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PLEJFEROVA ŠIFRA
PLAYFAIR CIPHER

Autor: Bojan Babić I-8, Šesta beogradska Gimnazija
Mentori: Vesna Rajšić, dipl. matematicar i Violeta Komnenović, dipl.matematicar

REZIME

Kriptologija, kao nauka koja pre svega zahteva da bude unapreĊivana, prolazila je kroz brojna poboljšanja
svojih šifrata. Zbog potrebe drugih ljudi da saznaju podatke koji nisu bili namenjeni njima, ti šifrati su redom

gubili na svojoj ,,snazi”. Jedan od znaĉajnijih naĉina šifrovanja jeste upravo playfairova šifra.

Osmislio ju je Ĉarls Vitston u 19. veku. On je 1854. godine uvideo da se substicija i transpozicija mogu
spojiti, odnosno da se iz njih moţe izvući ono najbolje i pretoĉiti u tada savršeni šifrat. Naravno, trebalo mu

je dosta vremena dok nije osmislio takav naĉin šifrovanja, ĉije ime je dao po svom prijatelju Plejferu.
Plejferova šifra je dugo bila veoma korišćena i ubrzo ,,potisnula” sve ostale naĉine šifrovanja koji su mu

prethodili. Ali, put kojim je Ĉarls progurao svoju šifru nije bio tako lak.

Bilo je mnogo skeptika koji su pokušavali da pokaţu ljudima koliko je Plejferova šifra zapravo opasna za
podatke, izmišljali su mnoge teoreme kojima bi uspeli da zavaraju javnost, sve dok Ĉarls nije dokazao

sigurmost ove šifre. Naravno, Plejferova šifra je našla svoj put do slave i postala jedna od najpoznatijih
naĉina šifrovanja.

SUMMARY

Cryptography, as a science which, above all, needs to be developed, has gone through numerous cipher
improvements. Due to the need of other people to get to know the information which was not meant for them
to know, the ciphers, one by one, became weaker and weaker. One of the important ways of encryption is by
the means of the Playfair cipher.

It was invented in the nineteenth century by Charles Wheatstone. In 1854 Charles saw that substitution and
transposition could be connected, i.e. that one could extract what is the best in the two processes, and put it
in the cipher which was considered to be perfect at that time. Of course, he needed a lot of time to think of
such a way of encryption, and it was named after a friend of his, Playfair. Playfair cipher was being used for
a long time, and soon it replaced all the other previous processes of encryption. Yet, the way in which
Charles had to prove that his cipher was a proper one, was not so easy.

There has been many sceptics who have tried to show people how dangerous Playfair cipher in reality is for
the information. They have made up various theories which were supposed to mislead the public, untill
Charles proved how safe the cipher was. Playfair cipher has, of course, found its way to fame, and has
become one of the most famous processes of encryption.