undergraduate thesis
The Vigenère and the Playfair Cipher

Marinela Knežević (2015)
Sveučilište Josipa Jurja Strossmayera u Osijeku
Odjel za matematiku
Zavod za teorijsku matematiku
Katedra za algebru i matematičku analizu
Metadata
TitleVigenèreova i Playfairova šifra
AuthorMarinela Knežević
Mentor(s)Mirela Jukić Bokun (thesis advisor)
Abstract
Vigenèreova šifra je metoda šifriranja teksta koja koristi serije različitih Cezarovih šifri na osnovi ključne riječi. U 16. stoljeću je šifru prvi opisao Giovan Battista Bellaso, dok je Blaise de Vigenère osmislio šifru s autoključem. Otkriće metode je pogrešno pripisano Blaise de Vigenèreu u 19. stoljeću i danas je poznata kao " Vigenèreova šifra". Premda je šifra lagana za razumijevanje i implementaciju, kroz tri se stoljeća odupirala svim pokušajima razbijanja, zbog čega je stekla opis "le chire indechirable", francuski za neprobojnu šifru. Ipak, pokazalo se da se šifra može razbiti metodama za određivanje duljine riječi i samim odredivanjem ključne riječi. Playfairova šifra je jednostavna, ali učinkovita šifra koja se bazira na tome da se parovi slova šifriraju korištenjem 5 × 5 matrice. Šifru zapravo nije izumio barun Playfair nego fizičar i izumitelj Charles Wheatstone u 19. stoljeću. Playfairova uloga bila je popularizirati ju. Isprva, šifra je smatrana prekompliciranom te se nije koristila često. No, pokazalo se da je jednostavnija za korištenje od većine drugih šifara koje su onda bile u uporabi. Ova šifra se razbija korištenjem analize frekvencije bigrama. U radu su definirane Vigenèrova i Playfairova šifra te je na primjerima prikazan način šifriranja i dešifriranja u svakom od ovih kriptosustava.
Keywordscryptology cryptography cryptoanalysis key plaintext ciphertext en- cryption decryption cryptosystem Vigenère cipher Kasiski examination index of coincidence Playfair cipher probably word method
Parallel title (English)The Vigenère and the Playfair Cipher
GranterSveučilište Josipa Jurja Strossmayera u Osijeku
Odjel za matematiku
Lower level organizational unitsZavod za teorijsku matematiku
Katedra za algebru i matematičku analizu
PlaceOsijek
StateCroatia
Scientific field, discipline, subdisciplineNATURAL SCIENCES
Mathematics
Other Mathematical Disciplines
Study programme typeuniversity
Study levelundergraduate
Study programmeUniversity undergraduate study programme in mathematics
Academic title abbreviationuniv.bacc.math.
Genreundergraduate thesis
Language Croatian
Defense date2015-09-15
Parallel abstract (English)
The Vigenère cipher is a method of encrypting alphabetic text by using series of different Caesar ciphers based on the letters of a keyword. The method was originally described by Giovan Battista Bellaso in 16th century, while Blaise de Vigenère created autokey cipher. The invention was later missattributed to Blaise de Vigenère in the 19th century and is now widely known as the "Vigenère cipher". Though the cipher is easy for understanding and implementation, for three centuries it resisted all attempts to break it; this is why it earned the description "le chire indechirable", french for the indecipherable cipher. However, it appeared that the cipher can be broken by using methods for determining length of a keyword and determining a keyword. The Playfair cipher is a simple but eective cipher in which pairs of letters are encryp- ted using the 5×5 matrix. The cipher was actually invented not by Baron Playfair, but by the physicist and inventor Sir Charles Wheatstone in 19th century. Playfair's main role was to popularize it. Initially, the cipher was turned down because it was thought to be too complicated. But, it turned out to be easier to use than almost all the ciphers that were then in use. This cipher can be broken by using the analysis of bigrams frequencies. The Vigenère and the Playfair cipher are dened in this work. Also, methods of encryption and decryption in each of this cryptosystems are shown on examples.
Parallel keywords (Croatian)kriptologija kriptografija kriptoanaliza ključ otvoreni tekst šifrat šifriranje dešifriranje kriptosustav Vigenèreova šifra Kasiskijev test indeks koincidencije Playfairova šifra metoda vjerojatne riječi
Resource typetext
Access conditionOpen access
Terms of usehttp://rightsstatements.org/vocab/InC/1.0/
URN:NBNhttps://urn.nsk.hr/urn:nbn:hr:126:112491
CommitterMirna Šušak Lukačević