A third-party sends us a large CSV, an export from their (non-SQL Server) database. Several encrypted columns from their database were exported to CSV without being decrypted first. Separately, they sent us the symmetric key which they used to encrypt those columns of data.
We can decrypt those columns of data using a .NET program and the AesManaged classes before we import it into SQL Server; but is it possible to skip that step and decrypt those columns of data using T-SQL with their symmetric key after the data has been imported? Are there any decryption utilities in SQL Server that accept an AES_256 key as a parameter?