One problem with the CHECK_SUM() (or BINARY_CHECKSUM()) functions is that the probability of a collision may not be sufficiently low for all applications (i.e. SQL Server has the CHECK_SUM () (or BINARY_CHECKSUM ()) functions for generating the checksum value computed over a row of a table, or over a list of expressions. However, you can choose other hashing algorithms depending on your workload and data to hash. For security purposes, it is advised to use the strongest hash function (SHA2_512). Refer toĪlthough, most hashing functions are fast, the performance of a hashing function depends on the data to be hashed and the algorithm used.
However, data hashing can come to your rescue. Does that mean creating an index on top of encrypted data is not possible?
How to use hashbytes for indexing encrypted data.Įncryption introduces randomization and in there is no way to predict the outcome of an encryption built-in.
However, in the case of security code for the credit card, hashing it is sufficient if only equality checks are done and the system does not need to know it’s real value.Įncryption is a two way process but hashing is unidirectional Thus the credit card number should be encrypted in the payment processing system.
The deciding factor when choosing to encrypt or hash your data comes after you determine if you'll need to decrypt the data for offline processing.Ī typical example of data that needs to be decrypted would be within a payment processing system is a credit card number. Another key difference is that encryption normally results in different results for the same text but hashing always produces the same result for the same text. The difference is that encrypted data can be decrypted, while hashed data cannot be decrypted. For this reason, hashing is often called one-way hashing.ĭuring application development, it might be useful to understand when to encrypt your data vs. There will be absolutely no way to determine what changed in the input or to learn anything about the content of an input by examining hash values. It is computationally unfeasible to reverse. Minor changes to the document will generate a very different hash result.
It is especially sensitive to small changes in the input. Here is a sample along with the return values commented in the next line :Ī good hashing algorithm has these properties: SQL Server has a built-in function called HashBytes to support data hashing. Different messages should generate different hash values, but the same message causes the algorithm to generate the same hash value. Another possible scenario is the need to facilitate searching data that is encrypted using cell level encryption or storing application passwords inside the database.Ĭan be used to solve this problem in SQL Server.Ī hash is a number that is generated by reading the contents of a document or message. A common scenario in data warehousing applications is knowing what source system records to update, what data needs to be loaded and which data rows can be skipped as nothing has changed since they were last loaded.