New Trends In CRYPTOGRAPHY TECHNOLOGY

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)

(C) 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.