--**************************************
--     
-- Name: RC4 stored proc functions
-- Description:Implements standard RC4 a
--     lgorithms using memory tables through sq
--     l functions. No active x needed. Speed c
--     an be improved by pre generating and sto
--     ring key state table.
-- By: Stuart Dee
--
-- Inputs:key and data
--
-- Returns:encrypted/decrypted data stri
--     ng
--
--This code is copyrighted and has-- limited warranties.Please see http://
--     www.Planet-Source-Code.com/vb/scripts/Sh
--     owCode.asp?txtCodeId=587&lngWId;=5--for details.--**************************************
--     

CREATE FUNCTION rc4_fnEncryption
 (@p_cKey varchar(255),@p_cData varchar(255)) 
RETURNS varchar(255)
AS 
    BEGIN 
    DECLARE @stateTable TABLE (PKstate int PRIMARY key,statevalue int)
    DECLARE @loopCounter int,
    	 @dataLen int,
    	@Iindex int,
    	@jIndex int,
    	@stateValue int,
    	@stateJvalue int,
    	@KIndex int,
    	@KValue int,
    	@cipherValue int,
    	@cipherChar char(1),
    	@cipherResults varchar(255)
    SELECT @loopCounter=1,
    	 @dataLen=LEN(@p_cData)+1,
    	@Iindex=0,
    	@JIndex=0,
    	@cipherResults=''
    -- Initialise state Table
    INSERT INTO @stateTable
    (pkState,
     statevalue)
    SELECT *
    FROM dbo.rc4_fnInitialise(@p_cKey)
    WHILE @loopCounter<@dataLen
        BEGIN
        	SET @iIndex=(@iIndex+1) % 256
        	SELECT @statevalue=statevalue
        	FROM @stateTable
        	WHERE PKstate=@iIndex
        	SET @jIndex=(@jIndex+@stateValue) % 256
        	SELECT @stateJvalue=stateValue
        	FROM @stateTable
        	WHERE PKstate=@JIndex
        	UPDATE @stateTable
        	SET stateValue=@stateJvalue
        	WHERE PKstate=@IIndex
        	UPDATE @stateTable
        	SET stateValue=@stateValue
        	WHERE PKstate=@JIndex
        	SET @kIndex=(@stateValue+@stateJvalue) % 256
        	SELECT @kValue=stateValue
        	FROM @stateTable
        	WHERE PKstate=@kIndex
        	SET @cipherChar=SUBSTRING(@p_cData,@loopCounter,1)
        	SET @cipherValue=ASCII(@cipherChar) ^@kIndex
        	SET @cipherResults=@cipherResults+CHAR(@cipherValue)
        	SET @loopCounter=@loopCounter+1
    END

    RETURN @cipherResults
END

GO
SET QUOTED_IDENTIFIER OFF 
GO
SET ANSI_NULLS ON 
GO
SET QUOTED_IDENTIFIER OFF 
GO
SET ANSI_NULLS OFF 
GO
CREATE FUNCTION rc4_fnInitialise
 (@p_cKey varchar(255)) 
RETURNS @stateTable TABLE (PKstate int PRIMARY KEY identity(1,1),statevalue int)
AS 
    BEGIN 
    DECLARE @LoopCounter int,
    	 @keyAscii int,
    	 @charStart int,
    	 @keyLength int,
    	 @stateIndex int,
    	 @stateValue int,
    	 @keyValue int,
    	 @swapValue Int,
    	 @swapIdxValue int
    DECLARE @keyTable TABLE (PKEncrypt int IDENTITY(1,1) PRIMARY key , keyvalue int)
    --DECLARE @stateTable TABLE (PKState int
    --      IDENTITY(1,1) primary key, stateValue i
    --     nt)
    SELECT @loopCounter=1,
    	@keyLength=LEN(@p_cKey)
    -- populate key & state tables
    WHILE	@loopCounter<257
        BEGIN
        	SET @charStart=(@loopCounter %@keyLength)+1
        	SET @keyAscii=ASCII(SUBSTRING(@p_cKey,@charStart,1))
        	INSERT INTO @keyTable
        	(keyValue)
        	VALUES
        	(@keyAscii)
        	INSERT INTO @stateTable
        	(stateValue)
        	VALUES
        	(@loopCounter)
        	SET @loopCounter=@loopCounter+1
    END

    SELECT @loopCounter=1,
    	 @stateIndex=0
    WHILE	@loopCounter<257
        BEGIN
        	SELECT @stateValue=stateValue
        	FROM @stateTable
        	WHERE pkState=@loopCounter
        	SELECT @keyValue=keyvalue
        	FROM @keyTable
        	WHERE pkEncrypt=@loopCounter
        	SET @stateIndex=(@stateIndex+@stateValue+@keyValue) % 256 
        	SET @swapValue=@stateValue
        	SELECT @swapIdxValue=stateValue
        	FROM @stateTable
        	WHERE pkState=@stateIndex
        	UPDATE @stateTable
        	SET stateValue=@swapIdxValue
        	WHERE pkstate=@loopCounter
        	UPDATE @stateTable
        	SET stateValue=@swapValue
        	WHERE pkstate=@stateIndex
        	SET @loopCounter=@loopCounter+1
    END

    RETURN
END

GO
SET QUOTED_IDENTIFIER OFF 
GO
SET ANSI_NULLS ON 
GO