HashBytes function in SQL Server (wrong MD5 result)

Question

I faced on a strange problem with a SQL Server function HashBytes.

I have a column Password in my Users table (nvarchar(32), not null).

The user's password is 123456 which is e10adc3949ba59abbe56e057f20f883e in MD5 and this value is stored in the column.

I am trying to get MD5 hash function of e10adc3949ba59abbe56e057f20f883e which is actually 14e1b600b1fd579f47433b88e8d85291 (you may check it here), however in my SQL Server query, I get a totally another result:

SELECT TOP 1
   Password,
   lower(convert(nvarchar(32), HashBytes('MD5', '123456'), 2)) AS md5pass1,
   lower(convert(nvarchar(32), HashBytes('MD5', 'e10adc3949ba59abbe56e057f20f883e'), 2)) AS md5pass2,
   lower(convert(nvarchar(32), HashBytes('MD5',  Password), 2)) AS md5pass3
FROM Users

Result is:

and I expect to get '14e1b600b1fd579f47433b88e8d85291' as a result...

I appreciate you helping me!

Answer 1

You cannot hash text, you can only hash bytes. HashBytes converts the input string to bytes first. The conversion depends on whether the data type is a Unicode type. I guess that Password is nvarchar and I see that your literals are varchar.

Decide which one you want and use it consistently.

Answer 2

The root cause is that nvarchar you used is unicode. Get correct result once it converted to non-unicode varchar. Since it's password why not use varchar directly.