This function is used to initialize the seed for the RC4 algorithm
CREATE FUNCTION dbo.fnInitRc4
(
@Pwd VARCHAR(256)
)
RETURNS @Box TABLE (i TINYINT, v TINYINT)
AS
BEGIN
DECLARE @Key TABLE (i TINYINT, v TINYINT)
DECLARE @Index SMALLINT, @PwdLen TINYINT
SELECT @Index = 0, @PwdLen = LEN(@Pwd)
WHILE @Index <= 255
BEGIN
INSERT @Key
(
i,
v
)
VALUES (
@Index,
ASCII(SUBSTRING(@Pwd, @Index % @PwdLen + 1, 1))
)
INSERT @Box
(
i,
v
)
VALUES (
@Index,
@Index
)
SELECT @Index = @Index + 1
END
DECLARE @t TINYINT, @b SMALLINT
SELECT @Index = 0, @b = 0
WHILE @Index <= 255
BEGIN
SELECT @b = (@b + b.v + k.v) % 256
FROM @Box AS b
INNER JOIN @Key AS k ON k.i = b.i
WHERE b.i = @Index
SELECT @t = v
FROM @Box
WHERE i = @Index
UPDATE b1
SET b1.v = (SELECT b2.v FROM @Box b2 WHERE b2.i = @b)
FROM @Box b1
WHERE b1.i = @Index
UPDATE @Box
SET v = @t
WHERE i = @b
SELECT @Index = @Index + 1
END
RETURN
END
ANd this function does the encrypt/decrypt part
CREATE FUNCTION dbo.fnEncDecRc4
(
@Pwd VARCHAR(256),
@Text VARCHAR(8000)
)
RETURNS VARCHAR(8000)
AS
BEGIN
DECLARE @Box TABLE (i TINYINT, v TINYINT)
INSERT @Box
(
i,
v
)
SELECT i,
v
FROM dbo.fnInitRc4(@Pwd)
DECLARE @Index SMALLINT,
@i SMALLINT,
@j SMALLINT,
@t TINYINT,
@k SMALLINT,
@CipherBy TINYINT,
@Cipher VARCHAR(8000)
SELECT @Index = 1,
@i = 0,
@j = 0,
@Cipher = ''
WHILE @Index <= DATALENGTH(@Text)
BEGIN
SELECT @i = (@i + 1) % 256
SELECT @j = (@j + b.v) % 256
FROM @Box b
WHERE b.i = @i
SELECT @t = v
FROM @Box
WHERE i = @i
UPDATE b
SET b.v = (SELECT w.v FROM @Box w WHERE w.i = @j)
FROM @Box b
WHERE b.i = @i
UPDATE @Box
SET v = @t
WHERE i = @j
SELECT @k = v
FROM @Box
WHERE i = @i
SELECT @k = (@k + v) % 256
FROM @Box
WHERE i = @j
SELECT @k = v
FROM @Box
WHERE i = @k
SELECT @CipherBy = ASCII(SUBSTRING(@Text, @Index, 1)) ^ @k,
@Cipher = @Cipher + CHAR(@CipherBy)
SELECT @Index = @Index +1
END
RETURN @Cipher
END
-- returns encrypted password
Select dbo.fnEncDecRc4('sqllover', 'harsh_athalye')
output (encrypted password):
---------------
eN¨6u(
-- decrypt it using same key
select dbo.fnEncDecRc4('sqllover', 'eN¨6u(')
output
-----------------
harsh_athalye
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