Stream cipher ppt

stream cipher ppt Electronic Code Book Mode The plaintext of a file encrypted as 16 DES blocks. Stream Ciphers • Generalization of one-time pad • Trade provable security for practicality • Stream cipher is initialized with short key • Key is “stretched” into long keystream • Keystream is used like a one-time pad • XOR to encrypt or decrypt • Stream cipher is a keystream generator • Usually, keystream is bits, sometimes bytes Stream Introduction to Practical Cryptography Lectures 3/4 Stream Ciphers Agenda Uses Encryption of streaming data Random bit generation Stream Ciphers Stream cipher outputs keystream, KS KS produced by a function, F, that is initialized with a key, k C = Ek(P) = P KS P = C KS k can be used only once C1 = Ek1(P1); C2 = Ek2(P2) C1 C2 = P1 KS1 P2 KS2 = P1 P2 if KS1 = KS2 Will know when P1 and P2 have RC4 Stream Cipher Algorithm for Wi-Fi Security(1) PPT FINAL - Free download as Powerpoint Presentation (. g. Yet another encrypted chat server. Generat ion o f Stream Cipher Text. Ciphertext is unreadable without knowledge of the algorithm and a Stream Cipher. CFB - Cipher Feedback (Stream Cipher) C n = P n xor E (K, C n-1) Self-Synchronising Stream Cipher. Mar 23, 2021 - Block vs Stream Ciphers - PPT, Computer, Engineering, Semester Notes | EduRev is made by best teachers of . Security. 5. Stream cipher consists of two major components: a key stream generator, and a mixing function Mixing function -is usually just an XOR function; while key stream generator is the main unit in stream About Bruce Schneier. The Advanced Encryption Standard (AES) candidate RC6 was based on RC5. The key stream is completely independent of the plaintext used. Data is encrypted and decrypted by XORing with the key stream produced by AES encrypting sequential counter block values. Dan Boneh Symmetric Ciphers: definition Def: a cipher defined over is a pair The different types of ciphers are mentioned below: Stream Cipher: i. 5. g. We now present the second class of symmetric ciphers, block ciphers. • Block vs Stream Ciphers • block ciphers process messages in blocks, each of which is then en/decrypted • like a substitution on very big characters – 64 -bits or more (these days, 128 or more) • stream ciphers process messages a bit or byte at a time when en/de -crypting • many current ciphers are block ciphers – better analysed Stream Cipher zAnother approach is generate a running key-stream and add it modulo m to the ciphertext. 1 Stream Ciphers in Practice (See Introduction to Modern Cryptography, pages 77-78). A stream cipher processes the input elements continuously, producing output one element at a time, as it goes along. , the proposed algorithm obtain solution by iteration,for realdata dependent inputs, inclusion of three feedback mechanisms are verified to provide high security level. AES-CTR uses the AES block cipher to create a stream cipher. They vary from block cipher to block cipher, as of course does the design of the algorithm itself. The codebook aspects of such systems provide confusion analogous to---though on a much grander scale---a simple substitution. 7 Block Cipher Design principles- Block Cipher modes of operations. (c) Decryption. 5. Synchronous Stream Cipher. As the name suggests, ‘addition modulus 2’ operation is performed on the plain-text to obtain a cipher-text. 2. com Chapter 2 – Stream Ciphers ver. e. 2 The Cipher Block Chaining Mode (CBC) 38 9. Synchronous Stream Ciphers n-stage Linear Feedback Shift Register: consists of n bit register r = r0…rn–1 n bit tap sequence t = t0…tn–1 Use: Use rn–1 as key bit Compute x = r0t0 … rn–1tn–1 Shift r one bit to right, dropping rn–1, x becomes r0 Operation Example 4-stage LFSR; t = 1001 r ki new bit computation new r 0010 0 01 00 Stream ciphers. It uses an infinite stream of pseudorandom bits as the key. For example, if ‘A’ is encrypted as ‘D’, for any number of occurrence in that plaintext, ‘A’ will always get encrypted to ‘D’. Unlike block ciphers, stream ciphers are easily evaluated in the forward direction to compute their output keystream and very hard to invert them. is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream (keystream). In a stream cipher (which are discussed in a previous post), the plaintext is encrypted one bit at a time. Apparently, CFB mode is converting a block cipher into a type of stream cipher. As in the OFB mode, keystream bits are created regardless of content of encrypting data blocks. 128 bits) blocks and encode each block separately. #abhics789In this video, i have explained the concept of Stream cipher and Block cipher in Cr Introduction to Modern Cryptography Lecture 2 Symmetric Encryption: Stream & Block Ciphers Stream Ciphers Start with a secret key (“seed”) Generate a keying stream i-th bit/byte of keying stream is a function of the key and the first i-1 ciphertext bits. Text is going to cryptography and network lecture ppt, it is then it with a huge collection of overhead to talk to an attack. Stream cipher with symmetric secret key. 5. Irreversible mapping Ideal Block Cipher DES Stream Cipher & Block Cipher stream cipher: encrypts data stream one bit or one byte at a time. AES An outline of Rijndael. RDP uses RSA Security's RC4 cipher, a stream cipher designed to efficiently encrypt small amounts of data. Some median performances for long messages (128-bit, 128-block size version) are: 1. Open review worked well for SSL and IPsec Summary Main functions from cryptography Public-key encryption, decryption, key generation Symmetric encryption Block ciphers, CBC Mode Stream cipher Hash functions Cryptographic hash Keyed hash for Message Authentication Code (MAC) Digital signatures Be careful Many non-intuitive properties; prefer 9. •Block cipher •Encrypts a block (string) of bits all at once. replacements * Stream Ciphers * Stream Cipher Diagram * Stream Ciphers * Stream Ciphers * The RC4 Stream Cipher Designed by Ron Rivest in 1987 for RSA Security. Cipher Block Chaining Mode Cipher block chaining. During an n-bit key setup (n is the key length), the encryption key is used to generate an encrypting variable using two arrays, state and key sign of two new stream ciphers and a thorough analysis of the algebraic immunity of Boolean functions and S-boxes based on power mappings. A stream cipher is a cryptosystem that starting from some initial parameters (seed or key) and using a certain algorithm generates a binary sequence (keystream). Do you have PowerPoint slides to share? If so, share your PPT presentation slides online with PowerShow. A syn-chronous stream cipher is a cipher where the a keystream is generated sepa-rately from the plaintext and is then combined with the plaintext later to form the Introduction to Practical Cryptography Lectures 3/4 Stream Ciphers Agenda Uses Encryption of streaming data Random bit generation Stream Ciphers Stream cipher outputs keystream, KS KS produced by a function, F, that is initialized with a key, k C = Ek(P) = P KS P = C KS k can be used only once C1 = Ek1(P1); C2 = Ek2(P2) C1 C2 = P1 KS1 P2 KS2 = P1 P2 if KS1 = KS2 Will know when P1 and P2 have Vernam cipher Cipher FeedBack (CFB) message is treated as a stream of bits added to the output of the block cipher result is feed back for next stage (hence name) standard allows any number of bits (1,8, 64 or 128 etc) to be feed back denoted CFB-1, CFB-8, CFB-64, CFB-128, etc. 7), in which the keystream (ki) is as long as the plaintext bit stream (pi). Kept as a trade secret until leaked out in 1994. Every modern cipher attempts to provide protection against ciphertext-only attacks. AES: Basic Structure- Primitive operation- Inverse Cipher- Key Expansion, Rounds, Inverse Rounds. pdf), Text File (. Modified DES algorithm is discussed in section 5. that on input 1n outputs pk, sk. Do you have PowerPoint slides to share? If so, share your PPT presentation slides online with PowerShow. Actions. Presentation Summary : Public-key encryption. modern version of a codebook cipher in effect, a block cipher algorithm yields a huge Linear feedback shift registers, Galois fields, and stream ciphers - . The major difference between a block cipher and a stream cipher is that the block cipher encrypts and decrypts a block of the text at a time. AES Creating of the state and rk arrays. Our proposed algorithm has advantages, Exploiting WEP AirSNORT Once 5-10 million packets have been gathered, < 1 second to crack WEP Crack Open source tool to exploit same RC4 vulnerabilities WPA Wi-Fi Protected Access Created to patch WEP Intended as intermediate security platform Between WEP and 802. The main difference between Block cipher and Stream cipher is that block cipher converts Converts the plain text into cipher text by taking plain text’s block at a time. Best used in hardware implementations. In stream cipher, keys and algorithm are applied to each binary digit in a data stream, one bit at a time, rather than encrypting block of data (A stream cipher operates on plaintext accepting only one bit at a time). This is the rst time that a cube attack was shown to be e ective against the full version of a well known cipher which resisted all previous attacks. It is also referred to as ‘Shift Cipher’ or ‘Caesar Cipher’. Definitions Cryptography = the science (art) of encryption Cryptanalysis = the science (art) of breaking encryption Cryptology = cryptography + cryptanalysis Cryptography Goals Encryption – Prevent Eve from intercepting message Authentication – Prevent Eve from impersonating Alice Symmetric (secret) Key Alice and Bob share a secret Symmetric Stream Cipher. “ar" encrypts as "RM" CMSC 414 Computer and Network Security Lecture 4 Jonathan Katz Announcements HW1 out Work in teams of two students Both students should contribute to all problems Material covered on HW1 is fair game for the exam Post on Piazza if you are looking for a partner Assigned reading on course syllabus Review If we want perfect secrecy, we face several inherent limitations Key as long as the message Block ciphers 5. G mi. The encryption algorithm is used as a key-stream generator to produce key-stream that is placed in the bottom register. Transmit ‘v’ and the cipher text over a radio link. Block Cipher Stream Cipher; 1: Definition: Block Cipher is the type of encryption where the conversion of plain text performed by taking its block at a time. w7 stream cipher algorithm is proposed by S. Let’s see the difference between them: Stream Ciphers 25 Correlation Attack Trudy obtains some segment of keystream from LFSR stream cipher oOf the type considered on previous slides Can assume stream cipher is the multiple shift register case oIf not, convert it to this case Stream Cipher Model Si Si+1: state of the cipher at time t = i. pdf), Text File (. pptx), PDF File (. ingredi ents of the stream cipher text. Last update: 4/4/01. A stream cipher built around LFSRs and producing one bit output on each clock = classic stream cipher design. Cipher Feedback Mode (a) Encryption. we can compute the starting part of the ciphertext before the trailing part of the plaintext is known. Block Cipher: Encrypts blocks of plaintext, treated as a whole and used to produce a ciphertext block of equal length [2]. where, C Stream Cipher Algorithm RC4 Network Security, WS 2009/10, Chapter 2. Notes on cryptography ciphers: rsa, dsa, aes, rc4, ecc. The key tenet of using stream ciphers securely is to NEVER repeat key use because of the communative property of XOR. • Stream cipher approximates OTP by using PRNG • A PRNG expands a short random seed into a long string that “looks random” • A PRNG-based stream cipher has fundamental weaknesses – same stream cannot be used twice – highly malleable Using the CTR mode makes block cipher way of working similar to a stream cipher. The Vernam Cipher is based on the principle that each plaintext character from a message is 'mixed' with one character from a key stream. ppt - Cryptography II From various sources available upon request Stream Ciphers The one-time pad is a kind of stream cipher the plaintext Unit4CryptoII. It is a variable key-size stream cipher with byte-oriented Stream CiphersStream Ciphers • A stream cipher is a type of symmetric encryption in which input data is encrypted one bit (sometime one byte) at a time • Examples of stream ciphers include SEAL, TWOPRIME, RC4, A5 Encryption Plaintext bits Ciphertext bits Keystream bits 4. 0 GetBits takes the current state st and outputs a bit y along with updated state st’ In practice, y would be a block rather than a bit Stream ciphers - encrypt one bit or character or symbol of plaintext into bit or symbol of Ciphertext at a time e. DOWNLOAD Module-2 IDEA: Primitive operations- Key expansions- One round, Odd round, Even Round- Inverse keys for decryption. In other words, the key stream is considered as a predetermined stream of keys or K = (k, k, …, k). Unlike a modern stream cipher (such as those in eSTREAM), RC4 does not take a separate nonce alongside the key. The Vigenère cipher is an example of a stream cipher. Lightweight stream ciphers Talking about flow algorithms, it can be said that they are good for encrypting large amounts of data. 96 cpb on a Broadcom BCM2836 block cipher. The encrypted data. We again RC4 is a stream cipher and variable length key algorithm. diffusion Block ciphers encrypt a group of plaintext symbols as one block e. The definition of PPT, a method for generating the PPTs, properties of PPT are presented in section 3. View Stream Cipher And Block Ciphers PPTs online, safely and virus-free! Many are downloadable. Rc4 encryption in c# bitlush. By stream cipher, we refer to the algorithm that generates the stream (i. In the ideal case, a one-time pad version of the Vernam cipher would be used (Figure 2. If C 1 and C 2 have been XOR'd with a key K, retrieving that key K is trivial because C 1 XOR C 2 = P 1 XOR P 2 and having an english language based XOR means that cryptoanalysis tools such as a character frequency analysis will work Title: streamkil. Stream cipher is also known as Stream and Block Ciphers: Stream Cipher: Encrypts a digital data stream one byte at a time [2]. 2 Types of Stream Ciphers In [1], an interesting distinction is made between two types of stream ciphers { synchronous stream ciphers and self-synchronizing stream ciphers. t. Learn new and interesting things. zi = f(zi−1, zi−2, , zi−t, k), yi = g(xi, zi). area and many interesting new stream ciphers have been proposed and analyzed. Say we want to encrypt single bits at the type. A stream cipher on the other hand processes . Pseudorandom number generation using a block cipher 4. A key input is pseudorandom bit generator that produces a stream 8-bit number that is unpredictable without knowledge of input key, The output of the generator is called key-stream, is combined one byte at a time with the plaintext stream cipher using X-OR operation. Key length: up to 2048 bits; RC4 is a symmetric stream cipher, known and praised for its speed and simplicity. Usage. Stream cipher encrypts one character at a time and decrypts one character one at time. In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream. ppt - Free download as Powerpoint Presentation (. In this scheme, the plaintext is processed one bit at a time i. g. In cryptography, a transposition cipher is methods of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the cipher text constitutes a permutation of the plaintext. First we present WG, a family of new stream ciphers designed to obtain a Evaluating Stream Ciphers A simple way to encrypt long/infinite streams of data (e. Block Ciphers •Stream cipher •Encrypts a message bit by bit (stream of bits). Stream ciphers Keystream XOR operation Linear feedback Nonlinear feedback Stop-and-go generator Shrinking generator Block ciphers Fixed length Feistel cipher Rounding functions DES AES Substitution-permutation network Asymmetric Key aka Public key William Joven Diffie-hellman RSA MIT UK Diffie Joven Hellman Logic Piano Cryptanalysis A stream cipher is one that encrypts a digital data stream one bit or one byte at a time. e. Lecture 2 symmetric encryption, stream ciphers, block ciphers. G : output function. For each key K ∈{0,1}k we let E K: {0,1}l →{0,1}l be the function defined by E K(M)=E(K,M). Rc4 cryptoapi encryption password verification – microsoft open. Rc4&rc5. Understanding Cryptography – A Textbook for Students and Practitioners by Christof Paar and JanPelzl www. com. In a stream cipher the plaintext digits are encrypted one at a time, and the transformation of successive digits varies during the encryption. the input elements one bit at a time continuously, to produce . With a 128 bits key, the period is gt 10100 . The encryption key for the ideal block cipher is the codebook itself, meaning the table that shows the relationship between the input blocks and the output blocks. (b) Decryption. There are five types of operations in block cipher modes, ECB (Electronic Code Block) mode, CBC (Cipher Block Chaining) mode, CFB (Cipher Feedback) mode, OFB (Output Feedback) mode and CTR ( Counter) mode. A generalization of Caesar’s cipher is Vigenère’s cipher: It was invented several times, nowa-days the reference goes back to the French cryptographer Blaise de Vigenère. Symmetric Cryptography 7-18 Times New Roman MS PGothic Arial Wingdings Calibri Tahoma Kendall Master 2007 2_Kendall Master 2007 ThemePowerPoint1 1_Kendall Master 2007 1_ThemePowerPoint1 2_ThemePowerPoint1 CHƯƠNG 2 MÃ HÓA ĐỐI XỨNG HIỆN ĐẠI NỘI DUNG Mã dòng (Stream Cipher) Mã dòng (Stream Cipher) Mã dòng (Stream Cipher) A5/1 Mã dòng (Stream Cipher ECB – Electronic Code Book mode Divide plaintext into blocks Encrypt each block independently, with same key CBC – Cipher Block Chaining XOR each block with encryption of previous block Use initialization vector IV for first block OFB – Output Feedback Mode Iterate encryption of IV to produce stream cipher CFB – Cipher Feedback Mode The Vernam Cipher is based on the principle that each plaintext character from a message is 'mixed' with one character from a key stream. Modern block ciphers employ both confusion and diffusion. 5 The Counter Mode (CTR) 45 9. Stream, Block Ciphers • E encipherment function – E k (b) encipherment of message b with key k – In what follows, m = b 1 b 2 …, each b i of fixed length • Block cipher – E k (m) = E k (b 1)E k (b 2) … • Stream cipher – k = k 1 k 2 … – E k (m) = E k1 (b 1)E k2 (b 2) … – If k 1 k 2 … repeats itself, cipher is periodic plaintext encrypted two letters at a time: if a pair is a repeated letter, insert a filler like 'X', eg. block ciphers. g. Formal Definition of a Stream Cipher Let E be an encipherment algorithm, and let Ek(b) be the encipherment of the message b with key k. Substitution Algorithms are (Stream): Cesar Cipher Simple Key Substitution Monoalphabetic Cipher (Affine Cipher) Playfair Cipher Polyalphabetic Cipher (vigenere Cipher) Polyalphabetic Cipher (Vernam Cipher) One-Time Pad Transposition Algorithms are (Stream): Rail fence technique 2D matrix (One or more transpositions) Scytail Rotor Machines (Enigma) C. The Adobe Flash plugin is needed to view this content. Selcuk Stream Ciphers * Attacks on WEP (cont’d) An active attack: Since RC4 is a stream cipher, an attacker can modify the plaintext bits over the ciphertext and fix the CRC checksum accordingly. Implementation of RC4 cipher wasn't known until September 1994 when it was anonymously posted to the Cypherpunks mailing list. The finalists of the competition were announced in 2008 and included three stream ciphers for hardware applications with restricted resources: • Grain is widely analyzed and provides implementation flexibility, and also has a version that supports authentication. GetBits takes as input 𝑠𝑡𝑖and outputs a bit 𝑦 and state 𝑠𝑡𝑖+1. Attacking Substitution Ciphers with Genetic Algorithms Two Varieties of Secure Sockets The NitNat Cipher Solved! Invent your own Stream Cipher!? Persecution of Crypto Hacker. CCMP achieves confidentiality in counter mode by taking each of consecutive 128 bit blocks of packet plaintext and XORing it with a keystream formed from encryption of a counter, incremented for each block, using Stream Ciphers are fast and easy to implement in hardware. In order to improve the time-data-memory tradeoff for stream cipher, a concept of Hellman’s time-memory tradeoff [4] has been applied and it We demonstrate a 4,294,967,296-quadrature amplitude modulation (QAM) based Y-00 quantum stream cipher system carrying a 160-Gb/s 16-QAM signal transmitted over 320-km SSMF. A stream cipher can be constructed with any cryptographically strong PRNG. 7), in which the keystream (k ) is as long as the plaintext bit stream (p). Symmetric algorithms. 1 we talked about block ciphers, now we will talk about other class of ciphers the stream ciphers. A stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream (keystream). A stream cipher is one that encrypts a digital data stream one bit or one byte at a time. dvi Created Date: 1/11/2007 5:35:43 PM Unit4CryptoII. g. 4 A stream cipher . To officially take the course, including homeworks, projects, and final exam, please visit the course page at Coursera. Rc4 encryption algorithm. 3 The Cipher Feedback Mode (CFB) 40 9. It is a structure on which many ciphers such as the Lucifer cipher are based. If P n is less than 64-bits, e. Introduction Originate from one-time pad bit-by-bit Exor with pt and key stream (c i = m i z i ) Encryption = Decryption --&gt; Symmetric Slideshow Stream Ciphers Generalization of one-time pad Trade provable security for practicality Stream cipher is initialized with short key Key is “stretched” into long keystream Keystream is used like a one-time pad XOR to encrypt or decrypt Stream cipher is a keystream generator Usually, keystream is bits, sometimes bytes Stream Cipher Generic view of stream cipher Stream Cipher We consider 3 real stream ciphers ORYX — weak cipher, uses shift registers, generates 1 byte/step RC4 — strong A stream cipher can be constructed with any cryptographically strong PRNG. Stream Ciphers Stream Ciphers 1. a stream cipher. Therefore, stream ciphers will be a hot topic and attract lots of research attention in the coming years. Used in the SSL/TLS standards Definition 1. Now customize the name of a clipboard to store your clips. com. One bit at a time is considered for encryption and decryption in stream cipher. Scribd is the world's largest social reading and publishing site. 1 30 The Data Encryption Standard (DES) – History 1973 the National Bureau of Standards (NBS, now National Institute of Standards and Technology, NIST) issued a request for proposals for a national cipher standard, demanding the algorithm to: provide a high level of security, Introduction to Cryptography Matt Mahoney Florida Tech. edu is a platform for academics to share research papers. RC4 is designed for secure communications over networks. I've been writing about security issues on my blog since 2004, and in my monthly newsletter since 1998. A stream cipher can be constructed with any cryptographically strong PRNG. ppt / . This cipher is sometimes called ashift cipher and sometimes Caesar cipher, but the term additive cipher better reveals its mathematical nature. The process of selecting a new cipher design standard usually takes many years and includes exhaustive testing of large quantities of ciphertext for any statistical different approach from random noise. Security of stream cipher depends entirely on details of keystream generator. Block Ciphers • Map n-bit plaintext blocks to n-bit ciphertext blocks (n = block length). , 128-bit seed into a 106-bit pseudo-random sequence No efficient algorithm can tell this sequence from truly random Block ciphers tend to encrypt a block of characters of a plaintext message using a fixed encryption transformation A stream cipher encrypt individual characters of the plaintext using an encryption transformation that varies with time. Course Contents: Major Sections and Topics Key Definitions Problems Misordered blocks, code book mode; Stream and Block Ciphers Block cipher, stream cipher, LFSR, tap sequence, NLFSR, output feedback mode, counter method, self-synchronous stream ciphers, autokey, cipher feedback mode, self-healing property, multiple encryption, EDE mode, triple In cryptography, RC5 is a symmetric-key block cipher notable for its simplicity. Stream Ciphers 1. This means A5/1 is a stream cipher used to provide over-the-air communication privacy in the GSM cellular telephone standard. Stream Cipher. Ciphertext is typically the output of an encryption algorithm operating on plaintext. C = (M + k) mod n M = (C – k) mod n. Additive Cipher (Shift Cipher / Caesar Cipher) – The simplest mono-alphabetic cipher is additive cipher. A cipher is a message that has been transformed into a nonhuman readable format. That state change is controlled by the key, and, in some stream ciphers, by the plaintext stream as well. e. than extrapolated from smaller variants of the cipher. The counterpart of block cypher is the stream cypher, which operates on its input one bit at a time, also using a shared key. Each block of 4 bits in the plaintext is transformed into a block of 4 ciphertext bits. It uses a variable length key from 1 to 256 bit to initialize a 256-bit state table. Stream cipher operates by expanding a short key into an infinite pseudo-random key stream. It is interesting to note that whilst there are proven architectures for Feistel compression functions and indeed native block ciphers like substitution and permutationthere are no equivalent standardised architectures for a key schedule. All of these algorithms require initialization period, where the development of the internal state is done in the idle (there is no encryption). Looking ahead: Stream Ciphers vs. g. , a network link). ppt - Free download as Powerpoint Presentation (. While stream cipher Converts the plain text into cipher text by taking 1 byte of plain text at a time. The principal difference between this two types of ciphers is in block ciphers we cipher a block of data per time and in stream ciphers we cipher a stream of data. Key-stream is independent of plain chapter-3-symmetric-key-crypto-stream-ciphers-block-ciphers-block-cipher. This method of encryption uses an infinite number of pseudorandom cipher digits per key. 2 Stream Ciphers In the subsection 2. 5 Five Modes of Operation for Block Ciphers 24 9. Assume that the plain text consists of lowercase letters and ciphertext of uppercase letters. Administrators can choose to encrypt data by using a 56- or 128-bit key. 1 Introduction to block ciphers In the previous chapter we have been introduced to stream ciphers. Stream Cipher Vulnerabilities¶ Key Reuse¶. 99 cycles per byte (cpb) on an AMD Ryzen 7 1700; 1. Download ppt “Feistel Cipher Structure”. Cryptology combines the techniques of both cryptography and cryptanalyst. In this mode, subsequent values of an increasing counter are added to a nonce value (the nonce means a number that is unique: number used once ) and the results are Study Guide for Week #07 Cipher Techniques. Caesar cipher is an example Stream Cipher: A stream cipher is a method of encryption where a pseudorandom cipher digit stream is combined with plain text digits. • For n-bit plaintext and ciphertext blocks and a fixed key, the encryption function is a bijection; • E : Pnx K → Cns. F : state function. Thomas, PRG G is a PRG if {G k(x)} x←{0,1}k ≈ U n(k) and G PPT A PRG can be used to obtain a one-time CPA-secure SKE Stream cipher: PRG without an a priori bound n(k) on the output length In today’s age of computers cryptography is often associated with the process where an ordinary plain text is converted to cipher text which is the text made such that intended receiver of the text can only decode it and hence this process is known as encryption. g if 8 bits, use top 8 bits of C n, and shift into bottom 8 bits of input to E (input is a 64-bit shift register). A stream cipher is one that encrypts a digital data stream one bit or one byte at a time. Andreas Steffen’s Security Tutorial Cryptography Symmetric-Key Cryptography Cryptanalysis Cryptanalysis (2) Examples Simple and non-secure ciphers Shift Cipher – Caesar Cipher Affine Cipher Vigenere Cipher Hill Cipher Information-secure cipher One-Time Pad Confusion and Diffusion Confusion and ChaCha20 stream cipher in C. Simple and fast. Instructor: Dan Boneh, Stanford University Online cryptography course preview: This page contains all the lectures in the free cryptography course. PPT – Stream Ciphers PowerPoint presentation | free to view - id: 152f57-YTU1O. 2. Self-Synchronizing Stream Ciphers Synchronous Stream Ciphers. In this mode, subsequent values of an increasing counter are added to a nonce value (the nonce means a number that is unique: number used once ) and the results are cipher. mike thomsen cryptography ii may 14 th , 2012. zNote: Adding two plaintexts together is not good enough, the key-stream needs to be more random than that. • Combine the stream with the plaintext to produce the ciphertext (typically by XOR) = ⊕ Example of Stream Encryption Key Ciphertext Stream View Traditional_Block_cipher-1. CMSC 414 Computer and Network Security Lecture 4 Jonathan Katz HW1 out Randomized encryption Deterministic encryption schemes cannot be secure against chosen-plaintext attacks Nor can they be secure for encrypting multiple messages To be secure against chosen-plaintext attack, encryption must be randomized Moral: always use randomized encryption! stream cipher. By stream cipher, we refer to the algorithm that generates the stream (i. ) (a). The most popular stream cipher. the pseudorandom generator G). •Hv ufe fh kar karvedrh vu pfkarpfkdlh fer fivnk erfmdkz, karz fer svk lrekfds; hv ufe fh karz fer lrekfds, karz fer svk fivnk erfmdkz. Th e key st ream gene rated fro m the b ank of LFSRs a nd the e ncoded v ersion of the Engl ish test is the major tw o . for all key k ∈K, E(x, k) is an invertible mapping, written Ek(x). Generate a pseudo-random key stream & xor to the plaintext. Designed by Ron Rivest of RSA Security in 1987. 6 Stream Ciphers 49 9. With a Stream Cipher, the same plaintext bit or byte will encrypt to a different bit or byte every time it is encrypted. 5. Key: The seed of the PRNG Slideshow 3107395 by dale Stream Ciphers - PowerPoint PPT Stream Ciphers Stream ciphers, like block ciphers, break message into fixed length blocks, but use a sequence of keys to encrypt the blocks. Have a family-key variant to allow for di er-ent, non-interoperable, versions of the cipher. Introduction Pseudorandomness LFSR Design Refer to “Handbook of Applied Cryptography” [Ch 5 & 6]. This pseudorandom cipher digit stream is applied to each binary digit, one bit at a time. ppt), PDF File (. Block cipher Motivation Reversible vs. Fig: CBC encryption and decryption block diagram CFB (Cipher Feedback) A close relative of CBC. A number of serious weaknesses in the cipher have been identified. 3; Homework 1 Assigned: Week 3 (Jan 23 -- Jan 27) CPA Security; Slides ppt; Katz and Lindell: 3. : Caesar shift cipher (one letter at time) XOR-scheme (one bit at a time) block cipher: a block of plaintext is Cipher IV Block Cipher Block Cipher Block Cipher Advantages: Identical blocks encrypted differently Last ciphertext block depends on entire input Comparison (for AES, by Bart Preneel) Similar plaintext blocks produce similar ciphertext (see outline of head) No apparent pattern RC4 stream cipher – “Ron’s Code” uDesign goals (Ron Rivest The First Type Symmetric key ciphers use the same key for encryption and decryption "private-key", "one-key" and "single-key" cryptography block ciphers and stream ciphers Drawback: Key must be shared in a non-traditional communication medium else the key and encrypted data can be collected & decrypted by anyone Stream Cipher Encrypts bit-per RC4 is a stream cipher, symmetric key algorithm. The main difference is that instead of using only one k 2 Z, we now use k 2 Zn for some n 2 N. g. 1 Introduction Chapter 3 – Block Ciphers and the Data Encryption Standard 1 Modern Block Ciphers will now look at modern block ciphers one of the most widely used types of cryptographic algorithms provide secrecy and/or authentication services in particular will introduce DES (Data Encryption Standard) We will look at AES (Advanced Encryption Standard) adopted in 2001 later Block vs Stream Ciphers block A stream cipher is simply a weaker version of a one-time pad and hence stream ciphers employ only confusion. Information Security and Cryptography - Vernam (Stream) Cipher Stream ciphers The One Time Pad Online Cryptography Course Dan Boneh . txt) or view presentation slides online. What is the difference between Stream Cipher Stream cipher as the name suggests each character is being replaced from the plain text. Adams Block Ciphers - . Additive cipher: The simplest mono-alphabetic cipher is the additive cipher. Introduction Pseudorandomness LFSR Design Refer to “Handbook of Applied Cryptography” [Ch 5 & 6]. Stream ciphers, in contrast to the 'block' type, create an arbitrarily Additive ciphers can be categorized as stream ciphers in which the key stream is the repeated value of the key. (b) Decryption. 5-2 MODERN STREAM CIPHERS In a modern stream cipher, encryption and decryption are done r bits at a time. AES-CTR also supports key stream precomputation. Stream algorithms have keystroke generators. one bit of plaintext is taken, and a series of operations is performed on it to generate one bit of ciphertext. crypto-textbook. Introduction to Symmetric Block Cipher Jing Deng Based on Prof. A block cipher is one in which a block of plaintext is treated as a whole and used to produce a ciphertext block of equal length. Initial state, output and state functions are controlled by the secret key. Designed by Ronald Rivest in 1994, RC stands for "Rivest Cipher", or alternatively, "Ron's Code" (compare RC2 and RC4). Stream Ciphers and Block Ciphers Symmetric encryption algorithms are traditionally divided into two categories: stream ciphers and block ciphers. It is a symmetric key algorithm supporting key lengths of 128 bits. ppt from COMP 3350 at University of Manitoba. Figure 1 depicts an ideal block cipher that uses blocks of size 4. The ultra-dense QAM cipher template is realized by an integrated two-segment silicon photonics I/Q modulator. A Feistel cipher is a multi-round cipher that divides the current internal state of the cipher into two parts and operates only on a single part in each round of encryption or decryption. Get the plugin now. vided into block ciphers and stream ciphers. Designed by Ron Rivest in 1987 for RSA Security. 1 bit) Stream Cipher ZUC: InitializationStream Cipher ZUC: Initialization • Load 128-bit key & 128-bit IV into register • Run the cipher for 32 stepsRun the cipher for 32 steps – Each 32-bit keystream is truncated to 31 bits – ThThen XOR dXORed to S 15 (l fh i)(one e lement o f the reg ister ) • Ready for keystream generation 5 Vignere cipher etc. This page is maintained by CB. The process of conversion of cipher text to plain text this is known as decryption. An algorithm that operates on fixed-length blocks of data, one block at a time, rather than encrypting one bit at a time as in stream ciphers. 2: Conversion of Bits In contrast to RC4 of WEP which is a stream cipher, AES is a block cipher, although it does use a key stream to encrypt each block. Stream Ciphers Generalization of one-time pad Trade provable security for practicality Stream cipher is initialized with short key Key is “stretched” into long keystream Keystream is used like a one-time pad XOR to encrypt or decrypt Stream cipher is a keystream generator Usually, keystream is bits, sometimes bytes Stream Cipher Generic view of stream cipher Stream Cipher We consider 3 Security Requirement for wireless Network SECURITY GOALS-STREAM CIPHER Stream cipher functions on a stream of data by operating on it bit by bit. ppt), PDF File (. In this case we find some linear expression L1 including only symbols from the output stream of the “linearized” cipher (the linear cipher without noise variables), which is always equal to a constant (usually equal to 0). Stream Cipher 5. Contribute to shiffthq/chacha20 development by creating an account on GitHub. A Public-key Encryption Scheme Is Composed Of Three Ppt PPT. Become a clipboard to cryptography network security lecture notes, free account is denoted by disabling the author has to make this is an absence. Deciphering is reversing a cipher into the original text. The encoding of each block generally depends on at most one of the previous blocks. As in the OFB mode, keystream bits are created regardless of content of encrypting data blocks. Stream Cipher Types. A block cipher enciphers input in blocks of plaintext as opposed to individual characters, the input form used by a stream cipher. "balloon" encrypts as "ba lx lo on" if both letters fall in the same row, replace each with letter to right (wrapping back to start from end), eg. But traditionally stream cipher systems (as CFB makes a block cipher into a stream cipher, a self-synchronising one) work on bits or bytes, so NIST also standardised a variant of CFB that allows that, and generalises CFB for whole blocks. It contains eight similar models, C1, C2, …, C8 where C2 is illustrated as follows. What are the two general approaches to attacking a cipher? Cryptanalysis and brute force. 0, and SCREAM [16]. Idea of a stream cipher: partition the text into small (e. Stream cipher - symmetric cipher where plaintext bits are combined with a pseudo random cipher bit stream (keystream), typically by an exclusive or (xor) operation. , 64 or 128 bits), and encrypts each of them independently using the same key-dependent transforma-tion. The most popular stream cipher. Where ECB and CBC mode works on block ciphers, and CFB and OFB mode works on block ciphers acting as stream ciphers. Stream Cipher. Even though AES is a block cipher and RC4 is a stream cipher, TLS can implement either one. (a) Encryption. zThis is similar to the idea of the Vigenère cipher, except that the period (if any) is made very long. Block ciphers are stronger, but slower and often implemented in hardware. 1X authentication server Feistel cipher is not one particular cipher. 1 bit → CFB1 8-bits → CFB8 64-bits → CFB64 P1 P2 Vernam cipher Cipher FeedBack (CFB) message is treated as a stream of bits added to the output of the block cipher result is feed back for next stage (hence name) standard allows any number of bits (1,8, 64 or 128 etc) to be feed back denoted CFB-1, CFB-8, CFB-64, CFB-128, etc. Block Cipher and Stream Cipher are the methods used for converting the plain text into cipher text directly and belong to the family of symmetric key ciphers. A stream cipher is a function which directly maps k -bit keys and arbitrary length plaintexts to (same arbitrary length) ciphertext, in such a way that prefixes of the plaintext map to prefixes of the ciphertext, i. According to ECRYPT's stream cipher benchmarks (eBASC), Speck is one of the fastest ciphers available, both for long as well as short messages. A stream cipher operates on the plaintext symbol by symbol to produce a sequence of cipher symbols from an alphabet c#. Scribd is the world's largest social reading and publishing site. This is due to the fact that encryption is carried out by first generating a stream of pseudorandom bits, and then XORing this stream with the plaintext. 27 cpb on an Intel Core i5-6600; 15. A stream cipher processes the input elements continuously, producing output one element at a time, as it goes along. How WEP Works How WEP works ? WEP uses RC4 encryption algorithm known as “stream cipher” to protect the confidentiality of its data. ((d and d are frequently the same. The algorithm is based on the use of a random permutation. This is animation of the principle of A5/1 stream cipher used to provide over-the-air communication privacy in the GSM cellular telephone standard. In that case the cipher is similar to the unbreakable One-Time Pad (OTP). Introduction Originate from one-time pad bit-by-bit Exor with pt and key stream (c i = m i z i ) Encryption = Decryption --&gt; Symmetric Slideshow Stream Ciphers A stream cipher is a deterministic algorithm (Init, GetBits) where, Init takes as input a seed 𝑠 and an optional initialization vector 𝐼𝑉 and outputs a state 𝑠𝑡0. Only need to send 8-bit values in this case. It is one of seven algorithms which were specified for GSM use. XOR is short for exclusive OR. Rick Han’s Lecture Slides Dr. g. In the ideal case, a one-time pad version of the Vernam cipher would be used (Figure 2. e. The RC4 stream cipher works in two phases, key setup and ciphering. ppt - Cryptography II From various sources Pseudorandomness and Stream Ciphers ; Slides ppt; Katz and Lindell: 3. Monoalphabetic ciphers •Our examples of the permutation, shift, decimation, and affine ciphers were monoalphabetic ciphers, that is every letter was replaced by the same letter each time. – Fmirek Rdshkrds. 7. 5. Bits are X-ORed with a bit from message. •Inherently stateful; needs to keep track of the location of last encrypted bit. This algorithm encrypts one byte at a time (or larger units on a time). columnar transposition Stream Ciphers and Block Ciphers stream cipher A symmetric encryption algorithm in which ciphertext output is produced bit-by-bit or byte-by-byte from a stream of plaintext input. Bandwidth reduction features Cipher IV Block Cipher Block Cipher Block Cipher Advantages: Identical blocks encrypted differently Last ciphertext block depends on entire input Comparison (for AES, by Bart Preneel) Similar plaintext blocks produce similar ciphertext (see outline of head) No apparent pattern RC4 stream cipher – “Ron’s Code” uDesign goals (Ron Rivest and then XORing this stream with the plaintext. •Can be stateless or stateful شرح كامل للتشفير و فك التشفير عن طريق Vernam (Stream) Cipher بطريقة مبسطة مع حل مثال. For example, let the secret be represented by the word SECRET. CS470, A. Cryptanalysis is the art of deciphering ciphers without the knowledge of the key used to cipher them. Second, use the XORed data as input for Blowfish's or stream ciphers [7]. (a) Encryption. It was initially kept secret, but became public knowledge through leaks and reverse engineering. * RC4 is a stream cipher designed in 1987 by Ron Rivest for RSA Security. In that case the cipher is similar to the unbreakable One-Time Pad (OTP). most efficient to use all bits in block (64 or 128) Ci = Pi XOR EK View UNIT-2-2. We feel we have met all of these goals in the design of Two sh. ci. 4 The Output Feedback Mode (OFB) 43 9. Cryptanalysis and Brute-Force Attack Typically, the objective of attacking an encryption system is to recover the key in use rather than simply to recover the plaintext of a single ciphertext. And we believe that in the near future, there will be some standardized stream cipher that is widely used just as AES for block ciphers. It is one You just clipped your first slide! Clipping is a handy way to collect important slides you want to go back to later. Basic Principles 📚📚📚📚📚📚📚📚GOOD NEWS FOR COMPUTER ENGINEERSINTRODUCING 5 MINUTES ENGINEERING 🎓🎓🎓🎓🎓🎓🎓🎓SUBJECT :-Discrete Mathematics (DM) Theory Of Computation ( XOR <M,c(M)> with the key stream to get the cipher text. This means that if a single long-term key is to be used to securely encrypt multiple streams, the protocol must specify how to combine the nonce and the long-term key to generate the stream key for RC4. * RC4 is a stream cipher designed in 1987 by Ron Rivest for RSA Security. What is a stream cipher? A stream cipher is an encryption algorithm that encrypts 1 bit or byte of plaintext at a time. g. The transformation is controlled by a secret key K, and it is written EK(x)=y The decryption algorithm of the underlying block cipher is never used. In this cipher, however, each character in the ciphertext depends only on the corresponding character in the plaintext, because the CMSC 414 Computer and Network Security Lecture 5 Jonathan Katz Announcements Midterm on March 15 Modes of encryption Used for encrypting a long message m1, …, mn ECB Ci = FK(mi); the ciphertext is (C1, …, Cn) CBC IV; Ci = FK(mi Ci-1); the ciphertext is (IV, C1, …, Cn) OFB (stream cipher mode) IV; zi = FK(zi-1); Ci = zi mi; the ciphertext is (IV, C1, …, Cn) CTR (stream cipher mode) IV ICS 454: Principles of Cryptography Block Ciphers & DES Sultan Almuhammadi Outline Stream cipher vs. A public-key encryption scheme is composed of three PPT algorithms: Gen: key-generation algorithm. One-Time Pads stream cipher works in t wo phases, key setup and cipheri ng. Stream cipher consists of two major components: a key stream generator, and a mixing function Mixing function -is usually just an XOR function; while key stream generator is the main unit in stream with a Stream-Cipher One-time Encryption with a stream-cipher: Generate a one-time pad from a short seed Can share just the seed as the key Mask message with the pseudorandom pad Decryption is symmetric: plaintext & ciphertext inte rchanged SC can spit out bits on demand, so the message can arrive bit by After approximation, all operations in the “linearized” part of the cipher are linear. 4; Monoalphabetic cipher is a substitution cipher in which for a given key, the cipher alphabet for each plain alphabet is fixed throughout the encryption process. 2. pdf), Text File (. txt) or view presentation slides online. It is a variable key-size stream cipher with byte-oriented operations. most efficient to use all bits in block (64 or 128) Ci = Pi XOR EK An introduction to stream ciphers and block ciphers. A block cipher encrypts a block of plaintext bits x to a block of ciphertext bits y. STREAM CIPHERS With one-time pad, Ciphertext(Key,Message)=Message Key Key must be a random bit sequence as long as message Idea: replace “random” with “pseudo-random” Encrypt with pseudo-random number generator (PRNG) PRNG takes a short, truly random secret seed and expands it into a long “random-looking” sequence E. Stream cipher Idea of a block cipher: partition the text into relatively large (e. Stream Cipher. 7 The RC4 Stream Cipher Algorithm 53 9. This document is highly rated by students and has been viewed 218 times. The following is a table that defines XOR (you can think of column a as a bit of plain text and column b as its corresponding key bit): a b a XOR b In a stream cipher structure, a key is input to a pseudorandom bit generator that produces a stream of 8-bit numbers that are apparently random. Stream Cipher –RC4. Kept as a trade secret until leaked out in 1994. DOWNLOAD Start with an 8-cell CA with null boundaries That is, each end is connected to 0 instead of each other Key Space: other transformation patterns For a CA Block Cipher, the key space is the space of fundamental transformations For the example on the previous slide other possible transformation patterns include: (195, 195, 195, 195, 51, 51, 51, 51 ciphers entry. the output element. With a 128 bits key, the period is > 10100 . The computer which only understands certain languages must be used to implement this transposition cipher, hence the use of a compiler Using the CTR mode makes block cipher way of working similar to a stream cipher. Technically, stream ciphers are block ciphers with a block size of one bit. Block vs. The PowerPoint PPT presentation: "RC4-Stream Ciphers Blowfish, RC5 Block Ciphers" is the property of its rightful owner. RC4 is designed for secure communications over networks. Si. The general opinion seems Hello friends! Welcome to my channel. Stream Cipher Terminology!Seed of pseudo-random generator often consists of initialization vector (IV) and key •IV is usually sent with the ciphertext •The key is a secret known only to the sender and the recipient, not sent with the ciphertext!The pseudo-random bit stream produced by PRNG(IV,key) is referred to as keystream stream cipher text and ppt with our secret key. Simple and fast. , the upper-layer protocol headers). pptx from CSE 123 at Anna University, Chennai. Block cipher and Data Encryption Standard 1 Modern Stream Ciphers In a modern stream cipher, encryption and (b) Stream Cipher 1 Figure 1. ciphertext. 2. Be suitable as a stream cipher, one-way hash function, MAC, and pseudo-random number generator, using well-understood construction methods. Cryptanalysis and Brute-Force Attack Typically, the objective of attacking an encryption system is to recover the key in use rather than simply to recover the plaintext of a single ciphertext. 1 Feistel Networks Cryptography Public-key Encryption. transposition cipher- to encrypt and decrypt message through the use of a means not yet used when the algorithm was developed the cryptosystem to be used in a computer. Get ideas for your own presentations. the pseudorandom generator G). ki. RC4 is an example of a well-known, and widely used, stream cipher; see Category:Stream ciphers. A block cipher divides the plaintext into separate blocks of fixed size (e. txt) or view presentation slides online. Since block ciphers can be turned into stream ciphers, using OFB or CFB mode, there has been some debate whether stream ciphers are useful at all. AES-CTR is easy to implement, and AES-CTR can be pipelined and parallelized. Blowfish and Twofish Blowfish is a strong symmetric block cipher that is still widely used today. 8 WEP, WPA, and WPA2 FOR WiFi TKIP uses the RC4 stream cipher as the encryption and decryption algorithm and all involved parties must share the same secret key. In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream. • the same“key”is used at each block. CS259 Winter 2008 Cryptography Overview John Mitchell Iterated hash functions Repeat use of block cipher or custom function Pad input to some multiple of block length Iterate a length-reducing function f f : 22k -> 2k reduces bits by 2 Repeat h0= some seed hi+1 = f(hi, xi) Some final function g completes calculation Pad to x=x1x2 …xk f g xi f(xi-1) x Applications of one-way hash Password Types of symmetric encryption Stream ciphers – pseudo-random pad Generate pseudo-random stream of bits from short key Encrypt/decrypt by XORing as with one-time pad But NOT one-time PAD! (People who claim so are frauds!) RDP uses RSA Security's RC4 cipher, a stream cipher designed to efficiently encrypt small amounts of data. This key stream is then XORed with the plaintext as in case of stream cipher. block cipher A symmetric encryption algorithm in which a block of plaintext bits (typically 64 or 128) is transformed as a whole into a ciphertext block of the same length. Stream & Block Ciphers Stream Ciphers • Start with a secret key (“seed”) • Generate a keying stream • i-th bit/byte of keying stream is a function of the key and the first i-1 ciphertext bits. Overview of the Feistel Network. An illustration of encryption process using DES with PPT’s based key is with a Stream-Cipher One-time Encryption with a stream-cipher: Generate a one-time pad from a short seed Can share just the seed as the key Mask message with the pseudorandom pad Decryption is symmetric: plaintext & ciphertext inte rchanged SC can spit out bits on demand, so the message can arrive bit by Stream Ciphers. The primary advantage of a stream cipher is that stream ciphers are almost always faster and use far less code than do block ciphers. 2. Stream Ciphers. Hash functions are also a type of . It is a variable key-size stream cipher with byte-oriented • a proprietary cipher owned by RSA DSI • a Ron Rivest design, simple but effective • variable key size, byte -oriented stream cipher • was widely used (web SSL/TLS, wireless WEP/WPA) • key forms random permutation of all 8 -bit values • uses that permutation to scramble input info processed a byte at a time • these days, known to have vulnerabilities new stream ciphers that might be suitable for widespread adoption. . Encrypts individual bits of the message. Enc: Well-known implementations of the block cipher algorithm are the Data Encryption Standard (DES), TripleDES and the Advanced Encryption standard (AES). This keystream is XORed with the plaintext in order to generate the ciphertext. Share buttons are a little bit lower. • The inverse mapping is the decryption function, RC4 – user provides a key, the key is used to create a pseudo-random string of bits that are then XOR’d with plaintext for the cipher text CRC-32 (cyclic redundancy check ) – same system used for DVDs and CDs In general terms, a mathematical formula is created for a specific stream of text and appended to the string, after the text In a stream cipher, the output stream is created based on an internal state which changes as the cipher operates. Stream Cipher Mode A stream cipher. In a block cipher, the plaintext is broken into blocks of a set length and the bits in each block are encrypted together. October 29, 2009 These slides were prepared by Thomas Eisenbarth, Christof Paar and JanPelzl Modified by Sam Bowne The PowerPoint PPT presentation: "Introduction to Stream Cipher" is the property of its rightful owner. * RC4 is a stream cipher designed in 1987 by Ron Rivest for RSA Security. Please see figure on the next slide synchronous stream cipher optimized for efficient hardware implementation at very high data rates. RC4 These slides are based on Lawrie Brown’s slides supplied with William Stallings ’s book “Cryptography and Network Security: Principles and Practice,” 5th Ed, 2011. If a truly random key stream is used, the result will be a truly 'random' ciphertext which bears no relation to the original plaintext. The rc4 stream cipher. 6. On other hand Stream Cipher is the type of encryption where the conversion of plain text performed by taking one byte of the plain text at a time. CS426 Fall 2010/Lecture 4 * Properties of CTR Gives a stream cipher from a block cipher subject to limitations of stream ciphers (what are they?) Randomized encryption: when starting counter is chosen randomly Random Access: decryption of a block can be done in random order, very useful for hard-disk encryption. STREAM CIPHERS. The primary advantage of a stream cipher is that stream ciphers are almost always faster and use far less code than do block ciphers. Examples of classical stream ciphers are the autokeyed Vigenère cipher and the Vernam cipher. A popular trend in stream cipher design is to turn to block-wise stream ciphers like RC4, SNOW 2. Administrators can choose to encrypt data by using a 56- or 128-bit key. Stream Cipher Structure A pseudorandom stream is one that is unpredictable without knowledge of the input key and which has an apparently random character. For a stream cipher implementation to remain secure, its pseudorandom generator should be unpredictable and the key should never be reused. Synchronous Stream Ciphers n-stage Linear Feedback Shift Register: consists of n bit register r = r0…rn–1 n bit tap sequence t = t0…tn–1 Use: Use rn–1 as key bit Compute x = r0t0 … rn–1tn–1 Shift r one bit to right, dropping rn–1, x becomes r0 Operation Example 4-stage LFSR; t = 1001 r ki new bit computation new r 0010 0 01 00 Substitution Algorithms are (Stream): Cesar Cipher Simple Key Substitution Monoalphabetic Cipher (Affine Cipher) Playfair Cipher Polyalphabetic Cipher (vigenere Cipher) Polyalphabetic Cipher (Vernam Cipher) One-Time Pad Transposition Algorithms are (Stream): Rail fence technique 2D matrix (One or more transpositions) Scytail Rotor Machines (Enigma) Security Requirement for wireless Network SECURITY GOALS-STREAM CIPHER Stream cipher functions on a stream of data by operating on it bit by bit. The same algorithm is used for both encryption and decryption as the data stream is simply XORed with the generated key sequence. While design principles and security of block ciphers are quite well un-derstood, stream cipher design still requires much research. E. Pair of efficient, deterministic algorithms (Init, GetBits) Inittakes a seed s (and optional IV), and outputs initial state st. In traditional stream cipher systems, the most common method of mixing plain text data bits with key bits is by performing the XOR operation on the corresponding bits. If a truly random key stream is used, the result will be a truly 'random' ciphertext which bears no relation to the original plaintext. During an n-bit key setup (n is t he key length), the encryption key is used to generat e an encrypting variabl e using two arrays, Stream Cipher Symmetric or secret-key encryption algorithm that encrypts a single bit at a time. I am a public-interest technologist, working at the intersection of security, technology, and people. Academia. The proposed algorithm uses a developed chaotic logistic map and an external secret key of 256Furthermore-bit. For any block cipher, and any key K, it is required that the function E K be a permutation on {0,1}n. 1 The Electronic Codebook Mode (ECB) 28 9. It makes a block cipher into a self- synchronizing stream cipher. 3 Two sh Building Blocks 3. My name is Abhishek Sharma. Keywords: Cryptanalysis, stream ciphers, Grain-128, cube attacks, cube testers, dynamic cube attacks. That is, the order of the units is changed. Assignment of class labels to PPTs and the generation of key stream is discussed in section 4. Operation is very similar to CBC; in particular, CFB decryption is almost identical to CBC encryption performed in reverse. Accordingly, the cube attack has been extensively used in the analysis of stream ciphers [6,10,11,24] because the attacker has to manipulate the input and analyze the output without evaluating the cipher PPT Version | PDF Version; Rahul Saxena Crosstalk between acidic phospholipids present in bacterial membranes and DnaA, the initiator of Escherichia coli chromosomal replication PPT Version | PDF Version; Jeffrey Zheng Pseudo DNA Sequence Generation of Non-coding Distributions using Stream Cipher Mechanism PPT Version | PDF Version; George W. A stream cipher is synchronous if its key sequence does not depend on the plain- and ciphertexts but only on the previous elements of the key sequence and the initial key. Parts of the plaintext is predictable (e. 1: The basic two enciphering principles. Secure stream cipher should satisfy the definition of a variable output-length pseudorandom generator. 11i formalization WPA Designed to be used with 802. Stream Ciphers 26 (No Transcript) 27 Stream Cipher Diagram 28 Stream Ciphers 29 Stream Ciphers 30 The RC4 Stream Cipher. stream cipher ppt