIN
    INSERT INTO #sBox (col) VALUES (@counter)
    SET @counter = @counter + 1
END

-- Begin the encryption routine ---------------------------------------------
DECLARE @iVal int, @tmpSwap int
DECLARE @iValueLen int
DECLARE @i int, @j int, @k int, @iFinal1 int, @iFinal2 int

SET @counter = 0
SET @iVal = 0
WHILE @counter < 255
BEGIN
    SELECT @iVal = (@iVal + k.col + b.col) % 256 FROM #sKey k, #sBox b WHERE k.[id] = @counter + 1
    SELECT @tmpSwap = col FROM #sBox WHERE [id] = @counter+1
    UPDATE #sBox SET col = @iVal WHERE [id] = @counter+1
    UPDATE #sBox SET col = @tmpSwap WHERE [id] = @iVal
    SET @counter = @counter + 1
END

SET @i = 0
SET @j = 0
SET @i = (@i + 1) % 256

SELECT @j = (@j + col) % 256 FROM #sBox where [id] = @i
SELECT @iVal = col FROM #sBox WHERE [id] = @j
SELECT @tmpSwap = col FROM #sBox WHERE [id] = @i
UPDATE #sBox SET col = @iVal WHERE [id] = @i
UPDATE #sBox SET col = @tmpSwap WHERE [id] = @j

SELECT @iFinal1 = col FROM #sBox WHERE [id] = @i
SELECT @iFinal2 = col FROM #sBox WHERE [id] = @j

--select CHAR(col) from #sBox
--SELECT @k = col % 256 FROM #sBox WHERE [id] = (@iFinal1 + @iFinal2)
-- print 'k: ' + CAST(@k as varchar(20))
SET @k = 1

-- [EnDe]Crypt the value ---------------------------------------------------------------
DECLARE @cipher varchar(500)
DECLARE @cipherBy int

SET @counter = 1
SET @iValueLen = Len(@sValue)
SET @cipher = ''

WHILE @counter < @iValueLen+1
BEGIN
    SET @cipherby = ASCII(SUBSTRING(@sValue, @counter, 1)) ^ @k
    SET @cipher = @cipher + CHAR(@cipherby)
    SET @counter = @counter + 1
END

SELECT @sReturnVal = @cipher

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