to the compressed data. Another factor to be aware of is how well the encryption algorithm can cope with errors in the backup media. When using AES with CBC (Cipher Block Chaining) mode a single bit-error in the encrypted stream will cause the entire 256-bit block containing the error and the following block to be indecipherable. After those two blocks the decoder should be able to recover and continue decrypting the data although these two bad blocks could severely affect how well the system can recover files from the decrypted stream. Key Management You must bear in mind that with encryption the key is everything. If you start writing encrypted backups for a month or so, then lose they key you were using - then all of othat backup data is useless. Don't even think about trying to decode it without the key. So in this respect you must keep your key data just as secure as you would your backup media. Print out the key data on paper and store it in the company safe - and maybe an offsite secure location as well. If you have a very long key file, then save it to a number of different types of media (CD-ROM, USB drive, floppy disk) and store them somewhere safe. Keys should be changed on a regular basis, and when employees and contractors leave the company. But be aware that losing a key will cause the loss of the backups made with that key. Always keep