Search results “S box in cryptography definition”

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Introduction to Cryptology

Cryptography and Network Security by Prof. D. Mukhopadhyay, Department of Computer Science and Engineering, IIT Kharagpur. For more details on NPTEL visit http://nptel.iitm.ac.in

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nptelhrd

CSCI 361 Assignment 2 DES Video
Topic: Substitution Boxes (S-Box)
Video generated by Microsoft Powerpoint

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Jax Lee

What is SUBSTITUTION-PERMUTATION NETWORK? What does SUBSTITUTION-PERMUTATION NETWORK mean? SUBSTITUTION-PERMUTATION NETWORK meaning - SUBSTITUTION-PERMUTATION NETWORK definition - SUBSTITUTION-PERMUTATION NETWORK explanation.
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Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license.
In cryptography, an SP-network, or substitution–permutation network (SPN), is a series of linked mathematical operations used in block cipher algorithms such as AES (Rijndael), 3-Way, Kuznyechik, PRESENT, SAFER, SHARK, and Square.
Such a network takes a block of the plaintext and the key as inputs, and applies several alternating "rounds" or "layers" of substitution boxes (S-boxes) and permutation boxes (P-boxes) to produce the ciphertext block. The S-boxes and P-boxes transform (sub-)blocks of input bits into output bits. It is common for these transformations to be operations that are efficient to perform in hardware, such as exclusive or (XOR) and bitwise rotation. The key is introduced in each round, usually in the form of "round keys" derived from it. (In some designs, the S-boxes themselves depend on the key.)
Decryption is done by simply reversing the process (using the inverses of the S-boxes and P-boxes and applying the round keys in reversed order).
An S-box substitutes a small block of bits (the input of the S-box) by another block of bits (the output of the S-box). This substitution should be one-to-one, to ensure invertibility (hence decryption). In particular, the length of the output should be the same as the length of the input (the picture on the right has S-boxes with 4 input and 4 output bits), which is different from S-boxes in general that could also change the length, as in DES (Data Encryption Standard), for example. An S-box is usually not simply a permutation of the bits. Rather, a good S-box will have the property that changing one input bit will change about half of the output bits (or an avalanche effect). It will also have the property that each output bit will depend on every input bit.
A P-box is a permutation of all the bits: it takes the outputs of all the S-boxes of one round, permutes the bits, and feeds them into the S-boxes of the next round. A good P-box has the property that the output bits of any S-box are distributed to as many S-box inputs as possible.
At each round, the round key (obtained from the key with some simple operations, for instance, using S-boxes and P-boxes) is combined using some group operation, typically XOR.
A single typical S-box or a single P-box alone does not have much cryptographic strength: an S-box could be thought of as a substitution cipher, while a P-box could be thought of as a transposition cipher. However, a well-designed SP network with several alternating rounds of S- and P-boxes already satisfies Shannon's confusion and diffusion properties:
The reason for diffusion is the following: If one changes one bit of the plaintext, then it is fed into an S-box, whose output will change at several bits, then all these changes are distributed by the P-box among several S-boxes, hence the outputs of all of these S-boxes are again changed at several bits, and so on. Doing several rounds, each bit changes several times back and forth, therefore, by the end, the ciphertext has changed completely, in a pseudorandom manner. In particular, for a randomly chosen input block, if one flips the i-th bit, then the probability that the j-th output bit will change is approximately a half, for any i and j, which is the Strict Avalanche Criterion. Vice versa, if one changes one bit of the ciphertext, then attempts to decrypt it, the result is a message completely different from the original plaintext—SP ciphers are not easily malleable.....

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The Audiopedia

AES Steps: Substitute Bytes, Shift Rows, Mix Columns, GF Arithmetic

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Natarajan Meghanathan

Easy explanation of "public key encryption".
Instead of the usual terms of "public key" and "private key" this tutorial uses "lock" and "key".
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Veet Vivarto

This lecture explains Block Cipher primitives.

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Project Rhea

What is DISTINGUISHING ATTACK? What does DISTINGUISHING ATTACK mean? DISTINGUISHING ATTACK meaning - DISTINGUISHING ATTACK definition - DISTINGUISHING ATTACK explanation.
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In cryptography, a distinguishing attack is any form of cryptanalysis on data encrypted by a cipher that allows an attacker to distinguish the encrypted data from random data. Modern symmetric-key ciphers are specifically designed to be immune to such an attack. In other words, modern encryption schemes are pseudorandom permutations and are designed to have ciphertext indistinguishability. If an algorithm is found that can distinguish the output from random faster than a brute force search, then that is considered a break of the cipher.
A similar concept is the known-key distinguishing attack, whereby an attacker knows the key and can find a structural property in cipher, where the transformation from plaintext to ciphertext is not random.
To prove that a cryptographic function is safe, it is often compared to a random oracle. If a function would be a random oracle, then an attacker is not able to predict any of the output of the function. If a function is distinguishable from a random oracle, it has non-random properties. That is, there exists a relation between different outputs, or between input and output, which can be used by an attacker for example to find (a part of) the input.
Example Let T be a sequence of random bits, generated by a random oracle and S be a sequence generated by a pseudo-random bit generator. Two parties use one encryption system to encrypt a message M of length n as the bitwise XOR of M and the next n bits of T or S respectively. The output of the encryption using T is truly random. Now if the sequence S cannot be distinguished from T, the output of the encryption with S will appear random as well. If the sequence S is distinguishable, then the encryption of M with S may reveal information of M.
Two systems S and T are said to be indistinguishable if there exists no algorithm D, connected to either S or T, able to decide whether it is connected to S or T.
A distinguishing attack is given by such an algorithm D. It is broadly an attack in which the attacker is given a black box containing either an instance of the system under attack with an unknown key, or a random object in the domain that the system aims to emulate, then if the algorithm is able to tell whether the system or the random object is in the black box, one has an attack. For example, a distinguishing attack on a stream cipher such as RC4 might be one that determines whether a given stream of bytes is random or generated by RC4 with an unknown key.
Classic examples of distinguishing attack on a popular stream cipher was by Itsik Mantin and Adi Shamir who showed that the 2nd output byte of RC4 was heavily biased toward zero. In another example, Souradyuti Paul and Bart Preneel of COSIC have shown that the XOR value of the 1st and 2nd outputs of RC4 is also non-uniform. Significantly, both the above theoretical biases can be demonstrable through computer simulation.

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The Audiopedia

Talk at crypto 2012. Authors: Eric Miles, Emanuele Viola. See http://www.iacr.org/cryptodb/data/paper.php?pubkey=24289

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TheIACR

December 2, 2009
Dan Brown? The Lost Symbol?
Masonic cipher? Albrecht Durers magic square?
If you know about these things AND you can decipher the message below,
then dont bother coming because you know as much as I do.
If you dont know about them OR you cant decipher the message below,
then by all means come and hear my presentation.
Yes, we do have pizza.
Ed Brumgnach
http://www.qcc.cuny.edu/ecet/magicSquares.asp

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CUNYQueensborough

Cryptography and Network Security by Prof. D. Mukhopadhyay, Department of Computer Science and Engineering, IIT Kharagpur. For more details on NPTEL visit http://nptel.iitm.ac.in

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nptelhrd

What is PRODUCT CIPHER? What does PRODUCT CIPHER mean? PRODUCT CIPHER meaning - PRODUCT CIPHER definition - PRODUCT CIPHER explanation.
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Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license.
In cryptography, a product cipher combines two or more transformations in a manner intending that the resulting cipher is more secure than the individual components to make it resistant to cryptanalysis. The product cipher combines a sequence of simple transformations such as substitution (S-box), permutation (P-box), and modular arithmetic. The concept of product ciphers is due to Claude Shannon, who presented the idea in his foundational paper, Communication Theory of Secrecy Systems.
For transformation involving reasonable number of n message symbols, both of the foregoing cipher systems (the S-box and P-box) are by themselves wanting. Shannon suggested using a combination of S-box and P-box transformation—a product cipher. The combination could yield a cipher system more powerful than either one alone. This approach of alternatively applying substitution and permutation transformation has been used by IBM in the Lucifer cipher system, and has become the standard for national data encryption standards such as the Data Encryption Standard and the Advanced Encryption Standard. A product cipher that uses only substitutions and permutations is called a SP-network. Feistel ciphers are an important class of product ciphers.

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The Audiopedia

Cryptography and Network Security by Prof. D. Mukhopadhyay, Department of Computer Science and Engineering, IIT Kharagpur. For more details on NPTEL visit http://nptel.iitm.ac.in

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nptelhrd

Claude Shannon's idea of perfect secrecy: no amount of computational power can help improve your ability to break the one-time pad
Watch the next lesson: https://www.khanacademy.org/computing/computer-science/cryptography/crypt/v/random-vs-pseudorandom-number-generators?utm_source=YT&utm_medium=Desc&utm_campaign=computerscience
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Computer Science on Khan Academy: Learn select topics from computer science - algorithms (how we solve common problems in computer science and measure the efficiency of our solutions), cryptography (how we protect secret information), and information theory (how we encode and compress information).
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Khan Academy Labs

Modern day encryption is performed in two different ways. Check out http://YouTube.com/ITFreeTraining or http://itfreetraining.com for more of our always free training videos. Using the same key or using a pair of keys called the public and private keys. This video looks at how these systems work and how they can be used together to perform encryption.
Download the PDF handout
http://itfreetraining.com/Handouts/Ce...
Encryption Types
Encryption is the process of scrambling data so it cannot be read without a decryption key. Encryption prevents data being read by a 3rd party if it is intercepted by a 3rd party. The two encryption methods that are used today are symmetric and public key encryption.
Symmetric Key
Symmetric key encryption uses the same key to encrypt data as decrypt data. This is generally quite fast when compared with public key encryption. In order to protect the data, the key needs to be secured. If a 3rd party was able to gain access to the key, they could decrypt any data that was encrypt with that data. For this reason, a secure channel is required to transfer the key if you need to transfer data between two points. For example, if you encrypted data on a CD and mail it to another party, the key must also be transferred to the second party so that they can decrypt the data. This is often done using e-mail or the telephone. In a lot of cases, sending the data using one method and the key using another method is enough to protect the data as an attacker would need to get both in order to decrypt the data.
Public Key Encryption
This method of encryption uses two keys. One key is used to encrypt data and the other key is used to decrypt data. The advantage of this is that the public key can be downloaded by anyone. Anyone with the public key can encrypt data that can only be decrypted using a private key. This means the public key does not need to be secured. The private key does need to be keep in a safe place. The advantage of using such a system is the private key is not required by the other party to perform encryption. Since the private key does not need to be transferred to the second party there is no risk of the private key being intercepted by a 3rd party. Public Key encryption is slower when compared with symmetric key so it is not always suitable for every application. The math used is complex but to put it simply it uses the modulus or remainder operator. For example, if you wanted to solve X mod 5 = 2, the possible solutions would be 2, 7, 12 and so on. The private key provides additional information which allows the problem to be solved easily. The math is more complex and uses much larger numbers than this but basically public and private key encryption rely on the modulus operator to work.
Combing The Two
There are two reasons you want to combine the two. The first is that often communication will be broken into two steps. Key exchange and data exchange. For key exchange, to protect the key used in data exchange it is often encrypted using public key encryption. Although slower than symmetric key encryption, this method ensures the key cannot accessed by a 3rd party while being transferred. Since the key has been transferred using a secure channel, a symmetric key can be used for data exchange. In some cases, data exchange may be done using public key encryption. If this is the case, often the data exchange will be done using a small key size to reduce the processing time.
The second reason that both may be used is when a symmetric key is used and the key needs to be provided to multiple users. For example, if you are using encryption file system (EFS) this allows multiple users to access the same file, which includes recovery users. In order to make this possible, multiple copies of the same key are stored in the file and protected from being read by encrypting it with the public key of each user that requires access.
References
"Public-key cryptography" http://en.wikipedia.org/wiki/Public-k...
"Encryption" http://en.wikipedia.org/wiki/Encryption

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itfreetraining

https://8gwifi.org/CipherFunctions.jsp
Reference book: http://leanpub.com/crypto
Computer Security, Cryptography Advanced Encryption Standard AES,fips 197
The Advanced Encryption Standard (AES) specifies a FIPS-approved
cryptographic algorithm that can be used to protect electronic data. The AES algorithm is a symmetric block cipher that can encrypt (encipher) and decrypt (decipher) information. Encryption converts data to an unintelligible form called ciphertext; decrypting the ciphertext converts the data back into its original form, called plaintext.
The AES algorithm is capable of using cryptographic keys of 128, 192, and 256 bits to encrypt and decrypt data in blocks of 128 bits.
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Zariga Tongy

A video of flash animation of the cipher used for AES encryption process.
Disclaimer: I did the work of creating video from flash animation. Credit of flash animation goes to its author. At the moment, I do not have a link to the source for flash animation.

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AAA

What is S-1 BLOCK CIPHER? What does S-1 BLOCK CIPHER mean? S-1 BLOCK CIPHER meaning - S-1 BLOCK CIPHER definition - S-1 BLOCK CIPHER explanation.
Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license.
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In cryptography, the S-1 block cipher was a block cipher posted in source code form on Usenet on 11 August 1995. Although incorrect security markings immediately indicated a hoax, there were several features of the code which suggested it might be leaked source code for the Skipjack cipher, which was still classified at the time.
However once David Wagner had discovered a severe design flaw, involving the key schedule but not the underlying round function, it was generally accepted as being a hoax—but one with an astonishing amount of work behind it. Bruce Schneier noted that S-1 contained a feature never seen before in the open literature; a G-table that results in key and data dependent rotation of S-boxes to use in a given round . When Skipjack was eventually declassified in 1998, it was indeed found to be totally unlike S-1.

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The Audiopedia

What is INTERPOLATION ATTACK? What does INTERPOLATION ATTACK mean? INTERPOLATION ATTACK meaning - INTERPOLATION ATTACK definition - INTERPOLATION ATTACK explanation.
Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license.
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In cryptography, an interpolation attack is a type of cryptanalytic attack against block ciphers.
After the two attacks, differential cryptanalysis and linear cryptanalysis, were presented on block ciphers, some new block ciphers were introduced, which were proven secure against differential and linear attacks. Among these there were some iterated block ciphers such as the KN-Cipher and the SHARK cipher. However, Thomas Jakobsen and Lars Knudsen showed in the late 90's that these ciphers were easy to break by introducing a new attack called the interpolation attack.
In the attack, an algebraic function is used to represent an S-box. This may be a simple quadratic, or a polynomial or rational function over a Galois field. Its coefficients can be determined by standard Lagrange interpolation techniques, using known plaintexts as data points. Alternatively, chosen plaintexts can be used to simplify the equations and optimize the attack.
In its simplest version an interpolation attack expresses the ciphertext as a polynomial of the plaintext. If the polynomial has a relative low number of unknown coefficients, then with a collection of plaintext/ciphertext (p/c) pairs, the polynomial can be reconstructed. With the polynomial reconstructed the attacker then has a representation of the encryption, without exact knowledge of the secret key.
The interpolation attack can also be used to recover the secret key.
It is easiest to describe the method with an example.

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The Audiopedia

What is AVALANCHE EFFECT? What does AVALANCHE EFFECT mean? AVALANCHE EFFECT meaning - AVALANCHE EFFECT definition - AVALANCHE EFFECT explanation.
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Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license.
In cryptography, the avalanche effect is the desirable property of cryptographic algorithms, typically block ciphers and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext. The actual term was first used by Horst Feistel, although the concept dates back to at least Shannon's diffusion.
If a block cipher or cryptographic hash function does not exhibit the avalanche effect to a significant degree, then it has poor randomization, and thus a cryptanalyst can make predictions about the input, being given only the output. This may be sufficient to partially or completely break the algorithm. Thus, the avalanche effect is a desirable condition from the point of view of the designer of the cryptographic algorithm or device.
Constructing a cipher or hash to exhibit a substantial avalanche effect is one of the primary design objectives, and mathematically the construction takes advantage of butterfly effect. This is why most block ciphers are product ciphers. It is also why hash functions have large data blocks. Both of these features allow small changes to propagate rapidly through iterations of the algorithm, such that every bit of the output should depend on every bit of the input before the algorithm terminates.
The strict avalanche criterion (SAC) is a formalization of the avalanche effect. It is satisfied if, whenever a single input bit is complemented, each of the output bits changes with a 50% probability. The SAC builds on the concepts of completeness and avalanche and was introduced by Webster and Tavares in 1985.
Higher-order generalizations of SAC involve multiple input bits. Boolean functions which satisfy the highest order SAC are always bent functions, also called maximally nonlinear functions, also called "perfect nonlinear" functions.

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The Audiopedia

https://8gwifi.org/CipherFunctions.jsp
Encryption Decryption Online https://8gwifi.org/CipherFunctions.jsp
what is DES DATA ENCRYPTION STANDARD (DES)
The Data Encryption Standard (DES) specifies two FIPS approved
cryptographic algorithms as required by FIPS 140-1. When used in conjunction with American
National Standards Institute (ANSI) X9.52 standard, this publication provides a complete description
of the mathematical algorithms for encrypting (enciphering) and decrypting (deciphering) binary
coded information. Encrypting data converts it to an unintelligible form called cipher. Decrypting
cipher converts the data back to its original form called plaintext. The algorithms described in this
standard specifies both enciphering and deciphering operations which are based on a binary number
called a key
computer security cryptography
data encryption standard animation

Views: 68853
Zariga Tongy

What is IMPOSSIBLE DIFFERENTIAL CRYPTANALYSIS? What does IMPOSSIBLE DIFFERENTIAL CRYPTANALYSIS mean? IMPOSSIBLE DIFFERENTIAL CRYPTANALYSIS meaning - IMPOSSIBLE DIFFERENTIAL CRYPTANALYSIS definition - IMPOSSIBLE DIFFERENTIAL CRYPTANALYSIS explanation.
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In cryptography, impossible differential cryptanalysis is a form of differential cryptanalysis for block ciphers. While ordinary differential cryptanalysis tracks differences that propagate through the cipher with greater than expected probability, impossible differential cryptanalysis exploits differences that are impossible (having probability 0) at some intermediate state of the cipher algorithm.
Lars Knudsen appears to be the first to use a form of this attack, in the 1998 paper where he introduced his AES candidate, DEAL. The first presentation to attract the attention of the cryptographic community was later the same year at the rump session of CRYPTO '98, in which Eli Biham, Alex Biryukov, and Adi Shamir introduced the name "impossible differential" and used the technique to break 4.5 out of 8.5 rounds of IDEA and 31 out of 32 rounds of the NSA-designed cipher Skipjack. This development led cryptographer Bruce Schneier to speculate that the NSA had no previous knowledge of impossible differential cryptanalysis. The technique has since been applied to many other ciphers: Khufu and Khafre, E2, variants of Serpent, MARS, Twofish, Rijndael, CRYPTON, Zodiac, Hierocrypt-3, TEA, XTEA, Mini-AES, ARIA, Camellia, and SHACAL-2.
Biham, Biryukov and Shamir also presented a relatively efficient specialized method for finding impossible differentials that they called a miss-in-the-middle attack. This consists of finding "two events with probability one, whose conditions cannot be met together."

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The Audiopedia

Video is created with the help of wikipedia, if you are looking for accurate, professional translation services and efficient localization you can use Universal Translation Services https://www.universal-translation-services.com?ap_id=ViragGNG Video shows what 3DES means. Triple DES, a cipher formed from the Data Encryption Standard (DES) cipher by using it three times.. 3DES Meaning. How to pronounce, definition audio dictionary. How to say 3DES. Powered by MaryTTS, Wiktionary

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ADictionary

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Internetwork Security

#askfaizan | #syedfaizanahmad
Block Cipher Modes of Operation | CBC mode | Part 2 https://youtu.be/Q7LKmASkVSU
Hill Cipher | Complete Algorithm with Example https://youtu.be/B0Q7w7Fd7ms
Playfair Substitution Cipher https://youtu.be/w_xr7pj-O6c
Monoalphabetic Substitution Cipher https://youtu.be/Hw1T7GOnVW0
Caesar Cipher | Caesar Substitution Cipher https://youtu.be/2N9GlhysYJw
PlayList : Cryptography and Network Security : https://www.youtube.com/playlist?list=PLhwpdymnbXz7hvvqhqjIIG4tEdhAgQqll
Block cipher processes the data blocks of fixed size
If size of message is larger than block size. Then, the message is divided into a series of sequential message blocks.
Multiple blocks of plaintext are encrypted using the same key, security issues arise.
To apply a block cipher in a variety of applications, five modes of operation have been defined by NIST
1. Electronic Code Book Mode
2. Cipher Block Chaining Mode
3. Output Feedback Mode
4. Cipher Feedback Mode
5. Counter Mode
The simplest mode is the electronic codebook (ECB) mode
Plaintext is handled one block at a time
Each block of plaintext is encrypted using the same key
The ECB mode is deterministic
If plaintext block P1, P2,…, Pm are encrypted twice under the same key, the output ciphertext blocks will be the same.
CBC is technique in which the same plaintext block, if repeated, produces different ciphertext blocks
Each plaintext block is XORed with the ciphertext block that was previously produced
To produce the first block of ciphertext, an initialization vector (IV) is XORed with the first block of plaintext
For decryption, IV data is XORed with first ciphertext block decrypted.

Views: 206
Ask Faizan

MIT 6.046J Design and Analysis of Algorithms, Spring 2015
View the complete course: http://ocw.mit.edu/6-046JS15
Instructor: Srinivas Devadas
In this lecture, Professor Devadas continues with cryptography, introducing encryption methods.
License: Creative Commons BY-NC-SA
More information at http://ocw.mit.edu/terms
More courses at http://ocw.mit.edu

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MIT OpenCourseWare

Google Tech Talks
November, 28 2007
Topics include: Introduction to Modern Cryptography, Using Cryptography in Practice and at Google, Proofs of Security and Security Definitions and A Special Topic in Cryptography
This talk is one in a series hosted by Google University: Wednesdays, 11/28/07 - 12/19/07 from 1-2pm
Speaker: Steve Weis
Steve Weis received his PhD from the Cryptography and Information Security group at MIT, where he was advised by Ron Rivest. He is a member of Google's Applied Security (AppSec) team and is the technical lead for Google's internal cryptographic library, KeyMaster.

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GoogleTechTalks

What is CUBE ATTACK? What does CUBE ATTACK mean? CUBE ATTACK meaning - CUBE ATTACK definition - CUBE ATTACK explanation.
Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license.
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The cube attack is a method of cryptanalysis applicable to a wide variety of symmetric-key algorithms, published by Itai Dinur and Adi Shamir in a September 2008 preprint. A revised version of this preprint was placed online in January 2009, and the paper has also been accepted for presentation at Eurocrypt 2009.
A cipher is vulnerable if an output bit can be represented as a sufficiently low degree polynomial over GF(2) of key and input bits; in particular, this describes many stream ciphers based on LFSRs. DES and AES are believed to be immune to this attack. It works by summing an output bit value for all possible values of a subset of public input bits, chosen such that the resulting sum is a linear combination of secret bits; repeated application of this technique gives a set of linear relations between secret bits that can be solved to discover these bits. The authors show that if the cipher resembles a random polynomial of sufficiently low degree then such sets of public input bits will exist with high probability, and can be discovered in a precomputation phase by "black box probing" of the relationship between input and output for various choices of public and secret input bits making no use of any other information about the construction of the cipher.
The paper presents a practical attack, which the authors have implemented and tested, on a stream cipher on which no previous known attack would be effective. Its state is a 10,000 bit LFSR with a secret dense feedback polynomial, which is filtered by an array of 1000 secret 8-bit to 1-bit S-boxes, whose input is based on secret taps into the LFSR state and whose output is XORed together. Each bit in the LFSR is initialized by a different secret dense quadratic polynomial in 10, 000 key and IV bits. The LFSR is clocked a large and secret number of times without producing any outputs, and then only the first output bit for any given IV is made available to the attacker. After a short preprocessing phase in which the attacker can query output bits for a variety of key and IV combinations, only 230 bit operations are required to discover the key for this cipher.
The authors also claim an attack on a version of Trivium reduced to 735 initialization rounds with complexity 230, and conjecture that these techniques may extend to breaking 1100 of Trivium's 1152 initialization rounds and "maybe even the original cipher". As of December 2008 this is the best attack known against Trivium.
The attack is, however, embroiled in two separate controversies. Firstly, Daniel J. Bernstein disputes the assertion that no previous attack on the 10,000-bit LFSR-based stream cipher existed, and claims that the attack on reduced-round Trivium "doesn't give any real reason to think that (the full) Trivium can be attacked". He claims that the Cube paper failed to cite an existing paper by Xuejia Lai detailing an attack on ciphers with small-degree polynomials, and that he believes the Cube attack to be merely a reinvention of this existing technique.
Secondly, Dinur and Shamir credit Michael Vielhaber's "Algebraic IV Differential Attack" (AIDA) as a precursor of the Cube attack. Dinur has stated at Eurocrypt 2009 that Cube generalises and improves upon AIDA. However, Vielhaber contends that the cube attack is no more than his attack under another name. It is, however, acknowledged by all parties involved that Cube's use of an efficient linearity test such as the BLR test results in the new attack needing less time than AIDA, although how substantial this particular change is remains in dispute. It is not the only way in which Cube and AIDA differ. Vielhaber claims, for instance, that the linear polynomials in the key bits that are obtained during the attack will be unusually sparse. He has not yet supplied evidence of this, but claims that such evidence will appear in a forthcoming paper by himself entitled "The Algebraic IV Differential Attack: AIDA Attacking the full Trivium". (It is not clear whether this alleged sparsity applies to any ciphers other than Trivium.)

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The Audiopedia

This video is part of an online course, Applied Cryptography. Check out the course here: https://www.udacity.com/course/cs387.

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Udacity

This video is part of an online course, Applied Cryptography. Check out the course here: https://www.udacity.com/course/cs387.

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Udacity

Namaskaar Dosto, maine is video mein aapse Digital Signatures ke baare mein baat ki hai, aap sabhi ne bahut baar inke baare mein suna hoga, daily life mein toh aap sabhi signatures ko use karte hai, but Digital Signatures ekdum alag concept hai aur kaafi important bhi hai. Mujhe umeed hai ki aapko Digital Signatures ke baare mein yeh video pasand aayega.
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Technical Guruji

Demonstration of a timing-based side channel attack. This attack takes advantage of a known timing imbalance in the standard ANSI C memcmp function, in which it exits as soon as a compared byte does not match. This results in the function taking a longer time given the more bytes that match between the compared blocks of memory. As long as there's a measurable timing imbalance, a system can be exploited regardless of the particular compare process used.
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Joe Grand

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nptelhrd

What is RANDOM ORACLE? What does RANDOM ORACLE mean? RANDOM ORACLE meaning - RANDOM ORACLE definition - RANDOM ORACLE explanation.
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In cryptography, a random oracle is an oracle (a theoretical black box) that responds to every unique query with a (truly) random response chosen uniformly from its output domain. If a query is repeated it responds the same way every time that query is submitted.
Stated differently, a random oracle is a mathematical function chosen uniformly at random, that is, a function mapping each possible query to a (fixed) random response from its output domain.
Random oracles as a mathematical abstraction were firstly used in rigorous cryptographic proofs in the 1993 publication by Mihir Bellare and Phillip Rogaway (1993). They are typically used when the cryptographic hash functions in the method cannot be proven to possess the mathematical properties required by the proof. A system that is proven secure when every hash function is replaced by a random oracle is described as being secure in the random oracle model, as opposed to secure in the standard model of cryptography.
Random oracles are typically used as an ideal replacement for cryptographic hash functions in schemes where strong randomness assumptions are needed of the hash function's output. Such a proof generally shows that a system or a protocol is secure by showing that an attacker must require impossible behavior from the oracle, or solve some mathematical problem believed hard in order to break it.
Not all uses of cryptographic hash functions require random oracles: schemes that require only one or more properties having a definition in the standard model (such as collision resistance, preimage resistance, second preimage resistance, etc.) can often be proven secure in the standard model (e.g., the Cramer–Shoup cryptosystem).
Random oracles have long been considered in computational complexity theory, and many schemes have been proven secure in the random oracle model, for example Optimal Asymmetric Encryption Padding, RSA-FDH and Probabilistic Signature Scheme. In 1986, Amos Fiat and Adi Shamir showed a major application of random oracles – the removal of interaction from protocols for the creation of signatures.
In 1989, Russell Impagliazzo and Steven Rudich showed the limitation of random oracles – namely that their existence alone is not sufficient for secret-key exchange.
In 1993, Mihir Bellare and Phillip Rogaway were the first to advocate their use in cryptographic constructions. In their definition, the random oracle produces a bit-string of infinite length which can be truncated to the length desired.
According to the Church–Turing thesis, no function computable by a finite algorithm can implement a true random oracle (which by definition requires an infinite description).
In fact, certain artificial signature and encryption schemes are known which are proven secure in the random oracle model, but which are trivially insecure when any real function is substituted for the random oracle. Nonetheless, for any more natural protocol a proof of security in the random oracle model gives very strong evidence of the practical security of the protocol.
In general, if a protocol is proven secure, attacks to that protocol must either be outside what was proven, or break one of the assumptions in the proof; for instance if the proof relies on the hardness of integer factorization, to break this assumption one must discover a fast integer factorization algorithm. Instead, to break the random oracle assumption, one must discover some unknown and undesirable property of the actual hash function; for good hash functions where such properties are believed unlikely, the considered protocol can be considered secure.

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The Audiopedia

In cryptography, Triple DES (3DES) is the common name for the Triple Data Encryption Algorithm (TDEA or Triple DEA) symmetric-key block cipher, which applies the Data Encryption Standard (DES) cipher algorithm three times to each data block.
The original DES cipher's key size of 56 bits was generally sufficient when that algorithm was designed, but the availability of increasing computational power made brute-force attacks feasible. Triple DES provides a relatively simple method of increasing the key size of DES to protect against such attacks, without the need to design a completely new block cipher algorithm.
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Audiopedia

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nptelhrd

For more information: https://www.bitcoinmining.com and https://www.weusecoins.com
What is Bitcoin Mining? Have you ever wondered how Bitcoin is generated? This short video is an animated introduction to Bitcoin Mining.
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BitcoinMiningCom

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nptelhrd

What is XSL ATTACK? What does XSL ATTACK mean? XSL ATTACK meaning - XSL ATTACK definition - XSL ATTACK explanation.
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In cryptography, the eXtended Sparse Linearization (XSL) attack is a method of cryptanalysis for block ciphers. The attack was first published in 2002 by researchers Nicolas Courtois and Josef Pieprzyk. It has caused some controversy as it was claimed to have the potential to break the Advanced Encryption Standard (AES) cipher, also known as Rijndael, faster than an exhaustive search. Since AES is already widely used in commerce and government for the transmission of secret information, finding a technique that can shorten the amount of time it takes to retrieve the secret message without having the key could have wide implications.
The method has a high work-factor, which unless lessened, means the technique does not reduce the effort to break AES in comparison to an exhaustive search. Therefore, it does not affect the real-world security of block ciphers in the near future. Nonetheless, the attack has caused some experts to express greater unease at the algebraic simplicity of the current AES.
In overview, the XSL attack relies on first analyzing the internals of a cipher and deriving a system of quadratic simultaneous equations. These systems of equations are typically very large, for example 8,000 equations with 1,600 variables for the 128-bit AES. Several methods for solving such systems are known. In the XSL attack, a specialized algorithm, termed eXtended Sparse Linearization, is then applied to solve these equations and recover the key.
The attack is notable for requiring only a handful of known plaintexts to perform; previous methods of cryptanalysis, such as linear and differential cryptanalysis, often require unrealistically large numbers of known or chosen plaintexts.
Solving multivariate quadratic equations (MQ) over a finite set of numbers is an NP-hard problem (in the general case) with several applications in cryptography. The XSL attack requires an efficient algorithm for tackling MQ. In 1999, Kipnis and Shamir showed that a particular public key algorithm, known as the Hidden Field Equations scheme (HFE), could be reduced to an overdetermined system of quadratic equations (more equations than unknowns). One technique for solving such systems is linearization, which involves replacing each quadratic term with an independent variable and solving the resultant linear system using an algorithm such as Gaussian elimination. To succeed, linearization requires enough linearly independent equations (approximately as many as the number of terms). However, for the cryptanalysis of HFE there were too few equations, so Kipnis and Shamir proposed re-linearization, a technique where extra non-linear equations are added after linearization, and the resultant system is solved by a second application of linearization. Re-linearization proved general enough to be applicable to other schemes.
In 2000, Courtois et al. proposed an improved algorithm for MQ known as XL (for eXtended Linearization), which increases the number of equations by multiplying them with all monomials of a certain degree. Complexity estimates showed that the XL attack would not work against the equations derived from block ciphers such as AES. However, the systems of equations produced had a special structure, and the XSL algorithm was developed as a refinement of XL which could take advantage of this structure. In XSL, the equations are multiplied only by carefully selected monomials, and several variants have been proposed.
Research into the efficiency of XL and its derivative algorithms remains ongoing (Yang and Chen, 2004).
Courtois and Pieprzyk (2002) observed that AES (Rijndael) and partially also Serpent could be expressed as a system of quadratic equations. The variables represent not just the plaintext, ciphertext and key bits, but also various intermediate values within the algorithm. The S-box of AES appears to be especially vulnerable to this type of analysis, as it is based on the algebraically simple inverse function. ...

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The Audiopedia

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Learning Symmetric Cryptography: Transposition Cipher
In this video Tripti Tanvi has explained the Transposition Cipher. Also, learn rail fence, simple columnar and complex transposition techniques.
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The Sieve of Eratosthenes is a simple, ancient algorithm for finding all prime numbers up to a specified integer. In this case we are using a 100's chart.

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Cryptography Stream ciphers and pseudo random generators
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About this course: Cryptography is an indispensable tool for protecting information in computer systems. In this course you will learn the inner workings of cryptographic systems and how to correctly use them in real-world applications. The course begins with a detailed discussion of how two parties who have a shared secret key can communicate securely when a powerful adversary eavesdrops and tampers with traffic. We will examine many deployed protocols and analyze mistakes in existing systems. The second half of the course discusses public-key techniques that let two parties generate a shared secret key.

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intrigano

Confusion and diffusion
In cryptography, confusion and diffusion are two properties of the operation of a secure cipher identified by Claude Shannon in his 1945 classified report A Mathematical Theory of Cryptography.Confusion means that each binary digit (bit) of the ciphertext should depend on several parts of the key.
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