Generate anonymous ids in JOIN query - mysql

Question

The task is to extract customer and order data from a sensitive system. Data is stored in a MySQL database.
A customer can be associated with many orders. A simple LEFT JOIN gives me exactly what I require:
---------------------------------------------------------
| customer_id | order_id | order_quantity | order_value |
---------------------------------------------------------
| 1 | 100 | 3 | 100.00 |
| 1 | 105 | 12 | 400.00 |
| 2 | 103 | 2 | 75.00 |
---------------------------------------------------------
However, in the generated extract, I'm not allowed to reveal the customer_id nor the order_id. Instead, these ids need to be replaced by random, anonymized identifiers generated at the time of data export.
The relationship between customers and their orders still needs to be maintained in the resulting, extracted data export.
Desired outcome:
-------------------------------------------------------------------
| anon_customer_id | anon_order_id | order_quantity | order_value |
-------------------------------------------------------------------
| xyz | abc123 | 3 | 100.00 |
| xyz | def567 | 12 | 400.00 |
| pqr | hij890 | 2 | 75.00 |
-------------------------------------------------------------------
Is there a way to generate anon_customer_id and anon_order_id as part of the SELECT I'm running to build the data result?

Answer 1

One option would be using MySQL's native encryption methods like SHA1 or SHA2 and make a VIEW which you query and join with.
I've choosen to use SHA 512 because it has a very low probability different data could generate the same hash.
CREATE VIEW Table1_VIEW AS (
SELECT
<table>.*
, SHA2(<table>.customer_id, 512) AS anon_customer_id
, SHA2(<table>.order_id, 512) AS anon_order_id
FROM
<table>
)
Query and result
SELECT
*
FROM
Table1_VIEW
| customer_id | order_id | order_quantity | order_value | anon_customer_id | anon_order_id |
| ----------- | -------- | -------------- | ----------- | -------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------- |
| 1 | 100 | 3 | 100 | 4dff4ea340f0a823f15d3f4f01ab62eae0e5da579ccb851f8db9dfe84c58b2b37b89903a740e1ee172da793a6e79d560e5f7f9bd058a12a280433ed6fa46510a | 643c30f73a3017050b287794fc8c5bb9ab06b9ce38a1fc58df402a8b66ff58f69bf0a606ae17585352a0306f0e9752de8c5c064aed7003f52808b43ff992a603 |
| 1 | 105 | 12 | 400 | 4dff4ea340f0a823f15d3f4f01ab62eae0e5da579ccb851f8db9dfe84c58b2b37b89903a740e1ee172da793a6e79d560e5f7f9bd058a12a280433ed6fa46510a | 03d25c7071bce10d6b462d53854b969d9f61b982e3aee8771bdcca1ecb70495574e6929042f52e859ee9a253b58f776514180ff16e1338f5505e86c7ff328f72 |
| 2 | 103 | 2 | 75 | 40b244112641dd78dd4f93b6c9190dd46e0099194d5a44257b7efad6ef9ff4683da1eda0244448cb343aa688f5d3efd7314dafe580ac0bcbf115aeca9e8dc114 | 947de04bfae0bf062a66fc055d4c284c9779793d9bd58833ee7549fde1ff1effaf7aefdbc6c90ed0ac86c0acc82329e7c057d900c28ea7ed4724486f717ee38d |
demo
p.s You can also directly use SHA2() directly in a JOIN offcource.
Example Query
SELECT
table11.*
, SHA2(table11.customer_id, 512) AS anon_customer_id
, SHA2(table11.order_id, 512) AS anon_order_id
FROM
Table1 table11
LEFT JOIN
Table1 table12
ON
table11.customer_id = table12.customer_id
demo
MYSQL 5.7+ only
If you have atleast MySQL 5.7+ you have a even better option. Which is generated columns
CREATE TABLE Table1 (
`customer_id` INTEGER,
`order_id` INTEGER,
`order_quantity` INTEGER,
`order_value` INTEGER,
anon_customer_id VARCHAR(255) AS ( SHA2(Table1.customer_id, 512) ) VIRTUAL,
anon_order_id VARCHAR(255) AS ( SHA2(Table1.order_id, 512) ) VIRTUAL
);
demo
Edit because of the comment from Louis
my point was that someone will be able to extract the sensitive
customer id after it's hashed. Simply by calculating hashes of all
possible or likely customer id and seeing which is the same. If the
customer ID is not an increasing number with predictable range but
some randomly assigned very large number or indeed a long random
string it might be better
This is very true what you can do is add more entropy to the hash so the real id arn't that easy to bruteforce annymore.
In this case you add atleast 52 characters (datetime(6) and the reverse one) as entropy that should be more then enough to protect against bruteforces for (some) years to come.
CREATE VIEW Table1_VIEW_more_entropy AS (
SELECT
Table1.*
, SHA2(CONCAT_WS(':', Table1.id, Table1.date_created, REVERSE(Table1.date_created), Table1.customer_id), 512)
, SHA2(CONCAT_WS(':', Table1.id, Table1.date_created, REVERSE(Table1.date_created), Table1.order_id), 512)
FROM
Table1
);
see demo

Answer 2

You could use any hash function, for example, MD5:
SELECT MD5(customer_id) AS anon_customer_id FROM customers;
But be aware though, MD5 is not very secure: https://security.stackexchange.com/questions/19906/is-md5-considered-insecure