{"id":2465,"date":"2014-07-07T11:00:35","date_gmt":"2014-07-07T15:00:35","guid":{"rendered":"http:\/\/sqlity.net\/en\/?p=2465"},"modified":"2014-11-13T12:21:02","modified_gmt":"2014-11-13T17:21:02","slug":"hashbytes","status":"publish","type":"post","link":"https:\/\/sqlity.net\/en\/2465\/hashbytes\/","title":{"rendered":"HASHBYTES: How to Calculate a Cryptographic Hash in T-SQL"},"content":{"rendered":"
\n

Introduction<\/h3>\n

\nCryptographic hash functions<\/a> can be used in many situations, e.g. to store passwords securely or to provide a searchable key for encrypted values. If you have to calculate a hash value in the application layer, you can use one of the libraries available in your language of choice. Sometimes however you have to calculate the hash value in T-SQL. For those cases, SQL Server provides the HASHBYTES<\/span> function.\n<\/p>\n

A HASHBYTES Example<\/h3>\n

\nThe HASHBYTES<\/span> function takes two parameters. The first parameter is the name of the algorithm to be used. The second parameter is the string that is used as input for the hash function:\n<\/p>\n

\n[sql]\nDECLARE @AString NVARCHAR(MAX) = 'Hello World';<\/p>\n

SELECT HASHBYTES('SHA2_512',@AString) AS [@AString (1)];
\n[\/sql]\n<\/p><\/div>\n

\nThe hash calculation does not automatically introduce a salt<\/a>, but rather does a straightforward hash value calculation. That means that the same input value will always produce the same output value:\n<\/p>\n

\n\"HASHBYTES<\/a>\n<\/p>\n

HASHBYTES Limitations<\/h3>\n

\nThere are two limitations to the HASHBYTES<\/span> function that you need to be aware of. The first limitation is that there is only a fairly small selection of available hash algorithms:\n<\/p>\n