An asymmetric key is a securable entity at the database level. In its default form, this entity contains both a public key and a private key. When executed without the FROM clause, CREATE ASYMMETRIC KEY generates a new key pair. When executed with the FROM clause, CREATE ASYMMETRIC KEY imports a key pair from a file or imports a public key from an assembly.
By default, the private key is protected by the database master key. If no database master key has been created, a password is required to protect the private key. If a database master key does exist, the password is optional.
The private key can be 512, 1024, or 2048 bits long.