IDC NetVista User manual

WHITE PAPER
The Coming of Age of Client Security: Top Managers Realize They
Have to Lock Down the Point of Entry
Sponsored by: IBM Corporation
Roger L. Kay
January 2003
SUMMARY
Although security technology has progressed tremendously over time, awareness of
the need for security on the part of people who use computers — both consumers
and businesspeople — has not in general kept pace. Essentially, there is plenty of
technology on hand, but the understanding of what it does and how to use it has
lagged. However, much has changed since the attacks of September 11. CEOs and
IT managers everywhere drew lessons from the differing fates of companies that had
backup and restore procedures and those that didn't. Data recovery is, of course, only
one piece of the security pie, but as political tensions have increased on the macro
level, this and other security concerns have risen in visibility with top managers. "To
what degree is our data — and therefore our business — safe?" CEOs are now
asking in ever greater numbers and with increasing vehemence. "Just where are we
with security?" they want to know of their CIOs.
This shift in attitude represents an evolution from the pre–September 11 state, which
was characterized by a vague awareness of some subset of security issues but a
misunderstanding of the complete security picture and a widespread lack of adoption
and deployment.
Now managers are beginning to assess their vulnerability and to ask what their
alternatives are.
In most corporations, the security infrastructure is still inadequate and full of holes.
Even the most sophisticated organizations are vulnerable. In one incident, widely
reported in the press, that had an impact of major but unknown proportions — the
degree of penetration was difficult to assess — a hacker from St. Petersburg, the
intellectual seat of the old Soviet Union, broke into Microsoft's network and
absconded with a large number of important files, including, purportedly, an unknown
quantity of Windows source code files. Naturally, Microsoft never advertised the
extent of the damage — if, indeed, it is actually known. And if a company at the
epicenter of the information technology business is vulnerable (and by inference
should know better), truly, no company is safe from attack.
The security threat is growing in several dimensions at once. The amount of value
flowing across the network — in the form of actual money, but also business plans,
intellectual property, and strategic documents — is rising by leaps and bounds. And
value is at risk in less obvious ways. A reputation can be damaged irreparably by an
attack, business can be lost as a result of downtime, and the trust on which ebusiness
is based can be destroyed permanently. To the growing list of imaginative crimes
must be added identity theft, which has become a veritable cottage industry. In
addition, malicious hackers are getting more sophisticated. Malevolent programmers
are not only figuring out more effective ways to harm businesses and individuals but
are also publishing their tricks on Web sites for other less creative, but perhaps more
vindictive, people to find and use.
Global Headquarters: 5 Speen Street Framingham, MA 01701 USA P.508.872.8200 F.508.935.4015 www.idc.com
“To what degree
is our data 
and therefore our
business safe?"
CEOs are now
asking.
The security threat
is growing in several
dimensions at once.

2 #3577 ©2003 IDC
In this environment, client security can be one of the weakest links in the chain.
Despite the availability of operating systems with improved security features, desktop
and notebook PCs still often have only a Windows password protecting them, and, in
older Windows versions, these flimsy mechanisms are easy to crack. Once inside the
organization by way of an unprotected node, a malicious hacker has the run of the
place to the extent that the legitimate user of the system did. From this position, the
intruder can execute transactions as if he were the victim. And worse, in this era of
the Internet, the perpetrator does not even have to be physically onsite, but can reach
the system remotely. And if the hacker is sufficiently sophisticated, he may be able to
get at the most sensitive areas of the network, pillaging information, destroying
functionality, or even potentially turning computer after computer into a rogue slave
that does his bidding. Even if other security measures — such as physical access
control, firewalls, network security, software security, database encryption, and
server-level intrusion detection — have been instituted, the client node may indeed
represent a weak point in the corporation's armor.
Although the mathematics of security are theoretically solid, a secure implementation
depends on both the embodiment of the algorithms and the procedures for handling
sensitive data and the keys used for encryption and decryption. Although modern
encryption is virtually uncrackable, encryption implemented in software is an open
door to hackers. In software encryption, various ways exist to sniff the most important
element — the user's private key. To address this weakness, IBM has embedded the
entire process in hardware. An industry group composed of all the major
manufacturers and suppliers and many smaller ones has agreed to drive the standard
into the marketplace. The Trusted Computing Platform Alliance (TCPA to its friends)
is now in the second revision of the standard, and this revision is expected to be
incorporated into Microsoft's Palladium security infrastructure, due to hit the market in
2004 or 2005. Although IBM acted unilaterally to design and implement its hardware
solution, key players in the industry have acknowledged the design point. The TCPA
was inaugurated with IBM, Hewlett-Packard, Compaq, Intel, and Microsoft as
founding members. Since, its inception in October 1999, more than 190 firms have
signed up, including Dell. TCPA wants its security technology to be universal in the
computing industry, and IBM has committed to making it available via license to
anyone who wants one.
IBM itself has moved on from the original embodiment of the TCPA standard, a
security chip or cryptographic microprocessor that was soldered onto the system
board of the client and connected to the main processor by a local bus, and now
offers an implementation as a modular daughter card. There is no way a Trojan horse
can sniff the chip on the card because all private key operations take place within a
protected hardware environment. Since its key-management structure is hierarchical,
a single private key can be used to secure a large number of certificates (issued, for
example, by diverse entities such as a senior citizens group, a corporate employer,
Microsoft Outlook, American Express, and MasterCard).
The hardware is designed to work with a suite of other security elements, such as
firewalls, antivirus software, security policy software, and Internet Protocol Security
(IPSec), to provide a complete security solution. In addition to being extremely
secure, the hardware is simple to use and inexpensive.
In an ebusiness world, trust, protection of privacy, and a secure operating
environment are essential. The benefits of hardware-based security are obvious:
Private keys are truly safe from malicious hackers, multiple secure keys can be
generated to facilitate ecommerce with a wide variety of entities, and, combined with
a full security suite, hardware encryption enables another layer of security, making
ebusiness more viable. The simple conclusion is this: If your client-level security isn't
implemented in hardware, your systems are more vulnerable.
In this environment,
client security can be
one of the weakest
links in the chain.
A
lthough modern
encryption is
virtually uncrackable,
encryption
implemented in
software is an open
door to hackers.
The simple conclusion
is this: If your client-
level security isn't
implemented in
hardware, your
systems are more
vulnerable.

©2003 IDC #3577 3
The Microsoft intrusion was a so-called "lunchtime attack," named for the archetypical
scenario in which an employee goes out to lunch, leaving his or her computer on, and
an intruder simply sits down at the absent worker's desk to feast on whatever
privileges that user enjoys, including access to files, programs, and services.
Without having to resort to social engineering, a lunchtime attack can be thwarted
quite easily by a variety of authentication methods based on client-level hardware
encryption. For example, the operating system can be set to lock out access after a
short period of time if it receives no further input and be reactivated only via biometric
recognition or a proximity badge, or both, eliminating the need for passwords, which
can be forgotten or stolen. If the network had been able to interrogate the remote
client to find out whether or not it was authorized, Microsoft would likely have been
able to prevent the attack. Had appropriate fail-safes been in place, the hack would
likely not have been successful.
The need for stronger security is well demonstrated, and effective measures to
protect data and users exist in the marketplace today. We're not talking about
something two or three years down the road. IT managers should look into these
technologies now.
THE SECURITY LANDSCAPE
In this paper, we will cover a number security-related topics, including:
! Business managers' growing consciousness of security issues
! How the PC client can be the weak point in the security perimeter
! The rise in the value of data stored in insecure computing systems
! The scope of security measures
! Security history and current technology
! Client security implementations
! The advantages of IBM's hardware security implementation
! The evolution of industry standards for client security
USAGE LAGS BEHIND TECHNOLOGY
Security technology has come a long way since the day in 1586 when Thomas
Phellips, Queen Elizabeth's decipherer, broke Mary Queen of Scots' simple offset
code, an unfortunate event that led directly to Mary's trial and execution. Today, a
malicious hacker trying to break so-called "Triple DES" encoding with all the
computing power currently hooked up to the Internet simultaneously would need 64
quadrillion years to do the job, plenty of time to slip back over the border into
Scotland. And Triple DES is by no means the strongest code out there.
But usage of security measures in the data world has not tracked the technology
itself. People just haven't gotten the message that security is important. For example,
denial-of-service attacks involve the penetration and hijacking of innocent people's
PCs unbeknownst to them and then unleashing the enslaved systems' power
simultaneously in a stream of requests that block legitimate traffic to targeted servers.
These attacks first surfaced in 1999, but the average user still hangs out on the
Internet with unencrypted connections, vulnerable to getting picked off by a sniffer,
A
denial-of-service
attack on the
Internet's 13 root
servers successfully
crippled traffic on the
Internet as recently
as October 2002.

4 #3577 ©2003 IDC
and a denial-of-service attack on the Internet's 13 root servers successfully crippled
traffic on the Internet as recently as October 2002. This attack has been connected to
cyberterror, and IDC is expecting at least one major cyberterror attack on the Internet
infrastructure in the not-too-distant future.
In addition, as wireless installations, home networks, and hotspots become more
common, the opportunities for client penetration are only increasing. Many users don't
even turn on the encryption available on their wireless connections. Picking traffic out
of the air is commonplace, albeit mostly harmless. Nonetheless, on occasion, the
crown jewels are exposed.
Of course, awareness and concern about security issues have risen among corporate
executives since September 11, but a steady drumbeat of increasing Internet fraud
and identity theft has been rising in the background as well. The multiple directions
from which cyberdanger can come are among the main worries of IT managers.
Access control and authentication are key for enterprises with remote employees.
Physical security remains a hot topic, particularly as devices are becoming smaller
and more mobile.
Although IDC surveys show that IT executives in companies engaged in ebusiness
activity have always led others with respect to security, awareness and
implementation are beginning to become more mainstream for enterprise networks.
Security has moved from the global realm of total systems, such as the public key
infrastructure (PKI), which require cooperation and trust among multiple entities, and
focused on the more immediate task of authenticating users at the point of entry and
encrypting local files.
While at the highest level most of the attention to security is focused on protecting the
information of greatest value to the corporation — financial, personnel, and
proprietary technical data — whether it lies in the mainframe, on the network, or in
clients, at the low level of client protection most of the focus has shifted to ensuring
that the cordon sanitaire is unbroken at the access point and that user files are
secured. Good mainframe security implementations, particularly at the procedural
level, have been in place for a long time. Network security, which makes use of
techniques such as intrusion detection and firewalls, is primarily concerned with
availability and integrity. Client security is now extending from antivirus products and
limited password controls to robust authentication methods and protection of
intellectual property.
THE IMPORTANCE OF THE CLIENT TO OVERALL
SECURITY INFRASTRUCTURE
Security in a networked environment is achieved by deployment of a full set of
protective measures. These measures include software-based perimeter defenses
and antivirus software, which, deployed on both servers and clients, help protect
computing assets from destruction, and hardware-based authentication and
encryption tools, which guard against privacy loss, identity theft, and data tampering.
Almost all clients now have user log-ins and passwords, but these limited protections
are sometimes left unchanged by the user from the manufacturers' uniform settings
— often common words such as "user" and "password" or just plain blank. And if the
password has been set properly (i.e., to a longish string, say, of at least eight
characters, of mixed letters and numbers that do not make up any common words), a
malicious hacker can still enter the system using a "hammering" algorithm such as
L0PHT, which, by trying a multitude of combinations of characters in rapid fire, can
crack open a standard corporate PC password like a coconut in less than a minute.
More primitive client password schemes — still used in Windows 95 and 98
installations — can simply be bypassed by hitting the Escape key.

©2003 IDC #3577 5
And even with the best of intentions, IT departments do not always upgrade all their
systems with the latest security patches, sent out by application, antivirus, and
operating systems companies when they discover flaws that allow outside
penetration. The hacker community knows about these flaws and cruises the Internet,
looking for systems that lack the updates.
Once inside the network via a vulnerable client node, a hacker with malevolent intent
has all the privileges accorded the legitimate user of that client: access to files,
programs, system resources, and, potentially, other users' PCs. And if the hacker is
sufficiently sophisticated, he may be able to grant himself privileged status and get at
the most sensitive areas of the network, turning computer after computer into a
captive resource. From this position, he can destroy or alter files, corrupt programs,
erase nonvolatile storage devices, and co-opt system resources to carry on further
mayhem.
Thus, even if other security measures — such as physical access control, firewalls,
network security, software security, database encryption, and server-level intrusion
detection — have been instituted, the client node may represent a weak point in the
corporation's armor. Improved authentication on all nodes would help mitigate this
situation. No network is safer than its least-secure node. A full security perimeter
necessarily involves a solid defense at the client level.
THE ADVENT OF ECOMMERCE AND THE RISE IN THE
VALUE OF DATA
Why should client security matter more now than it has in the past? Until recently, few
organizations had a need for systematic data security. Banks and other financial
institutions had to ensure end-to-end security for storing and moving money around
over wires. Certain government agencies could only operate in an impregnable data
fortress. But the volume of valuable data being stored and transmitted by most firms
was relatively low. All that is being changed by the advent of electronic commerce.
A tremendous amount of value is already flowing through the Internet. And far more is
coming. IDC estimates that the value of Internet commerce was $50 billion in 1999,
and this figure will grow by several orders of magnitude to $1.7 trillion worldwide in
2003 (see Figure 1).
This value takes many forms. For individuals, the stakes range from credit card
number loss to identity theft. But for corporations and governments, the value of the
intellectual property inside the computer can be astronomical and, as in the Microsoft
case, sometimes incalculable. However large the threat is to individuals, it is far
greater to corporations. In the corporate world, there are a host of values to be lost —
money, first and foremost. Fraudulent actions can be enormous, in the tens of millions
of dollars in a single transaction. Value is also represented by nonfinancial assets,
such as intellectual property, business plans, and strategic documents. Pilferage of
corporate secrets could lead to a loss of competitive advantage, potentially
condemning a firm to death by slow strangulation.
Once inside the
network via a
vulnerable client
node, a hacker with
malevolent intent
has all the privileges
accorded the
legitimate user of that
client: access to files,
programs, system
resources, and,
potentially, other
users' PCs.

6 #3577 ©2003 IDC
FIGURE 1
WORLDWIDE ECOMMERCE SPENDING BY TYPE, 2000–2003
0
200
400
600
800
1,000
1,200
1,400
1,600
2000 2001 2002 2003
($B)
B2B
B2C
Source: IDC's Internet Commerce Market Model version 8.1, February 2002
Authorities in the United States recently cracked the case of a professional hacker
based in the United Kingdom who had access to about 100 unclassified military
networks during most of 2002. The case, which had been considered a high priority
for a year, despite the unclassified nature of the networks, was a focus because of
the skill of the hacker, who was finally snared. Although the exposed data was not
particularly sensitive, the determination and talent of the hacker led authorities to
believe that it would be only a matter of time before he uncovered something
valuable. Among sites he was able to enter were the Pentagon Picatiny Arsenal in
New Jersey, one of the Army's most delicate research facilities. And he was in the
process of unfolding a multistage attack, the sign of a highly sophisticated hacker, at
the time of his arrest.
In a case involving far greater value, two Russian hackers were lured to the United
States by federal agents on the pretext of a commercial interest. Once in Seattle, they
were arrested. But until that moment, they had been engaged in an operation that had
hacked into banks and ecommerce sites and extorted the operators for money with
the promise of not revealing the hacks to the public. Sometimes the value of
reputation damage is difficult to assess, but it may represent the entire value of the
business. Another Russian hacker was monitored for years as he downloaded
millions of pages of sensitive data from defense department computers, including one
colonel's email inbox.
Aiding and abetting the rise in attacks, the collective pool of hacking knowledge has
risen. Hackers often trade schemes and software via Internet Relay Chat, better
known by its initials, IRC, one of the least-regulated areas of the Internet and one that
allows anonymous contact at the user's discretion. The packets flow to everywhere
from everywhere. And although more policed areas of the Internet exist (e.g., AOL
and other "communities" in cyberspace), the underlying structure still relies on real-
time routing, and packet spoofing makes it possible for someone to conceal his
whereabouts, particularly if he comes from a number of directions at once.
A
iding and abetting
the rise in attacks,
the collective pool of
hacking knowledge
has risen. Hackers
often trade schemes
and software via
Internet Relay Chat,
better known by its
initials, IRC, one of
the least-regulated
areas of the Internet
and one that allows
anonymous contact at
the user's discretion.

©2003 IDC #3577 7
Companies are subject not only to fraud and the direct loss of assets but also to the
value of lost business. When their services are denied by a deliberate overload of
bogus requests, they lose the value of the potential business that would have been
transacted during the period of denial. Another less tangible but perhaps ultimately
more disastrous effect of such attacks is damage to reputation. The harm can be
irreparable. Public confidence in a company may be shaken beyond repair by a
particularly malicious attack or series of attacks. For electronic commerce to function,
customers and partners need to be able to trust the ebusiness process.
And security requirements will only rise as companies turn increasingly to ebusiness.
Although the encryption technologies today are sufficient to guarantee complete
confidence and, mathematically, a user can have perfect assurance that a message
is unique and really did come from the person who says he or she sent it, in order for
the system to be a trustworthy enough medium in which to do business, the
infrastructure must be whole. Given that most companies' security focus is on network
servers, routers, and firewalls, it may be that the client node is the overlooked weak
link in the security chain, but it is by no means the only possible point of penetration.
Breaches can be internal or external. Often, depredations come from the employees
themselves. Employees must be protected from each other so that all intranet users
trust the system. And corporations must be shielded from external threats, hostile
outsiders who may enter the castle from the Internet via the many connections most
firms maintain to communicate with the outside world. For both internal and external
transactions, users must be able to trust and be trusted.
SECURITY TECHNOLOGY: FROM GLOBAL TO LOCAL
Public key encryption and its associated infrastructure address the issue of trust at
the global level. Of the many elements that make up a total security solution,
however, PKI is the most dependent on completeness; that is, any two parties
participating in secure transactions must both agree to rely on a third party, a trusted
authority, sometimes called a certificate authority.
It is because of the complexity of implementing the PKI infrastructure that companies
have recently turned to less ambitious tasks with respect to guaranteeing security at
the client node. Encryption similar to that used to pass keys back and forth over a
network between participants in a PKI scheme can be used to perform far simpler —
but no less important — jobs at the local level. For example, without having to resort
to the network at all, a PC client can provide its user with securely encrypted folders,
the contents of which would look like gibberish to any hacker who managed to open
them. Using one or more authentication techniques (e.g., some combination of
biometric access control, proximity badge, and password), only the legitimate owner
of the locked-away files can open them as readable data. This same type of
authentication can be pressed into service to authorize the client node's user to the
network and all the corporate resources it contains.
THE EVOLUTION OF SECURITY TECHNOLOGY
Security has come a long way since the need for it was first perceived. The
development of security technology has followed both the leapfrog-like need to stay
ahead of the competition and the availability of the means to do it.
The essence of encryption is the systematic altering of text or other data by
mathematical transformations (algorithms), processes that are inherently abstract
(i.e., they can be embodied in either software or hardware). Also critical to the
success of any security scheme is a set of procedures for handling both the original
(clear) and transformed (encrypted) text. In this area, some sets of procedures are
distinctly better than others, as we shall see.

8 #3577 ©2003 IDC
For many years, encryption algorithms were quite simple. The offsets used by Mary
Queen of Scots relied on the slowness of human decipherers, who were often as
much psychologists as mathematicians. If every letter in the encrypted message was,
say, five letters up the alphabet from the original (wrapping around again at Z), then
decoding one word was enough to break the whole text. A bit more complicated
would be incrementing the offset by a fixed amount, which would take a little more
doing on the part of the decipherer but would still yield to trial and error.
These types of techniques were supplanted by the use of "key texts," a method a notch
further up the complexity chain. The offsets to the clear text were determined by the
value of the letters of another text, which could be any written document agreed upon
by both sender and receiver. The document was usually a book, and the key could start
anywhere in the text (say, on the 23rd letter of page 23). This method worked pretty
well, except when the encrypted message was intercepted along with one or the other
of the concealing parties, at which point the shared secret could be "coaxed" out of the
unfortunate soul. These algorithms all depended on the absence of computing power,
which in today's world can perform, in a relatively short period, "brute force" trial-and-
error sequences that a human could never hope to produce in a lifetime.
FROM DES TO AES
One of the first big improvements in security came in 1970, when IBM scientists
developed the Data Encryption Standard (DES). DES starts with something like
offsets but uses complex permutations. The algorithm itself is in the public domain,
but, without the key, the result of any particular instance of usage is nearly opaque.
Essentially, the clear text is broken into groups or blocks of 64 bits and then
transformed using an algorithm dependent on both the message bits and a key, which
is 56 bits long (8 bits being reserved for parity check). This stuff is pretty thorough. As
a rule of thumb, changing one bit of input in the clear text changes the values of half
the output bits in the encoded text. To break this code without the key, a decipherer
has to try 256 or 72,057,594,037,927,936 combinations (72 quadrillion, for those
intimidated by the sight of large numerals), and because of the dynamism of the DES
algorithm, it is extremely difficult to reduce the size of the search space (search-space
reduction being one of the more important techniques at the disposal of decipherers)
other than by luck. Until the mid-1990s, only the National Security Agency had the
computational power to crack a 56-bit DES-encoded message with brute force.
In the mid-1990s, commercially available computing reached a level of performance
sufficient to break DES in a matter of hours, and privacy seekers started using Triple
DES, which essentially runs clear text through the DES washing machine three times,
using a different key on each pass. Triple DES was considered quite secure, requiring
a code breaker to cover a search space of 2112 combinations. The only reason the
search space is not 2168 is that by that time complex cryptoanalytic techniques had
been discovered that reduced the maximum search space. Nonetheless, Triple DES
represented a reprieve for the existing standard. It would still take all the computers
on the Internet more time to crack than the earth is likely to last, not to mention the
human race or something as geologically transient as electricity.
However, even Triple DES had a couple of major weaknesses. It was a symmetric
key encryption method, an Achilles' heel that in some ways makes it no stronger than
the old key-text method. The algorithm is called symmetric because the math to
encrypt a message is simply run backward to decrypt it. This scheme requires both
the sender and recipient to have the same key. Both parties have to share a secret,
and they must be able to exchange that secret secretly. And so the possibility exists
that clever Internet sniffers or bad men with pointy sticks can extract the secret at
either end of the transmission or even in the middle and pop open the message. After
all, the key is just a series of numbers, albeit long ones. In addition, because of the
These algorithms
all depended on the
absence of computing
power, which in
today's world can
perform, in a relatively
short period, "brute
force" trial-and-error
sequences that a
human could never
hope to produce in
a lifetime.

©2003 IDC #3577 9
nature of computer operating environments, DES slows down data flow considerably
when executed in software, and Triple DES slows down the system three times more.
Thus, in the late 1990s, the National Institute of Standards Technology (NIST),
formerly the National Bureau of Standards, put out a call for new algorithms, and a
competition ensued. The specification for the new standard, called Advanced
Encryption Standard (AES), required that it be easily implemented in software, that
the key length be bumped up from 56 to 128 or 256 bits, and that the block size be
increased to 128 bits. With these specifications, AES would be far too large for
anyone using any method to search the key space. After several years, the
competition was narrowed to a few finalists. IBM championed an algorithm called
MARS; cryptographers in Cambridge, England, put forth Serpent; and Schneier
produced a viable competitor, as did RSA Labs. All the finalists' algorithms were
considered more than secure enough, but one written by a couple of cryptographers
in Belgium, Joan Daemen and Vincent Rijmen, called Rijndael (a euphonious, if not
cryptographic, mixing of their names) was chosen partly because it was both fast,
even in software environments, and small.
PUBLIC KEY — STILL BETTER
Despite the speed issue, symmetric key methods are relatively fast because they are
computationally less intensive than other more secure methods. Because they have
relatively less impact on the data rate, they are desirable for encrypting bulk data for
storage and transmission. However, the problem of the shared secret is left unsolved,
even with AES. And so, the best encryption techniques involve doing three things,
which are a combination of technology and procedures: wrapping the shared AES
secret in a much more robustly encrypted envelope, encoding the main message with
AES, and throwing the whole thing away after a single use. One-time usage makes
the value of decryption low to an interceptor, even as the cost is high. As a matter of
jargon, a one-time key is called "ephemeral."
The more robust method used to encode the AES keys is called asymmetric or public
key cryptography. The asymmetry refers to the fact that mathematically related but
different keys are used for encoding and decoding. When the private key is used to
encrypt a message, only the associated public key can be used to decrypt it. When
the public key is used to encrypt a message, only the associated private key can be
used to decrypt it. The public key can be shared with anyone, but the private key
must be kept secret and should only be available to the owner of the key. Knowledge
of the public key does not disclose any information about the private key. The first
asymmetric encryption method to reach commercial usage was brought to market in
the late 1970s by three MIT professors, Ron Rivest, Adi Shamir, and Leonard
Adleman, whose initials just happened to combine to make the name RSA, which is
now the moniker for the de facto standard in public key encryption.
Here are two illustrations of how this type of encryption can be useful. Let's say that
sometime in the near future, you'll be able to vote over the Internet. If every voter has
a pair of private keys safely tucked away in his or her computer, and for every voter a
pair of public keys resides at the statehouse, the courthouse, and the White House,
then when an encrypted vote from you comes in, only the public key associated with
you and only you will be able to decrypt it. Thus, if a vote purports to come from you,
and the vote counter pops it open with your key, then that vote can be guaranteed to
have come from you — assuming your client node is inviolate, which underscores the
need to secure the network at the client end. Going the other way, if I want to send
you a secret note that only you can open, I can encrypt it with your public key, which I
can get because it is public, and only you can open the message. These examples
illustrate two important aspects of security: authentication and privacy.
Rijndael was
chosen partly
because it was both
fast, even in software
environments,
and small.
When the private key
is used to encrypt a
message, only the
associated public key
can be used to
decrypt it.

10 #3577 ©2003 IDC
Public key encryption is based on the idea that some mathematical operations are
easy to do — but hard to undo. A simple example is a square versus a square root. If
you already have the square root of three (which, although approximately
1.73205080756888, has no finite answer), multiplying it by itself easily yields three,
but trying to find the root given only the number three is a lot more difficult. The
essence of the RSA algorithm is the same: Two large prime numbers are easily
multiplied, but factoring the result to find the original numbers is extremely difficult.
Asymmetric encryption starts with two randomly chosen 100-digit prime numbers. The
sender "knows" them or at least has possession and usage of them. They are
multiplied together, and the product becomes one of the two elements in both the
keys. For the other two elements (one each for the public and private keys), one is
chosen from a restricted set that relates to the first two and the other is derived
algorithmically from the product of the first two and the third (the one just chosen).
These four numbers (three, really, since one is shared) are the kernels for RSA
asymmetric encryption. If the public key pair is used to transform clear text via
complex mathematics, then only the private pair can be used to decrypt, via a similar
set of calculations. By the same logic, if the private key pair is used to encode the
clear text, only the public key can be used to decipher it. Although the two key pairs
are interrelated, neither can be derived from the other.
The strength of public key encryption is that it is fantastically robust. Anyone can send
a message encrypted with a public key, but only the holder of the associated private
key can decrypt it. The weakness of asymmetric cryptography is that it is
computationally intensive and would slow down data traffic unacceptably if it were
applied promiscuously. So, as previously mentioned, in practical circumstances it is
used only to encode the symmetric key (i.e., the AES key) used for bulk data
encryption. The result of encoding the symmetric key with an asymmetric public key is
called a "digital envelope," and the process is referred to as "PKI key exchange."
IDENTIFYING THE SENDER AND GUARANTEEING DATA INTEGRITY
We now have an infrastructure robust enough to guarantee the identity of the sender.
The sender is fairly confident of the recipient because only the proper recipient has
the correct private key pair and can turn the message back into clear text. But a
trusted third party (sometimes called the "certificate authority") is required as well —
one that knows all participants and guarantees the identity of the sender. Everybody
has access to the authority's public key pair. Once the sender has proven his or her
identity (through, for example, a handwritten signature, iris scan, voiceprint, or
fingerprint), the authority is able to return a copy of the sender's public key, "signed"
with the authority's private key, and the sender can include this "certificate" in his or
her outgoing message. Thus, you are proven to be you for the purposes of ebusiness.
The signature is simply a secure one-way "hash" of the message itself, encrypted
with a sender's private key. Analogous to a Cyclic Redundancy Check (CRC), the
hash is produced by reducing the message through an algorithm to a "digest," a string
of between 64 and 256 bits. The original message cannot be reconstructed from the
hash by any means because most of the information has been destroyed in the
hashing process. However, the hash is uniquely related to the original message
mathematically. As with the AES algorithm, changing a single bit in the message will
change half the bits in the hash. The hash, encrypted with the sender's private key, is
attached to the message, and at the recipient end, the same math is performed on
the message itself. The recipient decrypts the signature with the sender's public key
and compares the result to the local hash of the message. If the two strings match
perfectly, then the recipient is sure that the sender is authentic and that the message
has not been altered during transmission. Thus, data integrity is assured.