Beyond SHA1: Using HASHBYTES for Secure Hashing in MS SQL (with Caution)

• Deprecated: HASHBYTES with algorithms like SHA1 and MD5 is deprecated since SQL Server 2016. It's recommended to use the stronger and more secure alternatives like SHA2_256 or SHA2_512 whenever possible.
• Different Output: Unlike SHA1(), which returns a standard 40-character hexadecimal string, HASHBYTES with SHA1 returns a binary value by default. You need additional steps to convert it to a human-readable format.

Here's an example of how to use HASHBYTES to generate a SHA1 hash in MS SQL:

DECLARE @data NVARCHAR(MAX) = 'This is some sample data.';
SELECT CONVERT(VARCHAR(40), HASHBYTES('SHA1', CONVERT(VARBINARY(MAX), @data))) AS Hash;

This code:

1. Declares a variable @data to store the string you want to hash.
2. Uses HASHBYTES with the SHA1 algorithm and converts the input data (@data) to VARBINARY format before hashing.
3. Converts the resulting binary hash to a VARCHAR(40) string using CONVERT. This ensures enough space for the 40-character hexadecimal representation of the hash.
4. Aliases the result as Hash for better readability.

Important points to remember:

• Using SHA1 with HASHBYTES is not recommended for new development due to deprecation and security concerns. Consider using SHA2_256 or SHA2_512 instead.
• The provided example converts the hash to a hexadecimal string. You might need to adjust the conversion depending on your specific needs.