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The Need For Enc The Need For Encryption ryption

The Need For Enc The Need For Encryption ryption



Susceptibility of unencrypted traffic
Password data sniffing
Data manipulation

Authentication manipulation
Equivalent to mailing on postcards
Insecure traditional protocols
telnet FTP POP3 etc. insecure passwords
sendmail NFS NIS etc. insecure information
rsh rcp etc. insecure authentication
While early networking protocols have provided an indispensable infrastructure,secure authentication and
privacy were often not part of their design As a result,today's networking implementations often provide
inadequate protection for the people who use them.
The mathematical field of number theory has provided cryptographic algorithms protocols and techniques
which provide various forms of networking security,including secure authentication,assurance of data
integrity,and privacy.



 Cryptographic Building Blocks


- Random Number Generator
- One Way Hashes
- Symmetric Algorithms
- Asymmetric(Public Key)Algorithms
- Public Key Infrastructures
- Digital Certificates
- Implementations:

open ssl gpg
Encrypted communication protocols are often assembled from a collection of cryptographic techniques In
a building block fashion A protocol will usually provide a selection of one of several similar algorithms to
fill a particular role For example,public key encryption(used for email and other things uses symmetric
encryption for the bulk of the work A selection of symmetric algorithms such as 3DES CAST5 Blowfish
and others)is available for use in this sort of encryption.
An understanding of these underlying cryptographic building blocks is important to understanding higher
level protocols The various building blocks will be examined in the next few pages,including a discussion
of commonly used algorithms and examples of useful applications.
Red Hat Enterprise Linux (RHEL) ships with two different implementations of cryptographic services

Gnu Privacy Guard or gpg which is used to implement file based encryption ensuring file integrity,
encrypting email messages,etc.
open ssl which provides cryptographic libraries that are used in conjunction with network
communications,such as ssl enabled services and ssh The open ssl command provides a command
line interface to many of the services provided by the openss library.


Random Number Generator

Pseudo Random Numbers and Entropy Sources

keyboard and mouse events

block device interrupts

Kernel provides sources

dev random:
best source
blocks when entropy pool exhausted

dev urandom
draws from entropy pool until depleted

falls back to pseudo random generators


openssl rand [base64]num

Many cryptographic routines rely on random numbers which are notoriously difficult to generate using
computers Generally computers use "pseudo random" random number generators,which are often
seeded with integers In order to improve random number generation,the kernel collects an "entropy pool"
based on user events,such as mouse movements,keyboard hits,and disk I/0 operations. The state of the
entropy pool is maintained in the fivar lib random seed between boots as implemented by the
random service script.
Two character devices allow access to the kernel's random number facilities:
dev random will generate random numbers exclusively from the collected entropy poolIf the entropy
pool is exhausted,the process will block until the pool is replenished the mouse is moved try cat
dev random then move your mous
dev urandom will use the entropy pool until it is exhausted and then resort to a fallback pseudo
random algorithm While reads from dev urandom will not block the random numbers are not
as statistically well formed as those provided by dev random though they are still thought to be
cryptographically strong
The openss library also provides a random number generator accessible through the open ssl rand
comimand open ssl rand also accepts a base64 option which uses base64 encoding to generate printable
ASCII text.

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