26-11-2012, 05:02 PM
THE RSA PUBLIC KEYS CRYPTOSYSTEM AND ITS PRIVATE KEY FOR INCREASED SECURITY IN GROUP COMMUNICATION
RSA PUBLIC KEYS.doc (Size: 75.5 KB / Downloads: 114)
ABSTRACT
When one transmits data over a packet -switched network, like the Internet, a packet
sniffer at any node along the transmission path can detect packets with potentially useful information. Unfortunately, some of this information (for example, credit card numbers or other private information) is most useful
to people with dishonorable (and often criminal) intentions. As commerce over the Internet – and other vulnerable long-distance networks – increases, this problem becomes more critical. Private data stored on a computer that’s accessible over a
network is also vulnerable. One solution to this problem is to use two different keys – one for encryption and the other for decryption. SENDER could then send his/her encryption key to RECEIVER, who could use it to send an encoded message, back to Alice. Provided Alice keeps her decryption key private, no one who intercepts the message will be able to decode it. In fact, SENDER could make his/her encryption key publicly available, so that anyone else who wants to do so can send her an encoded message. So long as she keeps her decryption key secret, no one else will
be able to read messages meant only for SENDER.
INTRODUCTION
Like all public-key systems, the keys are derived using a “trapdoor” operation – an operation that is easy to do but difficult to “undo.” In RSA, this operation is the multiplication of two large prime numbers: it is easy and fast to multiply the two numbers together, but it is significantly more difficult and time consuming to factor
the resulting number back into its prime components. In this lab experience, you will be using relatively small primes (only three digits) to see how this system works.
RELATED WORK
Cryptography has come to be understood to be the science of secure communication [1].The publication in 1949 by C. E. Shannon of the paper Communication Theory of Secrecy Systems [2] ushered in the era of scientific secret-key cryptography. However, Shannon’s 1949 paper did not lead to the same explosion of research in cryptography that his 1948 paper had triggered in information theory [3]. The real explosion came with the publication in 1976 by W. Diffie and M. E. Hellman of their paper, New Directions in Cryptography [4]. Diffie and Hellman showed for the first time that secret communication was possible without any transfer of a secret key between sender and receiver, thus establishing the turbulent epoch of public-key cryptography. Moreover, they suggested that computational complexity theory might serve as a basis for future research in cryptography.
BANK ACCOUNT TRANSACTIONS IN ATM USING RSA ALGORITHM
[11]We will implement the authentication and secure communications protocols for a distributed system consisting of a bank server and a number of automatic teller machines (ATMs). The computer system at the bank is connected using insecure communications channels to the ATMs. The insecure communications channels are subject to attack by active and passive wiretappers: messages may not be deleted by an attacker, but messages sent might be read, replayed, or changed by an attacker, and new messages might be generated by an attacker. Thus, the authorship and/or content of messages that transit the insecure communications link should be considered suspect.
Customers use ATMs to make queries, withdrawals, and balance inquiries involving their accounts. Attackers must be prevented from interfering with these actions. Unlike ATM
machines typically used in the US today, the ATM machines in the project accept smartcards capable of storing an RSA private key and performing a small amount of computation. Interactions with the ATM would work like this:
IMPORTANCE OF KEY SIZE
[10]Keys are used to control the operation of a cipher so that only the correct key can convert encrypted text (ciphertext) to plaintext. Many ciphers are based on publicly known algorithms or are open source, and so it is only the difficulty of obtaining the key that determines security of the system, provided that there is no analytic attack (i.e., a 'structural weakness' in the algorithms or protocols used), and assuming that the key is not otherwise available (such as via theft, extortion, or compromise of computer systems).
A key should therefore be large enough that a brute force attack (possible against any encryption algorithm) is infeasible – i.e, would take too long to execute. Shannon's work on information theory showed that to achieve perfect secrecy, it is necessary for the key length to be at least as large as the message to be transmitted and only used once (this algorithm is called the One-time pad). In light of this, and the practical difficulty of managing such long keys, modern cryptographic practice has discarded the notion of perfect secrecy as a requirement for encryption, and instead focuses on computational security. Under this definition, the computational requirements of breaking an encrypted text must be infeasible for an attacker.
CONCLUSION AND FUTURE WORK
As commerce over the Internet – and other
vulnerable long-distance networks –
increases, this problem becomes more
critical. Private data stored on a computer
that’s accessible over a network is also
vulnerable.
One solution to this problem is to encipher
data one wants to keep private. In other
words, one can somehow “scramble” the
data so that it’s unrecognizable to anyone
who does not have the necessary key to
“unscramble” – or decipher – it. In socalled
“traditional” encryption techniques,
the same key is used for enciphering (or
encryption) and deciphering (or decryption).
The key is typically a large number that is
used to mathematically transform the
message. The problem then becomes the
secure transmission of the key itself.
Another solution to this problem is to use
two different keys – one for encryption and
the other for decryption.