Download Apply encryption to network and system security

Reading: Apply encryption to network and system security
Apply encryption to network and
system security
Inside this reading:
What is Encryption?
2
Encryption Methods
3
Authentication
8
Secure Data Transmission
11
Secure Data Storage
14
Threats to Encryption Systems
15
Implementing Encryption Solutions
17
Summary
18
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Reading: Apply encryption to network and system security
What is Encryption?
Encryption is the process of taking some information or data, manipulating
or changing its format in a way that stops it from being used or read by
unauthorized people or systems. Encryption involves scrambling data so
that it needs to be unscrambled, or decrypted, to be read. Encryption can be
applied to data in storage (file systems, media, etc) or in transit via network
or Internet connections.
Encryption can be useful to achieve appropriate levels of network security
required by organisations. For example, an organisation using the Internet
to perform financial transactions will want to ensure that details like bank
account numbers, passwords, etc are kept secure and only accessed by
intended recipients. Encryption can achieve this level of security by
ensuring data confidentiality and integrity.
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Encryption Methods
Information encrypted needs to be decrypted by authorised systems or
people for it to be of any use. To decrypt, the receiver may need some
additional information.
For example you are given a coded message on a piece of paper. To read it
you need to know how it was coded. It may use a simple method of
substituting numbers for letters but to decipher the message you need to
know what letter equates to what number. This is the 'key' that will unlock
the code.
Computer systems encrypt information the same way but use more
sophisticated and complicated codes. Consider the following diagram:
Figure 1: Encryption process
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The encryption process requires the following:

Original information – This is the data or information prior to being
encrypted (may be referred to as plain or clear text)

An algorithm – a mathematical formula or process that accepts the
input of original information and key data to produce an output or
coded information (called cipher text)

Key data – data used by an encryption algorithm to encrypt or
decrypt information

Cipher text – this is the encrypted original information produced by
the encryption algorithm and key data.
The algorithm may work in both directions meaning that information can be
encrypted and decrypted with the correct keys. Knowing any three items
will allow you to derive the fourth. However encryption methods are
designed to make discovering keys and algorithms extremely difficult.
Ciphering
Ciphering is the process of how data or the original information is converted
into cipher text. The process uses algorithms and encryption processes, but
more specifically this refers to how the raw data is managed. There are
generally two cipher methods.

Stream cipher is a relatively simple method where each bit of data
in the original information is sequentially encrypted using one bit of
the key. If the key is of a fixed length it may be possible to
mathematically deduce the key by analysing the cipher text. Using a
variable length key or continually changing the key in the stream
cipher process can theoretically produce an unbreakable encryption
system. One-Time pad is the process of continually varying the
encryption key with random numbers. This method is not
commonly used because of overheads and encrypting efficiency.

Block cipher encrypts the original information into chunks.
Depending upon the encryption system, the size of these chunks or
blocks will be fixed. Each block is processed by an algorithm and
key to produce blocks of cipher text. These cipher text blocks can be
further used with encryption keys to strengthen the encryption.
Block cipher processes more data than stream cipher on each pass
and is more commonly used today.
Private Key Encryption
Private key encryption is also known as symmetric encryption or single
key encryption. This encryption method requires the use of one key to both
encrypt and decrypt information. All people and systems accessing the
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cipher text must use the same key to decipher that was used to encrypt the
data.
Figure 2: Private key encryption
The security of data using this method depends upon the security of the key.
Only authorised people and systems should have the key. It should be kept
private and secret. If anyone else knows the key, the security of the data is
compromised and all data should be encrypted using a new key. The new
key needs to be distributed to all authorised people and systems. This may
present operational difficulties if the locations are geographically diverse,
distant and many.
Examples of private key encryption include:

Advanced Encryption Standard (AES: Rijndael)

International Data Encryption Algorithm (IDEA)

Data Encryption Standard (DES)

Triple Data Encryption Standard (3DES)

HmacSHA1

Blowfish

HmacMD5

TripleDES.
For more information on each of these systems, go online and search for
each term through your preferred search engine (such as Google:
www.google.com).
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Public Key Encryption
Public key encryption, also known as asymmetrical encryption, uses two
keys known as a key pair. One key is a private key and it is kept secret,
only known to one person or system. A second key, known as the public
key, is generated (mathematically derived) from the private key. The public
key is not kept secret and is freely distributed to people or systems that wish
to use encryption.
Figure 3: Public key encryption
Information encrypted with the public key can only be decrypted using the
private key of the key pair. Therefore only the owner of the private key can
decipher the information. The public key used to encrypt will not decrypt
the cipher text it produces. It's a one way process. Public keys are used to
encrypt and private keys are used to decrypt. Information encrypted with the
private key can be decrypted using the public key for authentication
purposes (using 'digital signatures' - this is discussed later).
This encryption method addresses the problem of distributing keys to people
that require them. Public keys do not need to be kept private, so there is no
need for special secure delivery methods and they can be made freely
available using the internet.
Examples of public key encryption systems include:

Diffie-Helman

RSA

ElGamal

Elliptic Curve Encryption.
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For more information on each of these systems, go online and search for
each term through your preferred search engine (such as Google:
www.google.com).
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Authentication
If encrypted information is transmitted or stored, how can we be sure that it
was sent or stored by a specific person? How can we be certain that the
information hasn't been altered, modified or originated from some other
source?
We can use a number of methods to authenticate data and information.
Digital Signatures
Using public key or asymmetrical encryption, information such as
messages, documents, files etc. are encrypted using a public key and
decrypted using the private key of a key pair. The public key is not secret
and freely available so anyone could have encrypted the original data or
information.
The originator can authenticate their data by using their private key. This is
done by using the originator's private key to encrypt information about the
original data (usually checksum information). This encrypted information is
kept with or appended to the original data. This is known as a digital
signature.
This digital signature can only be decrypted using the user's public key. If
decryption of the information (the digital signature) is successful and
compares correctly with that data being accessed (checksum, etc) we can be
reasonably confident of the originator's identity and that the data has not
been modified since the digital signature was added. This is most useful
when downloading data from the internet.
The purpose of digital signatures is to certify information, not conceal it.
Digital Certificates
Public key encryption works using pairs of keys. Anyone wishing to send
an encrypted message must use the recipient's public key to encrypt the
message. If the recipient of the message wishes to verify the digital
signature they must use the sender's public key. Where do we find these
keys and how can we be sure that we are using the correct key of a pair?
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Digital Certificates provide a means of identifying and managing public
keys. A digital certificate is a password protected and encrypted file that
contains information about an individual's identity and their public key.
A certificate server stores digital certificates and is used as a central location
for users requiring public keys. This is known as a Certificate Authority
(CA) and is a trusted authority providing certified public key information.
CA can be setup with in an organisational network or are a service available
on the internet. CAs can work in a hierarchy or mesh fashion to provide
certificates from other CAs.
Reflect: Australian CAs
What Australian organisations act as Certificate Authorities (CAs)? To find
out more, go online and search for the phrase ' Australian Digital Certificate
Authority' through your preferred search engine (such as Google:
www.google.com). You will find large organisations such as Australia Post
and VeriSign Australia act as CAs. What other organisations also act as
CAs?
Public Key Infrastructure (PKI)
Public Key Infrastructure provides a means for users of an insecure network
to exchange data securely and privately. It is a complete infrastructure
using public key encryption to provide the end to end security,
confidentiality and accountability required for information exchange.
Various vendors provide PKI products and solutions.
A public key infrastructure consists of:

A certificate authority (CA) that issues and verifies digital
certificates. A certificate includes the public key or information
about the public key

A registration authority (RA), a network authority that verifies user
requests for a digital certificate and tells the certificate authority
(CA) to issue it.

Locations where the certificates (with their public keys) are held

A certificate management system
For an overview of PKI try the Section 6 networks website
(www.section6.net). Go to the Tutorials section and search for 'Digital
certificates'.
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Reflect: PKI users in Australia
Who is using PKI in Australia? To find out more, go online and search for
the phrase 'Users of PKI Australia' through your preferred search engine
(such as Google: www.google.com).
Kerberos
Kerberos is an authentication protocol that uses secret-key encryption to
verify client identity and exchange information securely.
When a user attempts to logon to a server or system, a local agent sends an
authentication request to the Kerberos server. The server responds by
sending encrypted credentials for the user back to the requesting server or
system. These credentials are then decrypted using the user-supplied
password. If this is successful, the user is issued Kerberos authentication
tickets and a set of cipher keys to encrypt data sessions.
Kerberos is a cross platform system developed by Massachusetts Institute of
Technology (MIT) and has been incorporated into numerous products by
vendors. See the website: web.mit.edu/kerberos/
Reflect: Kerberos
Find out more about who uses Kerberos. Use your preferred search engine
(for example Google: www.google.com.au) to search for information about
which products use Kerebos. Does Windows use it? What about Eudora or
SAP?
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Secure Data Transmission
There are a number of methods that use encryption to ensure that data
transmission on a network is secure.
Internet Protocol Security (IPSec)
This protocol defines encryption, authentication and key management for
TCP/IP transmissions. It secures data in transmission by various means at
the IP packets level.
The key components of IPSec are:

Authentication Header (AH) This component authenticates and
validates data packets. Each packet basically contains a digital
signature

Encapsulation Security Payload (ESP) This component encrypts the
data payload of the packet.

Internet Key Exchange (IKE) The above components AH and ESP
use asymmetric encryption. IKE manages the public/private key
exchanges for encryption and decryption.
IPSec can operate in two modes:

'Transport' mode encrypts communications between two hosts.

'Tunnel' mode places an encrypted IP packet into a traditional IP
packet to ‘tunnel through' to a destination. This is used to support
VPN transmissions.
For more information, go online and search for the term 'IPSec' through
your preferred search engine (such as Google: www.google.com). You
could also try the NetBSD project website (www.netbsd.org - enter 'IPSec'
in the search tool and find the 'IPSec FAQ' document).
Point-to-Point Tunnelling Protocol (PPTP)
The original Point-to-Point Protocol (PPP) is an encapsulation protocol for
transporting IP traffic over point-to-point connections.
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The Point-to-point Tunnelling Protocol (PPTP) is an expansion of the
existing Point-to-Point Protocol (PPP). PPTP uses the same principle of
encapsulating other protocol packets so that they can be transported via a
switched network (the Internet) to a specific destination. The destination
receives the PPTP packet and extracts the encapsulated data. PPTP also
supports encryption and authentication.
This protocol is a proprietary Microsoft development and is widely used in
conjunction with VPN (see below). There are open source alternatives that
will also work with PPTP (for example 'PPTP Client' - see the Sourceforge
website: pptpclient.sourceforge.net).
Layer 2 Tunnelling Protocol (L2TP)
This protocol is similar to PPTP but developed by a number of industry
consortia. This protocol has become the method of choice for Microsoft
Windows VPN
L2TP is just a tunnelling protocol. It is generally used with IPSec to
provide encryption.
Virtual Private Network (VPN)
Virtual Private Networks are basically a secure connection through a
network (Internet, WAN, etc) that connects either computers or networks
together. These connections make remote users appear that they are on one
single network.
The main functions provided by VPNs are tunneling, data security, data
integrity and authentication. This is usually provided by a number of
protocols, IPSec, PPTP and L2TP.
Secure Sockets Layer (SSL)
This is a method of encrypting TCP/IP transmissions between hosts. It is
used for the encrypt web pages and data on web forms reroute. The
encryption method uses public key encryption. It requires Digital
Certificates
URLs prefixed with 'HTTPS' initiate an SSL session between the web
browser and web server. Most online banking facilities will direct you to a
secure site with 'HTTPS' at the beginning of the address.
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Secure Shell (SSH)
This provides a secure means of establishing remote connections to a host.
It provides authentication via the exchange of digital certificates and uses
public key encryption. It is mainly used in Unix/Linux environment and is a
means of using insecure protocols (telnet, ftp, etc) in a secure fashion.
Pretty Good Privacy (PGP)
This is one of the most popular encryption programs. This is a public key
encryption system that provides authentication and encryption. It is
commonly used for email transmissions and supports a wide range of
operating systems. Both commercial and open source versions are
available.
See the website: www.pgp.com for PGP information.
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Secure Data Storage
Encryption may be used to protect the confidentiality, integrity and
authenticity of data in storage, such as that on a hard disk drive or tape.
Encryption methods as discussed previously may be used but careful
consideration must be given to the consequence of this.
Encrypting and decrypting data creates a significant overhead in terms of
time and effort and will affect the accessibility and management of the data.
There may be key management issues – numerous key pairs required, digital
signatures and CA (certificate authority) required. Implementation will be
determined by the business or organisation needs and requirements.
Most operating systems and storage systems have inbuilt encryption
facilities. Implementing these may be more efficient but does place a
reliance on the operating system.
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Threats to Encryption Systems
The security that an encryption provides may be vulnerable because of
possible deficiencies or circumstances.
Deficiencies in human and business processes or
procedures
No matter how good an encryption system is it still requires some sort of
management. Security relies on keeping private keys secret. If keys are
stored or delivered ad hoc there is a good chance that the private keys will
be compromised. Management and maintenance processes need to be
checked to ensure security.
Users need to be aware of security issues. For example an encryption
system may be doing its job well, but if a user leaves a logged on computer
unattended the confidentiality of information may be compromised by
someone else accessing the logged on computer.
Deficiencies in the cipher algorithm or process
Original data may be deciphered from cipher text by exploiting some
weakness in the cipher algorithm. Algorithms that are publicly known, have
been available for some period of time and have had public scrutiny have
generally proved their security. Systems that are new or rely on secrecy are
possibly vulnerable.
Brute force attacks against the key
This is where attempts are made to gain the original text from the cipher text
by using every possible combination of the key or password. The longer a
key is (i.e. the more bits used in encryption) the more possible combinations
there are. The larger the number of keys used to create the cipher text the
more number of keys need to be tried.
Brute force attacks will eventually succeed if enough time and resources are
used. For example, it took 312 hours using 3,500 computers to find a RC5
key. (RC5 is a block cipher method that uses 64bit symmetric keys) A key
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is considered strong if the cost of finding the key outweighs the cost of the
data being protected.
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Implementing Encryption Solutions
Encryption systems can be provided by network operating systems and
devices or by third party products and services.
Inbuilt encryption systems provided by operating systems and devices may
be cost effective. However if these are propriety systems, using them may
lock the organisation into a significant dependence on the operating system
or device.
Third party encryption solutions are usually built on industry standards and
generally operate independent of any operating system or devices. These
solutions can be expensive.
In all cases, any implementation of encryption solutions will be governed by
the security requirements for an organisation or process. The benefits of
encryption need to be weighed against the real threats to data security,
implementation requirements and costs.
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Summary
Investigating and implementing encryption facilities and the appropriateness
of this for organisational network security requires a sound understanding of
encryption methods, practices and standards. We have covered the main
components – symmetrical and asymmetrical encryption, digital signatures,
and digital certificates. Secure transmission methods such as SSL, VPN,
and IPSec have also been discussed.
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