SolutionIn cryptography, a substitution cipher is a mechanism of encrypting in which the words of plaintext are substituted with ciphertext, with respect to a static system; the individual “units” may be letters , group of 2 or 3 letters, mixtures of them, etc. It actually constitutes of replacing every plaintext letter for a different ciphertext letter. It is differect from the Caesar cipher in that the cipher alphabet is not simply the alphabet shifted by a particular value , it is completely jumbled in an unreadable format .Here is the key to a simple substitution cipher: Plaintext letters: abcdefghijklmnopqrstuvwxyzCiphertext letters: EKMFLGDQVZNTOWYHXUSPAIBRCJ The key gives the relationship between a plaintext letter and its substituted ciphertext letter.
Using this particular key, every plaintext letter a would be replaced by ciphertext E, every plaintext letter e by L, etc. The plaintext 1 message simple substitution cipher would becomeSVOHTL SAKSPVPAPVYW MVHQLU. The steps to encrypt a short text :Firstly , obtain the text you want to encrypt in the readable(plaintext) format .Decide the key which we want to use that obtains the correspondence between plaintext character and ciphertext character . For this example we will use the following keyPlaintext letters: abcdefghijklmnopqrstuvwxyzCiphertext letters: EKMFLGDQVZNTOWYHXUSPAIBRCJ Now for each of the characters in the plain text , substitiute it for the cioher text . This will give you the encrypted message that can be read only with the key .
The text message is as follows In those days Mr Sherlock Holmes was still living in Baker Street and the Bastables were lookingfor treasure in the Lewisham Road. In those days, if you were a boy you had to wear a stiff Etoncollar every day, and schools were usually nastier than now. But meals were nicer; and as forsweets, I won’t tell you how cheap and good they were, because it would only make your mouthwater in vain. And in those days there lived in London a girl called Polly Plummer.The corresponding cipher text is as follows VWPQYSLFECSOUSQLUTYMNQYTOLSBESSPVTTTVIVWDVWKENLUSPULLPEWFPQLKESPEKTLSBLULTYYNVWDGYUPULESAULVWPQLTLBVSQEOUYEFVWPQYSLFECSVGCYABLULEKYCCYAQEFPYBLEUESPVGGLPYWMYTTEULILUCFECEWFSMQYYTSBLULASAETTCWESPVLUPQEWWYBKAPOLETSBLULWVMLUEWFESGYUSBLLPSVBYWPPLTTCYAQYBMQLEHEWFDYYFPQLCBLULKLMEASLVPBYATFYWTCOENLCYAUOYAPQBEPLUVWIEVWEWFVWPQYSLFECSPQLULTVILFVWTYWFYWEDVUTMETTLFHYTTCHTAOOLU