Character mask output data on select

Question

I'm using SQL Server 2008.

I would like to character mask the output data of a query.

This is my data from a column on a table when doing a select:

column1

384844033434

743423547878

111224678885

I would like an output like this:

column1

384xxxxxx434

743xxxxxx878

111xxxxxx885

How can I do this?

Answer 1

You would have to use a view, and deny all users SELECT access to the underlying table.

Your view would look something like

SELECT 
     SUBSTRING(x.SecurityNumber,1,3) + 
     'xxxxx' + 
     SUBSTRING(x.SecurityNumber,LEN(x.SecurityNumber) - 2, LEN(x.SecurityNumber))
     AS column1
FROM underlyingTable x

You could then grant your users SELECT access to just this view and have the out masked in the way you described.

If you wanted your client software to be able to insert or update data in this table, you would use an INSTEAD OF INSERT or INSTEAD OF UPDATE trigger to update the base table.

Answer 2

From SQL Server 2016+ you could use Dynamic Data Masking feature.

Dynamic data masking limits sensitive data exposure by masking it to non-privileged users. Dynamic data masking helps prevent unauthorized access to sensitive data by enabling customers to designate how much of the sensitive data to reveal with minimal impact on the application layer. It’s a data protection feature that hides the sensitive data in the result set of a query over designated database fields, while the data in the database is not changed. Dynamic data masking is easy to use with existing applications, since masking rules are applied in the query results. Many applications can mask sensitive data without modifying existing queries.

CREATE TABLE #tab(ID INT IDENTITY(1,1), column1 VARCHAR(12));

INSERT INTO #tab(column1)
VALUES('384844033434'),('743423547878'),('111224678885');

SELECT * FROM #tab;

Output:

╔════╦══════════════╗
║ ID ║   column1    ║
╠════╬══════════════╣
║  1 ║ 384844033434 ║
║  2 ║ 743423547878 ║
║  3 ║ 111224678885 ║
╚════╩══════════════╝

ALTER TABLE #tab
ALTER COLUMN column1 VARCHAR(12) MASKED WITH (FUNCTION = 'partial(3,"xxxxxx",3)');

SELECT * FROM #tab;

Output:

╔════╦══════════════╗
║ ID ║   column1    ║
╠════╬══════════════╣
║  1 ║ 384xxxxxx434 ║
║  2 ║ 743xxxxxx878 ║
║  3 ║ 111xxxxxx885 ║
╚════╩══════════════╝

LiveDemo

Answer 3

If you know how long your field of data will be, then you can use the static version that the other answer will produce, but you can always create a function to generate this:

CREATE FUNCTION MixUpCharacters
(
    @OrigVal varchar(max)
)
RETURNS varchar(max)
AS
BEGIN

DECLARE @NewVal varchar(max)
DECLARE @OrigLen int
DECLARE @LoopCt int
DECLARE @Part varchar(max) = ''
Declare @PartLength int

SET @NewVal = ''
SET @OrigLen = DATALENGTH(@OrigVal)
SET @LoopCt = 1

SET @Part = SUBSTRING(@OrigVal, 4, len(@OrigVal)-6)
set @PartLength = LEN(@Part)

WHILE @LoopCt <= @PartLength
    BEGIN
        -- Current length of possible characters
        SET @NewVal = @NewVal + 'X'

        -- Advance the loop
        SET @LoopCt = @LoopCt + 1
    END

    Return REPLACE(@OrigVal, @Part, @NewVal)
END

For this function you will pass in the values that you want to mask. So your query would be:

declare @temp table
(
    col1 varchar(50)
)

insert into @temp
values ('384844033434'), ('743423547878'), ('111224678885')

select dbo.MixUpCharacters(col1) col1
from @temp

See SQL Fiddle with Demo

The result would be:

|         COL1 |
----------------
| 384XXXXXX434 |
| 743XXXXXX878 |
| 111XXXXXX885 |

Or here is a way to do it with recursive CTE:

;with data(col1) as
(
    select '384844033434'
    union all
    select '7434235878'
    union all
    select '111224678885'
),
s1 (col1,  repfull) as
(
    select col1, 
        SUBSTRING(col1, 4, len(col1)-6) repfull
    from data
),
s2 (col1, item, repfull, r) as
(
    select col1,
        cast('x' as varchar(max)),
        right(repfull, LEN(repfull)-1),
        repfull
    from s1
    union all
    select col1,  
        'x'+ cast(item as varchar(max)),
        right(repfull, LEN(repfull)-1),
        r
    from s2
    where len(repfull) >0
)
select REPLACE(col1, r, item) newValue
from
(
    select col1, item, R,
        ROW_NUMBER() over(partition by col1 order by len(item) desc) rn
    from s2
) src
where rn = 1

See SQL Fiddle with Demo

Answer 4

A simple select query would return just what it's on the table, no matter if it's encrypted or not.

So, I think you can not do this on the database level.

For your requirement, you would need a bidirectional encryption algorithm to use in your application, so you can encrypt data before saving it encrypted on the database, and get the encrypted information from the database and decrypt it on your applicaition.

Answer 5

very simple bro

SELECT CONCAT (SUBSTR('Your string',1,3),LPAD(SUBSTR('Your string',-3),LENGTH('Your string')-1,'*')) RESULT FROM dual

output :

You*******ing

if it is num type convert to char

Answer 6

If you want to mask field which you dont know about field's length. You can upgrade bluefeet's code like this:

ALTER FUNCTION MixUpCharacters
(
    @OrigVal varchar(MAX)
)
RETURNS varchar(MAX)
AS
BEGIN

DECLARE @NewVal NVARCHAR(MAX)
DECLARE @OrigLen INT
DECLARE @LoopCt INT
DECLARE @Part NVARCHAR(MAX) = ''
DECLARE @PartLength INT     -- MastLength
DECLARE @PartStartIndex INT -- MaskStartIndex

SET @NewVal = ''
SET @LoopCt = 1
SET @OrigLen = LEN(@OrigVal)

IF(@OrigLen = 1)
    BEGIN
        RETURN 'X'
    END
IF(@OrigLen < 6)
    BEGIN
        SET @PartStartIndex = @OrigLen / 2
        SET @PartLength = @OrigLen - @PartStartIndex
        SET @Part = SUBSTRING(@OrigVal, @PartStartIndex,  @PartLength)
    END
ELSE IF(@OrigLen < 8)
    BEGIN
        SET @PartStartIndex = 3
        SET @PartLength = @OrigLen - @PartStartIndex - 1
        SET @Part = SUBSTRING(@OrigVal, @PartStartIndex,  @PartLength)
    END
ELSE
    BEGIN
        SET @PartStartIndex = 4
        SET @PartLength = @OrigLen - @PartStartIndex - 2
        SET @Part = SUBSTRING(@OrigVal, @PartStartIndex,  @PartLength)
    END

WHILE @LoopCt <= @PartLength
    BEGIN
        -- Current length of possible characters
        SET @NewVal = @NewVal + 'X'

        -- Advance the loop
        SET @LoopCt = @LoopCt + 1
    END

    RETURN REPLACE(@OrigVal, @Part, @NewVal)
END

You can test like this:

SELECT dbo.MixUpCharacters('1')
UNION ALL
SELECT dbo.MixUpCharacters('12')
UNION ALL
SELECT dbo.MixUpCharacters('123')
UNION ALL
SELECT dbo.MixUpCharacters('1234')
UNION ALL
SELECT dbo.MixUpCharacters('12345')
UNION ALL
SELECT dbo.MixUpCharacters('123456')
UNION ALL
SELECT dbo.MixUpCharacters('1234567')
UNION ALL
SELECT dbo.MixUpCharacters('12345678')
UNION ALL
SELECT dbo.MixUpCharacters('123456789')
UNION ALL
select dbo.MixUpCharacters('1234567890')
UNION ALL
select dbo.MixUpCharacters('12345678910')

RESULTS:

X
X2
XX3
1XX4
1XXX5
12XX56
12XXX67
123XX678
123XXX789
123XXXX890
123XXXXX910

Answer 7

This also works for masking output when retrieve.

SELECT CONCAT(SUBSTRING(column1, 1, 3),'xxxxxx',SUBSTRING(column1, 10, 3)) FROM tableName;

If the value length is not fixed, can use the below.

SELECT CONCAT(SUBSTRING(column1, 1, 3),'xxxxxx',SUBSTRING(column1, LEN(column1)-2, 3)) FROM tableName;