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ABSTRACT
Many organizations are working hard to secure themselves from the
growing threats of message hacking through various trends in
cryptography.Yet the headlines are dominated with the latest news of
message passing disaster more frequently than any time before.This
document intends to review this problem and propose several possible
solutions.The cryptographic industry has been responding to these
threats with ever-quicker responses to the rapid onslaught of malicious
techniques,while corporations establish strict cryptographic
techniques.
Placing an organizations cryptographic techniques at the
desktop level is like closing all the doors in a house¦..while leaving
windows and other entry points open.The present document discusses
various cryptographic techniques of all times such as the three basic
algorithms namely private key algorithm,,public key algorithm and the
hash functions.The need for having three encryption techniques has
also been encrypted .A detailed discussion has been done on the
classical cryptography and the drawbacks of the classical cryptography
to ensure the need for going to new trends in cryptography like quantum
cryptography,elliptic curve cryptography.These new techniques that has
emerged out of various exploitations in the field of cryptography rises
a fair amount of hope that we can over come the problems we are facing
in a headhoc way.These proven technologies can meet the needs of the
most demanding of environments while their respective focus on
manageability has automated many tasks and simplified administrative
functions through easy-to-use interfaces developed through years of
customer feedback..And at the end of the document we can conclude that
soon we can save secrecy involved in message passing from the dangerous
clutches of message hackers.
1.INTRODUCTION
The Internet or the global Internet is the internationally connected
network of computer networks with addresses that are administrated by
IANA (Internet address and Naming Authority). It grew dramatically
because anyone can connect to it and any one connected to it can
connect others to it as well. Each site that connected to it, can
become an Internet Service provider to other sites Does increased
security provide comfort to paranoid people? Or does security provide
some very basic protections that we are naive to believe that we don't
need? During this time when the Internet provides essential
communication between tens of millions of people and is being
increasingly used as a tool for commerce, security becomes a
tremendously important issue to deal with.
There are many aspects to security and many applications, ranging from
secure commerce and payments to private communications and protecting
passwords. One essential aspect for secure communications is that of
cryptography.This paper has two major purposes. The first is to define
some of
the terms and concepts behind basic cryptographic methods, and to offer
a way to compare the myriad cryptographic schemes in use today. The
second is to provide some real examples of cryptography and new trends
in use today.
I would like to say at the outset that this paper is very focused on
terms, concepts, and schemes in current use and is not a treatise of
the whole field.
2.THE PURPOSE OF CRYPTOGRAPHY
Cryptography is the science of writing in secret code
and is an ancient art; the first documented use of cryptography is
writing dates back to circa 1900 B.C. when an Egyptian scribe used non
-standard hieroglyphs in an inscription. Some experts argue that
cryptography appeared spontaneously sometime after writing was
invented, with applications ranging from diplomatic missives to war-
time battle plans. It is no surprise, then, that new forms of
cryptography came soon after the widespread development of computer
communications. In data and telecommunications, cryptography is
necessary when communicating over any untrusted medium, which includes
just about any network, particularly the Internet.
Within the context of any application-to-application communication,
there are some specific security requirements, including:
¢ Authentication: The process of proving one's identity. (The
primary forms of host-to-host authentication on the Internet today are
name-based or address-based, both of which are notoriously weak.)
¢ Privacy/confidentiality: Ensuring that no one can read the
message except the intended receiver.
¢ Integrity: Assuring the receiver that the received message has
not been altered in any way from the original.
¢ Non-repudiation: A mechanism to prove that the sender really
sent this message.
Cryptography, then, not only protects data from theft or alteration,
but can also be used for user authentication. There are, in general,
three types of cryptographic schemes typically used to accomplish these
goals: secret key (or symmetric) cryptography, public-key (or
asymmetric) cryptography, and hash functions, each of which is
described below. In all cases, the initial unencrypted data is referred
to as plaintext. It is encrypted into ciphertext, which will in turn
(usually) be decrypted into usable plaintext.
In many of the descriptions below, two communicating parties will be
referred to as Alice and Bob; this is the common nomenclature in the
crypto field and literature to make it easier to identify the
communicating parties. If there is a third or fourth party to the
communication, they will be referred to as Carol and Dave. Mallory is a
malicious party, Eve is an eavesdropper, and Trent is a trusted third
party.
3.TYPES OF CRYPTOGRAPHIC ALGORITHMS
There are several ways of classifying cryptographic algorithms. For
purposes of this paper, they will be categorized based on the number of
keys that are employed for encryption and decryption, and further
defined by their application and use. The three types of algorithms
that will be discussed are (Figure 1):
¢ Secret Key Cryptography (SKC): Uses a single key for both
encryption and decryption
¢ Public Key Cryptography (PKC): Uses one key for encryption and
another for decryption
¢ Hash Functions: Uses a mathematical transformation to
irreversibly "encrypt" information
A modern crypto device has several essential elements that determine
how it works. First is a crypto algorithm, which specifies the
mathematical transform action that is performed on data to encrypt (or)
decrypt it. Some algorithms are for stream ciphers, which encrypt a
digital data stream a bit at a time, and block ciphers which transform
data in fixed-size blocks, one block at a time the cipher mode defines
how the algorithm is applied block to datastream.
Crypto algorithm is a procedure that takes the plain text data and
transforms it into ciphertext in a reversible way. A good algorithm
produce ciphertext that yields as few clues as possible about either
the key (or) the plain text that produced it.
An important distinction between crypto algorithms is whether they are
secret key (or) public key algorithms.
A secret key algorithm is symmetric, (or) it uses same key for
encryption and also for decryption. The security of secret key
algorithm rests with keeping key itself. Completely secret from others.
Public key algorithm use different keys for encryption an decryption
one key caused private key, must kept secret by its owner and in
general is never shared with anyone else. The other key called public
key will be shared with anyone else. The two will be mathematically
related.
3.1.PRIVATE KEY CRYPTOGRAPHY
A private-key cryptosystem consists of an encryption system E and a
decryption system D. The encryption system E is a collection of
functions E_K, indexed by keys K, mapping some set of plaintexts P
to some set of ciphertexts C. Similarly the decryption system D is a
collection of functions D_K such that D_K(E_K(P)) = P for every
plaintext P. That is, successful decryption of ciphertext into
plaintext is accomplished using the same key (index) as was used for
the corresponding encryption of plaintext into ciphertext. Such
systems, where the same key value is used to encrypt and decrypt, are
also known as symmetric cryptoystems.
3.2.PUBLIC KEY CRYPTOGRAPHY
In a classic cryptosystem, we have encryption functions E_K and
decryption functions D_K such that D_K(E_K(P)) = P for any plaintext
P. In a public-key cryptosystem, E_K can be easily computed from some
public key X which in turn is computed from K. X is published, so
that anyone can encrypt messages. If decryption D_K cannot be easily
computed from public key X without knowledge of private key K, but
readily with knowledge of K, then only the person who generated K can
decrypt messages. That's the essence of public-key cryptography,
introduced by Diffie and Hellman in1976.
3.3. HASH FUNCTIONS
Hash functions, also called message digests and one-way
encryption, are algorithms that, in some sense, use no key (Figure 1C).
Instead, a fixed-length hash value is computed based upon the plaintext
that makes it impossible for either the contents or length of the
plaintext to be recovered. Hash algorithms are typically used to
provide a digital fingerprint of a file's contents, often used to
ensure that the file has not been altered by an intruder or virus. Hash
functions are also commonly employed by many operating systems to
encrypt passwords. Hash functions, then, provide a measure of the
integrity of a file.
4. Why Three Encryption Techniques?
So, why are there so many different types of cryptographic schemes? Why
can't we do everything we need with just one?
The answer is that each scheme is optimized for some specific
application(s). Hash functions, for example, are well-suited for
ensuring data integrity because any change made to the contents of a
message will result in the receiver calculating a different hash value
than the one placed in the transmission by the sender. Since it is
highly unlikely that two different messages will yield the same hash
value, data integrity is ensured to a high degree of confidence.
Secret key cryptography, on the other hand, is ideally suited to
encrypting messages. The sender can generate a session key on a per-
message basis to encrypt the message; the receiver, of course, needs
the same session key to decrypt the message.
Key exchange, of course, is a key application of public-key
cryptography (no pun intended). Asymmetric schemes can also be used for
non-repudiation; if the receiver can obtain the session key encrypted
with the sender's private key, then only this sender could have sent
the message. Public-key cryptography could, theoretically, also be used
to encrypt messages although this is rarely done because secret-key
cryptography operates about 1000 times faster than public-key
cryptography.
5.WHATS WRONG WITH CLASSICAL CRYPTOGRAPHY
The purpose of cryptography is to transmit information in such a way
that access to it is restricted entirely to the intended recipient.
Originally the security of a cryptotext depended on the secrecy of the
entire encrypting and decrypting procedures; however, today we use
ciphers for which the algorithm for encrypting and decrypting could be
revealed to anybody without compromising the security of a particular
cryptogram. In such ciphers a set of specific parameters, called a key,
is supplied together with the plaintext as an input to the encrypting
algorithm, and together with the cryptogram as an input to the
decrypting algorithm.The encrypting and decrypting algorithms are
publicly announced; the security of the cryptogram depends entirely on
the secrecy of the key, and this key must consist of any randomly
chosen, sufficiently long string of bits. Once the key is established,
subsequent communication involves sending cryptograms over a public
channel which is vulnerable to total passive eavesdropping (e.g. public
announcement in mass-media). However in order to establish the key, two
users, who share no secret information initially, must at a certain
stage of communication use a reliable and a very secure channel. Since
the interception is a set of measurements performed by the eavesdropper
on this channel, however difficult this might be from a technological
point of view, in principle any classical key distribution can always
be passively monitored, without the legitimate users being aware that
any eavesdropping has taken place.
Mathematicians have tried hard to solve the key distribution problem.
The 1970s brought a clever mathematical discovery in the shape of
``public key" systems [1,2]. In these systems users do not need to
agree on a secret key before they send the message. They work on the
principle of a safe with two keys, one public key to lock it, and
another private one to open it. Everyone has a key to lock the safe but
only one person has a key that will open it again, so anyone can put a
message in the safe but only one person can take it out. These systems
exploit the fact that certain mathematical operations are easier to do
in one direction than the other. The systems avoid the key distribution
problem but unfortunately their security depends on unproven
mathematical assumptions, such as the difficulty of factoring large
integers (RSA - the most popular public key cryptosystem gets its
security from the difficulty of factoring large numbers. This means
that if and when mathematicians or computer scientists come up with
fast and clever procedures for factoring large integers the whole
privacy and discretion of public-key cryptosystems could vanish
overnight. Indeed, recent work in quantum computation shows that
quantum computers can factorize much faster than classical computers .
6.NEW TRENDS IN CRYPTOGRAPHY
6.1. Elliptic Curve Cryptography
In general, public-key cryptography systems use hard-to-solve problems
as the basis of the algorithm. The most predominant algorithm today for
public-key cryptography is RSA, based on the prime factors of very
large integers. While RSA can be successfully attacked, the mathematics
of the algorithm have not been comprised, per se; instead,
computational brute-force has broken the keys. The defense is "simple"
†keep the size of the integer to be factored ahead of the
computational curve! In 1985, Elliptic Curve Cryptography (ECC) was
proposed independently by cryptographers Victor Miller (IBM) and Neal
Koblitz (University of Washington). ECC is based on the difficulty of
solving the Elliptic Curve Discrete Logarithm Problem (ECDLP). Like the
prime factorization problem, ECDLP is another "hard" problem that is
deceptively simple to state: Given two points, P and Q, on an elliptic
curve, find the integer n, if it exists, such that p= nQ. Elliptic
curves combine number theory and algebraic geometry. These curves can
be defined over any field of numbers (i.e., real, integer, complex)
although we generally see them used over finite fields for applications
in cryptography. An elliptic curve consists of the set of real numbers
(x, y) that satisfies the equation:
y2 = x3 + ax + b
The set of all of the solutions to the equation forms the elliptic
curve. Changing a and b changes the shape of the curve, and small
changes in these parameters can result in major changes in the set of
(x,y) solutions.
Figure shows the addition of two points on an elliptic curve. Elliptic
curves have the interesting property that adding two points on the
elliptic curve yields a third point on the curve. Therefore, adding two
points, P1 and P2, gets us to point P3, also on thecurve. Small changes
in P1 or P2 can cause a large change in the position of P3.So let's go
back to the original problem statement from above. The point Q is
calculated as a multiple of the starting point,
P, or, Q = nP. An attacker might know P and Q but finding the integer,
n, is a difficult problem to solve. Q is the public key, then, and n is
the private key.
6.2.QUANTUM CRYPTOGRAPHY
The Heisenberg uncertainty principle and quantum entanglement can be
exploited in a system of secure communication, often referred to as
"quantum cryptography". Quantum cryptography provides means for two
parties to exchange a enciphering key over a private channel with
complete security of communication. There are at least three main types
of quantum cryptosystems for the key distribution, these are:
(A)
Cryptosystems with encoding based on two non-commuting observables
proposed by S.Wiesner (1970), and by C.H.Bennett and G.Brassard (1984)
(B) Cryptosystems with encoding built upon quantum entanglement and the
Bell Theorem proposed by A.K.Ekert (1990)
© Cryptosystems with encoding based on two non-orthogonal state
vectors proposed by C.H.Bennett (1992)
Quantum cryptosystem (A) can be explained with the following simple
example. The system includes a transmitter and a receiver. A sender may
use the transmitter to send photons in one of four polarisations: 0,
45, 90, or 135 degrees. A recipient at the other end uses the receiver
to measure the polarisation. According to the laws of quantum
mechanics, the receiver can distinguish between rectilinear
polarisations (0 and 90), or it can quickly be reconfigured to
discriminate between diagonal polarisations (45 and 135); it can never,
however, distinguish both types. The key distribution requires several
steps. The sender sends photons with one of the four polarisations
which are chosen at random. For each incoming photon, the receiver
chooses at random the type of measurement: either the rectilinear type
or the diagonal type. The receiver records the results of the
measurements but keeps them secret. Subsequently the receiver publicly
announces the type of measurement (but not the results) and the sender
tells the receiver which measurements were of the correct type. The two
parties (the sender and the receiver) keep all cases in which the
receiver measurements were of the correct type. These cases are then
translated into bits (1's and 0's) and thereby become the key. An
eavesdropper is bound to introduce errors to this transmission because
he/she does not know in advance the type of polarisation of each photon
and quantum mechanics does not allow him/her to acquire sharp values of
two non-commuting observables (here rectilinear and diagonal
polarisations). The two legitimate users of the quantum channel test
for eavesdropping by revealing a random subset of the key bits and
checking (in public) the error rate. Although they cannot prevent
eavesdropping, they will never be fooled by an eavesdropper because
any, however subtle and sophisticated, effort to tap the channel will
be detected. Whenever they are not happy with the security of the
channel they can try to set up the key distribution again.
The basic idea of cryptosystems (B) is as follows. A sequence of
correlated particle pairs is generated, with one member of each pair
being detected by each party (for example, a pair of so-called
Einstein-
Podolsky-Rosen photons, whose polarisations are measured by the
parties).
An eavesdropper on this communication would have to detect a particle
to read the signal, and retransmit it in order for his presence to
remain unknown. However, the act of detection of one particle of a pair
destroys its quantum correlation with the other, and the two parties
can easily verify whether this has been done, without revealing the
results of their own measurements, by communication over an open
channel.
CONCLUSION
We use different types of algorithms to establish
security services in different service mechanisms.We use either private
key cryptography or public key cryptography according to requirement.If
we want to send message quickly we use private key algorithm and if we
want to send messages secretely we use public key algorithm.
Hence let us hope that the NEW TRENDS of cryptography saves the
messages from the DANGEROUS CLUTCHES OF MESSAGE HACKERS.
I N D E X
1. INTRODUCTION
2. CRYPTOGRAPHY-PURPOSE
3. TYPES OF CRYPTOGRAPHIC ALGORITHMS
3.1 PRIVATE KEY ALGORITHM
3.2 PUBLIC KEY ALGORITHM
3.3 HASH FUNCTIONS
4. WHY THREE ENCRYPTION TECHNIQUES?
5. CLASSICAL CRYPTOGRAPHY-DRAWBACKS
6. NEW TRENDS IN CRYPTOGRAPHY
6.1 ELLIPTIC CURVE CRYPTOGRAPHY
6.2QUANTUM CRYPTOGRAPHY
7. CONCLUSION
BIBILIOGRAPHY
