Applications of cryptography

encounter for the scoop up websites in cryptanalysis is a daunting, if not an impossible task. This is beca example, as I started searching the Web for interesting sites on coding, I launch that there atomic number 18 vindicatory so umpteen. The task is make even more difficult by the fact that cryptanalytics is such(prenominal) a broad subject which encompasses several sub-subjects. Nevertheless, I have to choose three sites. Basically, I nevertheless set devil criteria for choosing a site it has to be interesting and it has to be easily understand qualified even when the satiate is technical.Being a history enthusiast, my search for riveting contents led me to a website that features cryptology in the sixteenth and 17th centuries. It usher out be accessed via the link http//home. att. realize/tleary/cryptolo. htm and is create verbally by Thomas (Penn) Leary. One of the reasons I was drawn to this site is the existence of an pen for the site. With internet access and blogging accessible to approximately everyone, I tend to get funny of websites whose sources are unknown for I feel that this lessens the reliability of the site and its contents, unless the site belongs to a compevery or organization whose reliability gutternot be questioned.The content starts with a philosophic statement by Blaise de Vigenere, both(prenominal)thing which I put in rather a endearing. Being primarily a non-technical site, it avoids the use of cryptographic jargon and alternatively uses words easily understandable by almost any reader. Examples of the world-class kinds of cryptology such as the Elizabethan cryptology (uses numbers to en code letters) were discussed in the site. some(prenominal) paragraphs in the site are attributed to Johannes Trithemius, a German monk who is excessively considered the prototypic theoretician in coding.Most of his schemes in any case implicate steganography, a close cousin to cryptography, which involves privac y the existence of the message itself. Aside from that, Trithemius contributed oftentimes to the existence of poly alphabeticity. His tableau, which he called his tabula recta, uses the normal alphabet in various positions as the think alphabets. Giovanni Battista della Porta, an separate famous early cryptographer original a highlight in the site. Likewise, the use of acrostic, a naught which involves exploitation the first letters of a poem in order to appoint a word, was also adjudgen emphasis.Poets in the Italian Renaissance and during the Elizabethan period were inform to be kinda fond in using acrostic. Although quite non-technical, this website appealed to me because I disregard look back and trace the early days of cryptology when there were no computers and other modernistic crypto graphing equipment. It is fascinating to raze that the state-of-the-art cryptography used immediately evolved from relatively simple ciphers such as Trithemius tableau and acrostic. In terms of info presentation, the website did quite hale(p) and the information was ordered in a clear and self-opinionated manner.Furthermore, the author cited several kit and caboodle which I find commendable as most of the websites today obtain information from other sites, books and journals without acknowledging these sources. As for the technical side, I found David Wagners (1999) discussion of the spear thrower ardor quite interesting. His topic can be accessed by this link lasecwww. epfl. ch/intranet/proceedings-iacr-98-03/ text file/1636/16360156. pdf, although I deliberate it originally came from www. cs. berkeley. edu/daw/papers/ dart thrower-fse99. ps. As you might have sight Im quite a stickler for the reliability of website contents.Apart from the topic being quite interesting, I chose this website because it came from an academic institution, which I believe screens articles and papers before posting it in their website. Even for non-technical readers, Wag ners (1999) introduction to the purpose of a backfire attack is quite comprehensible. He started by describing derived function cryptanalysis, a powerful cryptanalytic technique. Because of such power, derived function analysis has been used to break many published ciphers. Block cipher designers and so ensure that their design is secured from differential attacks.Algorithm designers usually compute an upper bound p on the probability of any differential characteristic on the cipher. The designer then invokes an often repeated folk theorem stating that any successful differential attack result require at least 1/p texts to break the cipher, thus devising a conclusion that the cipher is galosh from differential attacks. In order to fold this folk theorem false, Wagner (1999) exhibited an attack in this carapace the spear thrower attack that allows an opponent to outsmart the 1/p bound in some cases.Lets say the best characteristic for half of the rounds of the cipher has a probability of q, a successful backfire attack volition therefore regard O (q-4) chosen texts. In some cases, q-4 1/p, in which case the boomerang attack will be able to beat the folk theorems bound. Basically, a boomerang attack is lifelessness a differential-style attack but does not deliver to cover the whole cipher with a wizard pattern having a importantly large probability. Instead, the attacker tries to find two highly-probable patterns, though not necessarily relate to each other, but when taken together can cover the whole cipher (Standaert, Piret, Quisquater, 2003).Wagner (1999) does not only discuss boomerang attack theoretically and only with probabilities, he showed how boomerang attack can be used to break COCONUT98, a cipher that rely on decorrelation techniques for its design. The jailbreak of COCONUT98 suggests that decorrelation design may fail to give enough security against advance differential attacks when caution is not taken. Therefore the us e of decorrelation techniques is not a total plug of safety against differential-style attacks.Nevertheless, a decorrelation design still improves the ciphers security such that in the absence of a decorrelation module, COCONUT98 will be more vulnerable to conventional differential-style attacks. Wagner (1999) also demonstrated the use of boomerang attacks on Khufu and FEAL, and included a translation of inside-out attack, a twofold to boomerang attack, with the boomerang attack work from the outside, while the inside-out attack works from the inside. In general, the site is very edifying but I must admit, quite technical.One therefore does not approach it without having received a background on cryptology. Oliver Pells (nd) website, which he claims has won him a esteem in a mathematics act contest, is just as interesting. Accessed from http//www. ridex. co. uk/cryptology/_Toc439908875, it presents a very useful overview of cryptology. Slightly technical, it comes in between the first two websites. Whereas the first is unimpeachably non-technical while Wagners (1999) paper is definitely technical, Pell (nd) presents technical data in the simplest way possible.In fact, among the three sites, this one definitely stands out. The website content begins with the translation of commonly-used cryptographic terms, an singularity that the paper is meant to be read by a wide range of hearing including non-technical ones. The history of cryptography and cryptanalysis which followed the definition is quite fascinating and seems to me, well-researched. Ancient Egyptians, Hebrews and Assyrians already developed a crude form of cryptographic systems.Later on, the Greeks invented the first transposition cipher but it was the Arabs who were the first to have a clear grasp on the principles of cryptography and elucidated the beginning of cryptanalysis. In the more modern times, the uses of cryptography during the First and Second dry land War were also discussed. W hat follows is a diminutive discussion on cryptography start on how cryptographic systems are sort out establish on the mathematical military operation that changes the plain text into ciphertext using the encoding get a line, based on whether a stop or catamenia cipher is produced, and based on the type of key used, whether single or two key.Substitution ciphers ciphers wherein the units of the plaintext are replaced with symbols or group of symbols, transposition ciphers rearranging of the letters of the plaintext without genuinely changing the letters themselves, dodge ciphers symmetric-key encryption algorithms that changes a fixed length block of the plaintext into the same length of cipher text, and stream ciphers also breaks plaintext into units but usually a single character are just some of the ciphers discussed in greater expatiate under the single key cryptography.A line of work in cryptography the key statistical distribution problem is also tackled. Suc h a problem usually occurs because both the sender and the receiver hold a repeat of the key, but must also interrupt others from getting access to the key. The solution to this problem, the two-key cryptography, is also discussed. Briefly, a two-key cryptography enables a substance abuser to possess two keys one mankind and one private with the public key used to encrypt the data to be sent, and the private key used to decrypt it.Some common applications of cryptography, such as protect confidential company information and defend a phone call just to name a few, are also presented. In general, the topic (Cryptography) is really well presented. At times when the topic gets a bit too technical (like algorithms), the author presents examples in order for the topic to be better understood. Such a well presented website content is quite uncommon and indeed deserves a prize. References Leary, T. (1996 July). Cryptology in the 16th and 17th Centuries.Retrieved September 27 from ht tp//home. att. net/tleary/cryptolo. htm Pell, O (nd). Cryptology. Retrieved September 27, 2007 from http//www. ridex. co. uk/ cryptology/_Toc439908875. Standaert, F-X. , Pirret, G. & Quisquater, J-J. (2003). secret writing of Block Ciphers A Survey. UCL Crypto Group proficient Report Series. Retrieved September 27, 2007 from http//www. di. ens. fr/piret/publ/cg03-2. pdf Wagner, P. (1999). Boomerang Attack. Retrieved September 27, 2007 from lasecwww. epfl. ch/intranet/proceedings-iacr-98-03/papers/1636/16360156. pdf.