... Decrypt encrypted backup files

You can decrypt encrypted backup files in this way:

·If the backup files were encrypted with the proprietary SecurDat technology (see SecurDat Encryption option) then there are 2 possibilities:  
1) While holding down the Ctrl key drag and drop a folder with encrypted files or one or more encrypted files onto the SecurDat main window: This will display the Decrypt dialog where you can input the password and then start the decrypting process.  
2) In the SecurDat Options menu click the Decrypt files menu item, or press Strg-Y in SecurDat: This will display a Windows file dialog where you can select one or more files to decrypt.  

·If the backup files were compressed and encrypted with the well known ZIP technology (see ZIP Encryption option) by SecurDat then there are also several possibilities.  
1) You can extract the ZIP archives compressed by SecurDat with one of the many existing programs for this purpose. You will then be asked to input a password if necessary. (A free program for to extract ZIP archives you can find for example here).  
2) If you restore backup files in SecurDat which were compressed to ZIP archives then a password dialog will be automatically displayed if the archives are encrypted.