NLS Backup

Frequently Asked Questions Regarding Data Integrity

5 Questions to ask your Online Backup Provider

Introduction

Competition is fierce in the exploding online backup industry. With so many providers, whom can you trust with your company’s data? As a managed service provider, NLS Backup employs solutions that will get your data back when you need it. There are fewer issues that are more sensitive than lost or corrupt data.

Finding a place to backup data is relatively easy these days, but discerning which provider can restore the verifiably correct data all the time every time is much more difficult. This tutorial is intended to help you discover the empirical facts you need to determine whether or not to entrust your data with an online backup provider.

Q1) Which established standards do you follow for your cryptography?

In the complex world of cryptography, following well-established standards is the only sure path to safety. An excellent example is the proprietary GSM A5/1 cell phone encryption algorithm, which was subsequently broken. Another risk is that even if the encryption algorithm itself is standardized (such as AES), if the use of that algorithm (called cipher mode) does not follow standards, it is subject to serious flaws. For example, one provider used AES in CTR mode, but chose to deviate from the NIST 800-38A standard and re-used the IV, causing their solution to become vulnerable to known-plaintext attacks. Ask about standards with respect to the following: encryption, hashing, and MAC algorithms, cipher modes, and pass phrase key generation.

Q2) Is your cryptography implementation well-known and open-source?

Cryptography is hard to implement correctly and securely, especially if it needs to be fast. Improper implementations are vulnerable to timing attacks. Bugs can also cause data corruption. Another danger is the presence of “back-doors” in an implementation that would allow access to the data without the encryption key – if a provider is using an established open-source cryptography library, the community has scrutinized the source code to make sure that it is correct, secure, and fast.

Q3) Which cryptographic primitives are used to protect the integrity of the data?

Many providers focus so much on using cryptography to protect the confidentiality of your data that they fail to consider another important aspect – data integrity. Encryption only provides secrecy but not data integrity. This is why cryptographic message authentication codes must be used in addition to encryption. A Message Authentication Code provides a cryptographic fingerprint that detects malicious tampering and accidental or silent data corruption. Ask which Message Authentication Code algorithm is used, whether Message Authentication Code fingerprints are stored on disk, and whether the fingerprints are verified upon restore.

Q4) Which mechanisms and processes are used to protect against silent-data corruption?

Silent data corruption is caused by physical failures, corrupted or buggy firmware, misdirected writes, driver bugs, file system bugs, and human error. A recent study by CERN found that in a sample size of 8.7TB with 33700 files, 1 in 1500 files had some corruption, with an overall bit error ratio (BER) of 1^10^-7. Any hardware-only solution, including RAID, will not provide end-to-end coverage of all issues. Ask what technology is used to detect and repair silent data corruption, length of block checksums, where those checksums are verified and repaired, how much data redundancy is employed for repair, and whether the cipher mode is sensitive to single-bit errors. Be wary of providers that say integrity is provided through mirrored data centers without mechanisms specifically for silent data corruption – without detection mechanisms any data corruption will be silently mirrored to the other data center as well.

Q5) How often is the integrity of actively changing and archived data actively verified?

Frequently verifying data integrity mitigates risk through early detection and repair. Also, while systems should have a defense-in-depth solution so that silent data corruption never occurs, responsible solutions will have an open reporting policy, which is especially important for regulatory compliance. Ask how often the integrity of actively changing is verified, how often the integrity of archived data (historical and non-changing data) is verified, and who is notified if corruption ever occurs.

Conclusion No matter who you choose for online backup, make sure it’s one that provides the highest level of data integrity protection. Refusal of a provider to disclose high-level information because of “security concerns” is in opposition to a well-known principle in cryptography called Kerckhoff’s Law, and may be a sign of insecure design choices or a lack of confidence in the security of the cryptographic primitives employed by their solution.

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