Suppose we want to transmit data that describes the details of a wire transfer.
ID: 3677315 • Letter: S
Question
Suppose we want to transmit data that describes the details of a wire transfer. To do so, we use a public file format with adequately sized fixed-length fields that specify the transaction details (account numbers involved, names of sender and recipient, purpose of the transaction, amount to be transferred, time and date, a sequence number for the transaction). To protect the data during transmission we encrypt it by means of a stream cipher: We produce a secret pseudo-random sequence that is XORed bit-by-bit with the plaintext data specifying the wire transfer.
Why is this cryptographic protection inadequate, even if the stream cipher is accepted as being strong?
Explanation / Answer
. Cryptooperation is a process of replacement and/or rearrangement of some or another symbols (bytes, bits) of an initial message using a special algorithm in accordance with the given key (a kind of a password).
There are two types of cryptooperation in cryptology: symmetrical and asymmetrical. The first is sometimes called “a one-key cipher” or a cipher with a secret key. Symmetry lies in one secret key used for encryption and deciphering of one message. Symmetrical ciphers are best suited for cases when computer information is just stored on the hard disk, floppies or other mediums. One-key ciphers are very foolproof, but are rarely used when, for example, you may need to send a closed message through e-mail. The answer is that if the user protects his letter with a symmetrical cipher, then he needs to send a key by some other way. However many users regard that this way cannot absolutely guarantee total inviolability of the message in transit.
Cryptography has long been of interest to intelligence gathering and law enforcement agencies. Secret communications may be criminal or even treasonous. Because of its facilitation of privacy, and the diminution of privacy attendant on its prohibition, cryptography is also of considerable interest to civil rights supporters. Accordingly, there has been a history of controversial legal issues surrounding cryptography, especially since the advent of inexpensive computers has made widespread access to high quality cryptography possible.
A stream cipher is a method of encrypting text (to produce ciphertext) in which a cryptographic key and algorithm are applied to each binary digit in a data stream, one bit at a time. This method is not much used in modern cryptography. The main alternative method is the block cipher in which a key and algorithm are applied to blocks of data rather than individual bits in a stream.
So to provied spme better security functionalities regarding the user transactions we used cryptiographic transaction even if stream cipher is accepted as strong....