Security_Data_at_rest

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Securing data-at-rest In the early days of computing technology, computerswere mainly used for mathematical computations andthe associated permanent storage media was verylimited in capacity and directly attached to thecomputers. Also data accessibility was only for limitednumber of users. Hence, the threat to data security wasnot high. These days, computer technology has

matured and is providing superior processing power,huge storage support and facilitating anywherenetworking while the data storage demand isincreasing exponentially. Today users spread acrossgeographies are provided access to data storagedevices which has popularized the use of NAS (NetworkAttached Storage) and SAN (Storage Area Network)technologies. Sensitive data traveling throughworldwide networks or stored in devices within this

network is at a risk of falling in wrong hands especiallywhen the data is resting on storage media and devices.

This paper describes about security threat to the data-in-motion and data-at-rest, mainly focusing onencrypting the data when it is in rest. It covers basicelements on the topic of storage security, storagesecurity model and various data encrypt ion algorithms.


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Securing data-at-rest

About the Author

Suraj Kumar Bhatnagar

Suraj Kumar Bhatnagar has been working with TCS since2001 and currently, he is a part of Storage COE, High-TechPractice. He holds a Bachelors degree in ComputerEngineering from G. B. Pant University of Agriculture andTechnology and a Masters degree in Computer Science andTechnology from Indian Institute of Technology, Kanpur.

Suraj has worked on Systems Software designing anddevelopment in the Storage Technology with several

engagements with TCS. His area of expertise is NAS, CIFS,NFS, File Systems and Protocol Stacks development in thearea of IP and ATM networks.


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Table of Cont ents1. Introduction 3

2. The Need For Data Security 33. Securing Data 4

4. Layering Data Security 5

5. Some encryption algorithms 8

6. Conclusion 9

7. References 10



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Introduction

The Need For Data Security

Data storage has come a long way since the days of early computers. The volume of data in the early days ofcomputers was negligible as compared to today. Back then, a few disks or tapes were sufficient to store the data.Since most computers were standalone and only the users had access to data, security was not a big concern.All this changed when computers became linked in networks, what started with small dedicated networks soontook the form of large LANs, WANs and the World Wide Web. With the rapid growth of networking came thevoluminous increase in the data flow. In this scenario, the security of data became a big issue. Storage technologieslike NAS, NAS, FAN, IP SAN, and Virtualization have made data accessible to thousands of users across the worldwithout their knowing where the data is physically stored. Data passes through various networks, communicationprotocols, and devices to ultimately reach to the user. This has led to a concern regarding security and data securityhas become increasingly important. For companies that earn their livelihood from data management, protecting itis of paramount importance. Data security faces threat in two scenarios when it is in motion, being t ransferred or atrest.

Data-in-motionThe various standards are used to secure the data-in-motion like SSL (Secure Sockets Layer), TLS (Transport LayerSecurity), and IPSEC (Secure Internet Protocol) using a combination of RSA, RC4, DES, or Diffie-Hellman algorithm.

Data-at-restThe data-at-rest can be made secured by providing two level of security: controlling the access to the data by Accesscontrol and Encryption.

The yardstick of measuring everything in todays business world is revenue. With large corporate relying on storagenetwork for safekeeping their valuable data, lack of security makes the storage network environment unreliable,unstable, and unavailable which ultimately leads to the loss of revenue. Storage networks must be made reliableand stable in order to support business operations. Devices that depend on storage system elements, such asdatabases, Web servers and email servers require a stable environment. Securit y measures will increase the stabilityof an environment by ensuring that the network components that make up the storage environment are able tocontinue to perform in both normal and abnormal conditions.

Availability is the first and foremost issue in support ing a business. Downtime can equate to loss of revenue and/orloss of production. By making the storage more secure, companies can reduce potential downtime due tounauthorized access attempts, malicious code, and other issues.

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Securing Data

The best way of securing the data is to restrict access to the data. This is best achieved by the process ofauthentication and authorization. A user should be asked for authenticating information before accessing the dataand should only be allowed to perform the operations for which access rights are available.If the data to be accessed is on a local machine, applying access control is easy. It is taken care of by the file-system ofthe local machine, but if data is accessed from a remote client using protocols like NFS, CIFS, HTTP, or FTP, usercredentials and data needs to be secured on the network. It is in such cases that security protocols like SSL (SecureSockets Layer), TLS (Transport Layer Security), and IPSEC (Secure Internet Protocol) are used.In the event that a malicious user somehow breaches the above security provisions and gets access to data, thesolution is scrambling the data. So encrypting the data whether it is in-motion or at-rest is the next level ofsecurity that will make the data worthless for the hacker.

Access cont rol

Access control is achieved by the means of Authentication and Authorization.Authentication is used to verify the identity of an entity and Authorization is used to determine which rights to grantto an authenticated entity.

EncryptionEncryption is used to scramble the data, which can only be accessed through appropriate credentials/keys.Encryption can be categorized into two types encryption of data-at-rest and encryption of data-in-motion.

Encrypt ing data-in-motion Encrypt ing data-in-mot ion hides information as data moves across the network. From the storage to the servers

or back. This type of encrypt ion has several standards such as Secure Sockets Layer (SSL), Transport Layer Security(TLS), and Secure Internet Protocol (IPSEC). Most database vendors have adopted the SSL standard, and include theability to send t raffic between the client and database vendor over an SSL tunnel using some combination of RSA,RC4, DES, or Diffie-Hellman algorithm.

Encryption of data-at-rest Encrypt ing data-at-rest secures the information stored in the database. Encrypt ing data-in-mot ion does nothingto protect data that is att acked at the end points. It is a fact that most attacks occur against the end points of data,where data sits for long periods of time rather than on data-in-motion. Considering this, we find ourselves in anuncomfortable situation wherein encryption of data-in-motion is already widely adopted but even the most

security-conscious database administrators have not adopted encryption of data-at-rest.The aim of encrypting the data-at-rest is to protect t he data when it is resting in the form of files in the file systems,database tables in t he database or a raw data in blocks in the SAN environment.Data security layers in the next section explain encryption of the data by an application at application layer,encrypting the files or databases tables at file/record layer and encrypt ing blocks at block layer.


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Layering Data Security

Securing the data-at-rest by encrypt ion involves encrypting it at various levels. This section explains the encryptionat application, file/record and block layer.

Applicat ion-based encrypt ionIn this type of encryption, data, like files and directories, is individually encrypted at t he discretion of the end user. Aseparate suite of applications can be developed to encrypt and decrypt data as and when required by the user.

Although such software affords a high degree of flexibility in choosing the exact files to be encrypted, the process isnon-transparent and cumbersome. The init iative and decision to encrypt data as well as key management is left withthe end user. Application based measures can require extensive coding changes, create inconsistencies acrosssystems, and produce ongoing maintenance headaches.

File/Record based encryption

Encrypt ing at File System level Managing cryptography at the file subsystem layer of the operating system brings several advantages such astransparency to users and applications, flexibility of key management and access control, good performance, andimmunity from an array of attacks. Separate keys may be used to protect different file system objects that may beshared with other users on an individual basis. Some encrypt ing file systems are given below.

Cryptographic File System (CFS)The CFS was the first encrypting file-system for UNIX. It is implemented as an NFS server that introduces acryptographic layer between the virtual file system and the disk. The end user is required to manually attach anencrypted volume before using it to read or write files. Key management in the Cryptographic File System is fairlybasic and uses a common pass phrase-derived mount-wide key.

Figure 1: Layering Data Security

ApplicationLayer

File / RecordLayer

BlockLayer

Application-basedEncryption

File / Record-basedEncryption

Application

File / Record

Database File System

Block Aggregation

Host

Network

Device

Host-based

Appliance-based

Device-based

Block-based Encryption


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Windows Encrypt ing File SystemMicrosoft Windows provides a native Windows Encrypt ing File System that is tightly integrated with the NTFS filesystem. It s key management scheme uses different keys for different files and associates a public and private key pairwith all users. This enables finer access control and provides greater flexibility to end users when sharing protecteddata.

Dm-cryptThe most popular encrypting file system for Linux is dm-crypt. The native kernel CryptoAPI provides the encrypt ionand decryption rout ines. It is a very performance efficient implementation and part of t he standard Linux kernel.However, it lacks flexibility due to the use of a common mount-wide key and tackles a narrow threat model. Hence,sharing specific files with specific users in large organizations is an issue that is left unresolved by dm-crypt. Thislimitation makes dm-crypt suitable for most personal applications but not for enterprise deployment.

eCryptfs

eCryptfs is the first attempt at designing an enterprise-class cryptographic file system for Linux. It provides anadvanced key management scheme using per-file keys and user-specific keys.

Encrypting at database level Encrypt ing data at file system level provides the encrypt ion to the files and folders. Database maintains the tables ontop of file systems in terms of files, and relies on file systems for encrypting those files. There are many weaknesses tousing this strategy. You cannot selectively encrypt individual pieces of data. This approach result s in encrypting theentire file, which means all the data is encrypted. This causes serious performance problems for reading from thedatabase. Every time data is read from the database, it is encrypted whether or not the data really needs to besecured. This adds significant overhead to any action performed against the database.

Another weakness of encryption at file system level is that different pieces of data cannot be encrypted withdifferent keys. Imagine you have a database which is shared by two or more different departments within anorganization. One department needs to access the columns which are restricted to other department and anotherdepartment needs access to the columns which are restricted to first one. This cannot be achieved using file-levelencryption, because operating system file encryption encrypts the entire file, not sections of the file.

So the data in the tables can be encrypted at column-based and a key can be attached with each column providingsecurity to the section of the tables if multiple departments are using the same table in the database. Moreover,requirements for applying encryption on columns can be analyzed and encryption can be applied only to the

columns having sensitive data. For example, a table having customers record like customer ID, name, address, andcustomer credit card number has sensit ive information in the last column i.e. credit card, so only the column havingcredit card information should be encrypted for the better read performance.

Block-based encrypt ionIn the SAN environment, storage can be virtualized at host, network and device level. The blocks provided by storageappliances in t erms of LUN/logical disk can be used by the host to create a volume group and logical volumes, orstorage can be used by the switch in between to aggregate the blocks from various storage appliances or by storageappliance itself can have control on blocks provided by it.Data at block level can be encrypted by the host when it is created, when it s being t ransported across the networkby the appliance attached to the switch, or when it s with storage device. Each of these methods has advantages anddisadvantages. Heres a brief overview.


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Host-based encrypt ion With host-based or server-based encryption, data is encrypted the moment its created, providing the highestpossible level of data security. Since data is encrypted at creation, theres no chance of unencrypted data beingintercepted. If data is intercepted, encryption renders it unreadable and worthless. Host-based encryption is highlysecure and well-suited to active data files. Its implementation requires change in current operating infrastructures.Moreover, encrypted data can not be compressed at storage end. The main drawback of this approach is the need ofaddit ional computation power at host-end to encrypt and decrypt the data. Another drawback is to the overall costdue to regular maintenance of encryption software at host-end.

Appliance-based encrypt ionIn appliance-based encryption, data is encrypted while being t ransported from the creation point to its destination.This method protects data at the network level, implementing security features on LAN-connected or SAN-connected encrypt ion appliances or switches.Data leaves the host unencrypted, and then goes into a dedicated appliance where it is encrypted. After encrypt ion,it enters the LAN or a storage device. Although it is a costly opt ion, requiring a dedicated appliance for every two tosix storage devices, it is simple to install and requires no changes to the existing data infrastructure. Moreover, it isthe least scalable of the three methods. It works well as an immediate fix, but it grows more expensive and is more

difficult to manage as data volume increases. It is easy to implement and it is well suited as a quick method forlocalized encryption solutions.

Device-based encrypt ionData can be encrypted on a disk controller or dedicated storage server making it easy to validate and at the sametime eliminating the performance penalty on the server. This method is easy to implement. Its a good fit for mixedenvironments with a variety of operating systems. Device-based encryption supports data compression. Since thestorage devices handle the encrypt ion t ask, no changes are required to the existing data infrastructure. Decrypt ioncode is built into the data storage container, so theres no need to maintain decryption software specifically forarchived data.Even though it is easy to implement and cost-effective, best suited to static and archived data, it is not very secure asthe data is transmit ted unencrypted till it reaches the storage device. Moreover, existing storage devices need to bereplaced to support the technology.

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Host-basedEncrytion

Host Server

Encrytion Appliance SwitchAppliance-basedEncryption

Device-basedEncryption

Disk Array Tape Library

Figure 2: Block-based encryption


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Some encrypt ion algorithmsSome encryption algorithms are explained below.

DESThis algorithm was developed by IBM for protecting computer data against possible theft or unauthorized access.DES is now considered to be insecure for many applications; this is mainly due to the 56-bit key size being too small.

TripleDESThis algorithm is a variation of DES. It takes a 192 bit key (24 characters) as input and breaks it into three keys. First,DES is used to encrypt a file using the first key, then the file is decrypted using the second key and finally, DES is usedto encrypt the file again using the third key.

SkipjackThis algorithm was developed by the U.S. National Security Agency (NSA). It uses an 80-bit key to encrypt or decrypt

64-bit data blocks and was designed for replacing DES. It has been extensively cryptanalyzed, and has noweaknesses.

BlowfishThis algorithm was designed in 1993 by Bruce Schneier. It uses a variable-length key, from 32 bits to 448 bits and afast, free alternative to existing algorithms like DES.

RijndaelThis algorithm was designed by Joan Daemen and Vincent Rijmen and was selected for the Advanced Encrypt ionStandard (AES). It is highly secure and has undergone extensive cryptanalysis.

oTwofishThis algorithm is Counterpane Systems candidate for the AES. It is a symmetric key block cipher with a block size of128 bits and key sizes up to 256 bits. It is designed to be highly secure and highly flexible.

oMARSThis algorithm was designed by IBM as a candidate for the AES. It uses a 128-bit block size and a variable key size ofbetween 128 and 448 bits.

Serpent

This algorithm was designed by Ross Anderson, Eli Biham and Lars Knudsen and was the candidate for the AES. Itsupports a key size of 128, 192 or 256 bit s.

RC6This algorithm was designed by RSA Security and was the candidate for the AES. It uses a block size of 128 bit s andsupports key sizes of 128, 192 and 256 bits.


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Conclusion

Understanding the need to secure your data is the first step towards securing it. In todays age every detail personalto corporate secrets is present in form of data. For computers and networks which store and transfer this data, it is

just numbers. It is for us to realize the damage this data can do if it falls into the hands of an unscrupulous person.Whether the data is on your laptop, desktop, or on an organizations storage network, it must be secured and shouldnot come in the hand of an unauthorized entity.

Proper access control mechanism should be enforced for securing the data. While in mot ion, data should be wellprotected. It is advisable to encrypt the data before putting it on a network even if it passes through a securechannel.

Data lying on laptop, desktop, and NAS appliances can be encrypted at file as well as block level. However,encrypting the data at file system level provides robust security. Encryption of the file is done on per file key and

users unique private key. Data in the form database should be encrypted at column level. Encrypt ing all columns inthe database table is not advisable as it decreases the performance. NAS appliance represents the disk space to usersin terms of the file systems and can support the encryption at file system level.If encryption at file system level can not be achieved, it is worth encrypting the data at block level before writing todisk. This can be done by Volume Manager or RAID Cont roller.

In SAN environment, data can be encrypted at source from where it is created, by a dedicated appliance betweensource server and storage appliance, or by a storage appliance at block level. If storage is virtualized at switch level, itis advisable to encrypt the data by a dedicated appliance attached to switch. If virtualization is provided at storagelevel, SAN appliance itself or a dedicated encryption appliance before SAN appliance can be used for encrypting the

data.

Most import ant place where data needs to be encrypted is backup appliance and backup media. It can be virtual orphysical tape library. If data is not encrypted at application level or file system level coming to the tape libraryunencrypted, it should be encrypted before writing to virtual or physical tapes. It is most vulnerable place for theft asdata rests there for long periods of time.

Organizations having sensitive data must encrypt it at all levels of it s lifecycle whether it is on production server atapplication, file system and database layer, or at storage layer which includes primary, secondary and tertiarystorage. Organizations need to carefully choose the specific place to encrypt the data on the basis of where sensitive

data is managed or used.


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References1. Anthony Harrington, Christian D. Jensen- Cryptographic Access Control in a Distributed File System 2.Matt

Blaze-A Cryptographic File System for Unix3. Roman Pletka, Christian Cachin-Cryptographic Security for a High-Performance Distributed File System

20064. Kelvin F, M. Frans Kaashoek and David Mazieres- Fast and secure distributed read-only file system5. Scott A. Banachowski, Zachary N. J. Peterson, Ethan L. Miller and Scott A. Brandt- Intra-file Security for a

Distributed File System6. Benjamin C. Reed, Mark A. Smith, Dejan Diklic- Security Considerations When Designing a Distributed File

System Using Object Storage Devices7. SNIA-Encryption of Data At-rest, Step-by-step Checklist8. Introduction to Storage Security, A SNIA Security White Paper


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