You can use SQL Backup Pro to back up SQL server with encrypted connection or using Server Certificate

Encrypted Connection

To do this:

1. Open Registry Editor and locate HKEY_LOCAL_MACHINE\SOFTWARE\Red Gate\SQL Backup\BackupSettingsGlobal\(local) or <instance name>
2. Create a new DWORD type registry entry called ConnectionEncrypt and set the data value to 1.
3. From the Windows Services panel, stop and restart the SQL Backup Agent service.

Connect by trusting the Server Certificate 

To do this:

1. Open Registry Editor and locate HKEY_LOCAL_MACHINE\SOFTWARE\Red Gate\SQL Backup\BackupSettingsGlobal\(local) or <instance name>
2. Create a new DWORD type registry entry called ConnectionTrustServerCertificate and set the data value to 1.
3. From the Windows Services panel, stop and restart the SQL Backup Agent service.

To reinstate default connection, set the data value to 0 or delete the ConnectionTrustServerCertificate and ConnectionEncrypt entry.