A code is a rule for converting a piece of information (for example, aletter, word, phrase, or gesture) into another form or representation(one sign into another sign), not necessarily of the same type.Encoding is the process by which information from a source isconverted into symbols to be communicated. Decoding is thereverse process, converting these code symbols back intoinformation understandable by a receiver.One reason for coding is to enable communication in places whereordinary spoken or written language is difficult or impossible.
The simplest form of a code is the "jargon code", in whicha particular arbitrary phrase is used as code.Jargon codes have been used for a long time, most significantly in World War II, when they were used to send commands over broadcast radio to resistance fighters “BOXER SEVEN SEEK TIGER5 AT RED CORAL” This uses "code words" to report that a friendly military force code named BOXER SEVEN is now hunting an enemy force code named“The nightingale sings at dawn” -- TIGER5 at a location codenamed RED corresponds to a particular CORAL. This particular code is weakpredefined message and the actual meaning of this might be: “The in that the "SEEK" and "AT" wordssupply drop will take place at 1hrs provide information to a code breaker tomorrow”. on the structure of the message. In practice, military codes are often defined as "code numbers" rather than code words, using a codebook that provides a dictionary of code numbers and their equivalent words.
Caesar cipher used by Julius Caesar to communicate with his army. Caesar is considered to be one of the first persons to have ever employed encryption for the sake of securing messages. Caesar decided that shifting each letter in the message would be his standard algorithm, and so he informed all of his generals of his decision, and was then able to send them secured messages. Using the Caesar Shift (3 to the right), the message, "RETURN TO ROME" would be encrypted as, "UHWXUA WR URPH’’ Thus, the Caesar cipher is a shift cipher since the ciphertext alphabet is derived from the plaintext alphabet by shifting each letter a certain number of spaces.
A B C D E F G H I J D E F G H I J K L M K L M N O P Q R S T N O P Q R S T U V W THE FAULT, DEAR BRUTUS, LIES NOT IN OUR STARS BUT IN OURSELVES. would be enciphered as MAX YTNEM, WXTK UKNMNL, EBXL GHM BG HNK LMTKL UNM BG HNKLXEOXL.
• A code is a system of signals that is used to represent letters or numbers in transmitting a message. In otherCODES words, a code deals with phrases and sentences or whole words. For example, this symbol means: = "Send help at once. • A cipher deals with letters. It is a message written in letters in a predetermined code. This means that aCIPHERS cipher is a system of communication that uses letters instead of phrases and such.
•Aftergetting a hang of code- breaking by shifting the lettersforward and backwards, it is realized that there are 25 possibleway of deciphering a message. Further, in an attempt to securemessages, symbols were used, vis a vis, A as =, B as * etc.•So, what about coding messages another way? For a long time, people thought this type of code would be reallyhard to crack. It would take the enemy far too long to figure outwhat letter of the alphabet each symbol stood for just by trying allthe possible combinations of letters and symbols. There are 400million billion billion possible combinations!!!!
A special type of code was used by Mary Queen of Scots when she wasplotting against Elizabeth the First. Mary wanted to kill Elizabeth sothat she herself could become Queen of England and was sendingcoded messages of this sort to her co-conspirator Anthony Babington.Unfortunately for Mary, there is a very simple way of cracking thiscode that doesnt involve trial and error, but which does involve,surprise, surprise, maths. Letter sent by Mary Queen of Scots to her co-conspirator Anthony Babington. Every symbol stands for a letter of the alphabet.
Way of solving the message: Letters in a language are pretty unusual because some get used more often than other letters. In most of dictionary words and names have the letter ‘’e’’, which most frequently occurs, then ‘t’, then ‘a’, as shown below:
All Elizabeth the Firsts Spy-Master had to do to crack Marys code, was to look through the coded message and count the number of times each symbol came up. The symbol that came up the most would probably stand for the letter E. When you crack codes like this, by looking for the most common letter, its called frequency analysis, and it was this clever method of cracking codes that resulted in Mary having her head cut off. CHOP!!! Modern cryptography involves disciplines of computer, mathematics and engineering. Various coding/decoding methods are extensively used in communication and computer technology , for storage and transmission purpose.
Semaphore, is a method of coding , where the configuration of flags held by a signaller or the arms of a semaphore tower, encodes parts of the message, typically individual letters and numbers. Another person standing a great distance away can interpret the flags and reproduce the words sent. Chappe telegraph, or Napoleonic semaphore is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a fixed position. Semaphore are virtually used to transmit information over long distances. Some semaphore used which are used in navigation ships for maritime security through visual signals or hand- held flags are:
Although the machine wasEnigma machines were used by initially invented forGerman military for encryption commercial purposes in Bank , and decryption of the secret however it was found to bemessages during the world war useful and extensively used II. during war period. When a key is pressed, the The Enigma machine is a circuit gets completed with combination of mechanical and current flowing through various electrical subsystems , components and ultimatelyconsisting of key boards, a set of lighting the display lamp rotors and electrical circuits. indicating the output letter.
The Polish & British mathematicians made great effort to understand this machine and developed decryption methods. The machine was based on mathematical models of encryption . SET OF ENIGMA ROTORS
it was also extensively When using morse Morse code is a method used for early radio code, a dash is equal to for transmitting communication three dots. A space information, using beginning in the 1890s. between parts of the standardized sequences However, with the of short and long marks same letter is equal to development of more or pulses - commonly one dot. A space advanced known as "dots" and between two letters is communications"dashes" - for the letters, equal to three dots and technologies, the numerals, punctuation a space between two widespread use of Morseand special characters of words is equal to five code is now largely a message. dots. obsolete.