Network Security English Letter Frequencies • It seems likely that cipher letters P and Z are the equivalents of plain letters e and t, but it is not certain which is which. Modular Mathemaitcs: Sometimes referred to as “clock arithmetic”, computes operations over a given range of values from 0 to N. Referred to as modulo N. One-time Pads: Offer perfect secrecy if a true source of randomness is used, but is very difficult to use in practice. Abstract: – Cryptography is the method of converting plain readable text into non-readable, and thus achieves security by it. Cryptography includes techniques such as microdots, merging words with images, and other ways to hide information in storage or transit. Rearranging or reordering the letters within a message, Monoalphabetic Cipher: Algorithm that substitutes one letter in the ciphertext alphabet for one in the plaintext alphabet. The output size is 160 bits and operates on 512-bit blocks. 5. Substitution Cipher: Replacing one letter with another, Transposition Cipher: World Jumble. This can be appended to the plaintext to be used as a MAC. secure socket layer (SSL) deprecated [2015] TLS 1.3: RFC 8846 [2018] As cryptography is the science and art of creating secret codes, cryptanalysis is the science and art of breaking those codes. Chapter 3: Block Ciphers and the Data Encryption Standard, No public clipboards found for this slide, Classical Encryption Techniques in Network Security, Student at DVR & Dr.HS MIC COLLEGE OF TECHNOLOGY. The two basic building blocks of all encryption techniques: substitution and transposition. In substitution Cipher Technique, The letter with low frequency can detect plain text. Substitution Techniques 3. login). All encryption algorithms are based on two general principles: substitution, in which each element in the plaintext (bit, letter, group of bits or letters) is mapped into another element, and transposition, in which elements in the plaintext are rearranged. The Secure Sockets Layer (SSL) protocol negotiates which asymmetric and symmetric algorithms to use in a hybrid system to protect TCP connections, such as an HTTP connection between a web browser and web server. all techniques we have studied! SHA-1 also operates on 512-bit blocks, but produces a 160-bit hash value in 4 rounds of 20 steps each. Techniques. In this case, an asymmetric encryption scheme is used to transmit a generated symmetric key to the other party, then that key is used for all further communications. Initialization Vector – Random values used with ciphers to ensure no patterns are created during encryption, Cryptosystem – The combination of algorithm, key, and key management functions used to perform cryptographic operations. For example with a shift of 1, A would be replaced by B, B would become C, and so on. The Data Encryption Standard was once a predominant symmetric-key algorithm for the encryption of electronic data. Transposition Techniques - Free download as Powerpoint Presentation (.ppt / .pptx), PDF File (.pdf), Text File (.txt) or view presentation slides online. TRANSPOSITION TECHNIQUES . Block ciphers are stronger, but slower and often implemented in hardware. • The letters S, U, O, M, and H are all of relatively high frequency and probably correspond to plain letters from the set {a, h, i, n, o, r, s}. So why do care about cryptography? Link encryption can thwart attempts at traffic analysis, although it is typically costly due to the need to have specialized routing equipment along the path. Cryptography • Cryptographic systems are characterized along three independent dimensions: – type of encryption operations used • substitution • Transposition • product – number of keys used • single-key or private • two-key or public 15. HAVAL operates on 1024-bit blocks. The combination of the two encryption methods combines the convenience of public key encryption with the speed of conventional encryption. The way in which the plaintext is processed . In cryptography (the science of writing, analyzing and deciphering codes), a substitution cipher is a method of encryption by which units of plaintext are replaced with other symbols or groups of symbols in accordance with a fixed set of rules. Lawrie Brown’s slides supplied with William Stallings ’s book “Cryptography and Network Security: Principles and Practice,” 5. th Ed, 2011. Strong encryption uses a combination of both of these attributes to attain a sufficiently complex algorithm. The most difficult problem is presented when all that is available is the ciphertext only. DSS is a US government standard and is used in e-commerce, e-mail, and financial transactions on a daily basis. Cryptography – Greek for hidden and writing is a means of transforming data in a way that renders it unreadable by anyone except the intended recipient. Steganography These slides are based on . This feature of symmetric encryption is what makes it feasible for widespread use. Polyalphabetic Cipher: Algorithm that substitutes a letter from two or more ciphertext alphabets for each plaintext alphabet letter based on position in the message. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. The history of cryptography begins where many stories of history do…. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. All substitution ciphers can be cracked by using the following tips: Scan through the […]