path_to_file

Specifies the complete path, including file name, of the file in which the certificate is to be saved. This can be a local path or a UNC path to a network location. The default is the path of the SQL Server DATA folder.

path_to_private_key_file

Specifies the complete path, including file name, of the file in which the private key is to be saved. This can be a local path or a UNC path to a network location. The default is the path of the SQL Server DATA folder.

encryption_password

Is the password that is used to encrypt the private key before writing the key to the backup file. The password is subject to complexity checks.

decryption_password

Is the password that is used to decrypt the private key before backing up the key.

If the private key is encrypted with a password in the database, the decryption password must be specified.

When you back up the private key to a file, encryption is required. The password used to protect the backed up certificate is not the same password that is used to encrypt the private key of the certificate.

To restore a backed up certificate, use the CREATE CERTIFICATEstatement.

Requires CONTROL permission on the certificate and knowledge of the password that is used to encrypt the private key. If only the public part of the certificate is backed up, requires some permission on the certificate and that the caller has not been denied VIEW permission on the certificate.

A. Exporting a certificate to a file

BACKUP CERTIFICATE sales05 TO FILE = 'c:\storedcerts\sales05cert';
GO

B. Exporting a certificate and a private key

BACKUP CERTIFICATE sales05 TO FILE = 'c:\storedcerts\sales05cert'
    WITH PRIVATE KEY ( FILE = 'c:\storedkeys\sales05key' , 
    ENCRYPTION BY PASSWORD = '997jkhUbhk$w4ez0876hKHJH5gh' );
GO

C. Exporting a certificate that has an encrypted private key

BACKUP CERTIFICATE sales09 TO FILE = 'c:\storedcerts\sales09cert' 
    WITH PRIVATE KEY ( DECRYPTION BY PASSWORD = '9875t6#6rfid7vble7r' ,
    FILE = 'c:\storedkeys\sales09key' , 
    ENCRYPTION BY PASSWORD = '9n34khUbhk$w4ecJH5gh' );
GO

Reference

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