Data Encryption - FAQ

Table of Contents


How can I tell if a job has been encrypted and by what method?

The Jobs in Storage Policy report will show a superscript E or an HE next to the job ID for jobs that have been software or hardware encrypted respectively.

What kind of performance hit can I expect from encryption?

Software encryption is a CPU intensive operation and can reduce your backup or auxiliary copy performance by an estimated 40%-50%. Note that this estimated performance hit is not applicable to deduplicated data as deduplication process discards all duplicate data and only encrypts data blocks that are unique in the entire deduplication database. Hence the performance hit for deduplicated data will be low.

Hardware encryption has a significantly less impact of about 10%.

Which is the most secure encryption algorithm?

RijnDael, by virtue of it being the Advanced Encryption Standard (AES), would be considered the most secure encryption algorithm. However, AES was selected based on a series of requirements of which security level was just one. All candidates for AES met or exceeded the security requirement. Serpent and Twofish ciphers were also AES candidates. Twofish is faster and Serpent is considered more secure.

Can I encrypt NDMP data during backup or auxiliary copy?

If the NDMP data is directed to a NDMP Remote Server-enabled MediaAgent for data protection or auxiliary copy you can software and hardware encrypt the data. For NDMP data sent directly to a filer-attached library only hardware encryption is supported. Filer direct Hardware encryption requires a 3rd party key management system.

Does encryption require a Certificate Authority?

Certificate Authority is required only for Asymmetric cryptography where different keys are used to encrypt (using private key) and decrypt (using public key) the data. All of our encryption is symmetric cryptography (the same key is used to encrypt and decrypt) ,so there is no need for a certificate or a certificate authority.

Asymmetric crypto is typically used when you are sending data over insecure lines (like over the internet) and the identity of entities at each end is not known, the CA helps validate the authenticity of that sent data so that malicious data is not sent. In our case, since there are known entities at both ends this issue does not exist.

We do not encrypt data set with a single key. Instead we generate a key for every chunk of data that is written which means there is an extremely minimal chance of the entire data being lost even if one key is compromised.

What is the cryptographic library used?

CommVault Cryptographic Library Version – 1.0 (FIPS 140-2 Certified)

What is the AES block mode of operation and IV management for encrypted data?

AES 256 - CBC mode. Each 64KB block is a single CBC chain. IVs are randomly generated using a ANSI 9.31 random number generator. There is no extra special management of IVs. They are included into the cipher text stream.

What integrity checks are performed on encrypted data?

Integrity for each data block up-to 64 KB is checked with CRC32.

Where does decryption occur?

Type of Encrypted Data Decryption Will Occur On
Hardware Hardware device
  • At the client upon restore
  • On the source MediaAgent during synthetic full (decrypted/re-encrypted automatically)
  • On the source MediaAgent during auxiliary copy of deduplicated data (re-encryption on the Source MediaAgent is an option requiring the offline encryption license)
  • On the source MediaAgent during auxiliary copy if re-encryption is selected. (decrypted then re-encrypted with select algorithm)
  • On the Media Explorer host when restoring data

How are user passwords encrypted, transmitted, and stored?

NetApp user passwords are encrypted using a proprietary algorithm and transmitted/stored only in encrypted format. External (Active Directory) user passwords are not stored.

What happens to encrypted data if you uninstall the license?

Existing data remains encrypted and can be recovered. New data will not have the option for encryption.

Does encryption have an impact on compression when writing to media?

Yes, by using encryption when performing backup operations, the data is effectively randomized. This means that the compression algorithms will not be as effective when compressing the encrypted data. So when this data gets written to media there will be a noticeable difference in the compression ratio.

Example: A tape with a Native capacity of 110GB which at one time got 190GB compressed may now only get 124GB written to the same tape when using encryption as well.

The amount of data that can be written to tape varies depending on the type of data getting written that is Image files will not be compressed as they are already considered compressed but a TXT file is highly compressible.

Auxiliary Copy

Where does Offline/Auxiliary copy encryption occur - at the source or target MediaAgent?

Offline Encryption performed during an auxiliary copy operation is performed at the source MediaAgent. This provides transmission path security.

If I enable encryption during both backup and offline/auxiliary copy – is the data encrypted twice?

No, the data is not encrypted twice. Data that has been encrypted by SnapProtect software is flagged. During an auxiliary copy operation the flag is checked and, if the data has already been encrypted, no additional software encryption is applied. Only data that has not been encrypted by NetApp will be encrypted during the auxiliary copy process.


If hardware encryption is enabled – will this further encrypt already encrypted data?

Yes, software encrypted data will be further encrypted if hardware encryption is enabled. We strongly recommend enabling one or the other – not both.

Can I restore hardware encrypted data using Media Explorer?

Yes, Media Explorer supports restore of hardware encrypted data from a supported drive.

What encryption-capable tape drives are supported?

Some tape drives such as, Ultrium (LTO-4 or later), are encryption-capable. Other drive types might also support encryption. However, to confirm encryption support, we recommend that you refer to the drive vendor’s documentation.

For more information on hardware encryption, see Hardware Encryption.

What happens to jobs if hardware encryption is selected but the drive does not support it?

The Hardware encryption option is enabled on the Storage Policy copy as a property of the data path. Hardware encryption is only applicable for supported Tape Devices. If the drive does not support hardware encryption and the option is selected, backups running to the drive will fail.

Do we support any third party encryption hardware?

Hardware encryption devices with their own key management software such as Network Appliances (formerly Decru’s) Datafort can be used. These inline devices are transparent to the data flow from NetApp. However, data written via these devices must be restored via these devices and it is the customer’s responsibility to provide and manage these devices.

Can NetApp set the encryption algorithm and key length for hardware encryption?

No, hardware encryption algorithm and key length is fixed by the hardware vendor. Most of the terms use AES-256 for FIPS compliance. NetApp can enable or disable hardware encryption. Any variance to algorithm or key length used is hardware vendor dependent.


How are keys derived?

Keys are generated from a random number generator. The random number generator we use is ANSI 9.31 It’s used to produce RSA key pair for the client, generate random 128-bit or 256-bit data encryption keys for every chunk and initial vectors (IV) for CBC chaining during data encryption.

What is the ANSI 9.31 implementation?

ANSI 9.31 is the standard for digital signatures based on the RSA algorithm. It requires the MDC-2 hash algorithm.

Refer to for more information.

Is a persistent seed used for the random number generator?

No. Various random OS-supplied data is used.

How often are keys changed for each system?

For Hardware Encryption, we generate a different random 128 or 256 key for every data chunk we write. Each job can contain multiple chunks, so each backup job can have multiple randomly generated keys. With multiple different keys the strength of the encryption is very high.

For SnapProtect software encryption, a new key is generated for each backup.

How are keys integrity checked?

Every key stored in the Database has CRC32 embedded. This is used only to check whether a key has been entered incorrectly. If an error is detected the user will be prompted to re-enter the pass phrase or check for network/media malfunction.

How are keys identified?

Keys are identified by their storage location in the database. We don’t embed IDs into the keys.

How are keys authenticated?

They are wrapped using AES Key Wrap Specification.

Refer to AES Key Wrap Specification for more details.

How are keys stored in the CommServe database?

Data encryption keys are stored in the database encrypted with RSA public key of the client. RSA private key of the client is stored encrypted either with a built-in pass-phrase or with the pass-phrase provided by user, depending on the settings.

Are keys stored anywhere else?

Keys can optionally be written to the backup media for manual recovery of data using Media Explorer.

How are keys backed up for disaster recovery purposes?

A regularly scheduled Export and Backup of the CommServe Database (DR Backup task) provides Disaster Recovery protection.

Who has access to the encryption keys?

No users are allowed access to the keys. Our keys are stored in the CommServe Database encrypted with RSA public key of the client. RSA private key of the client is stored encrypted either with a built-in pass-phrase or with the pass-phrase provided by user, depending on the settings. The user provided Pass Phrase is not stored anywhere. Only authorized users (configured from user management) can set and change these pass phrases. Pass phrases are never displayed in clear text.

How are keys destroyed when they are no longer needed?

When chunks are pruned (erased), the database entry and associated key for that chunk is deleted. Open keys in memory are deleted using memset().

How does deduplication affect data encryption?

Pass-phrase option is not supported with deduplication.

If you are creating a secondary copy from an encrypted-deduplicated source copy, the software automatically decrypts the deduplicated data during the creation of the secondary copy. Thus, if you wish to create a fully encrypted secondary copy of data from an encrypted-deduplicated source copy, ensure that the secondary copy is configured for re-encryption. Otherwise, the deduplicated portion of the data will remain decrypted.

Pass Phrase

  • The Pass-Phrase feature is deprecated. For similar functionality, use Privacy.
  • Clients with existing Pass-Phrase configurations are supported.

When would I use a Pass Phrase?

A Pass Phrase can be enabled and set differently for each client providing unique protection of the encryption keys for data. For example; you may want to provide unique Pass Phrases for certain financial data servers and personnel file servers. When restoring Pass Phrase encrypted data, you must manually provide the Pass Phrase. If you lose the Pass Phrase, the encrypted data is unrecoverable.

Can I change the Pass Phrase?

Yes, you can change the Pass Phrase at anytime. You do not need to maintain the older Pass Phrase.

See Reset a Pass Phrase for instructions.

How are Pass Phrases used to authenticate a restore?

They are used to decrypt the RSA private key of the client. The RSA private key is then used to decrypt the chunk keys. Chunk keys are used to decrypt the data.

Where are Pass Phrases stored?

Pass phrases are not stored. Pass phrase must be entered manually by the user for each recovery. However, by creating and exporting a file that contains the scrambled pass-phrase of the client computer to a dedicated directory on another computer, the system can recover the client's data to that (and only that) computer without prompting for the pass-phrase.

Can I restore Pass Phrase protected data using the Command Line Interface?

Yes, by exporting the pass phrase to the target client then use the normal Command Line Interface restore process to recover the data.

Refer to Export an Encryption Pass Phrase for more details.