CRYPTOGRAPHY and NETWORK SECURITY LECTURE NOTES for Bachelor of Technology in Computer Science and Engineering & Information Technology
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Improved Cryptanalysis of the Reduced Grøstl Compression Function, ECHO Permutation and AES Block Cipher
Improved Cryptanalysis of the Reduced Grøstl Compression Function, ECHO Permutation and AES Block Cipher Florian Mendel1, Thomas Peyrin2, Christian Rechberger1, and Martin Schl¨affer1 1 IAIK, Graz University of Technology, Austria 2 Ingenico, France [email protected],[email protected] Abstract. In this paper, we propose two new ways to mount attacks on the SHA-3 candidates Grøstl, and ECHO, and apply these attacks also to the AES. Our results improve upon and extend the rebound attack. Using the new techniques, we are able to extend the number of rounds in which available degrees of freedom can be used. As a result, we present the first attack on 7 rounds for the Grøstl-256 output transformation3 and improve the semi-free-start collision attack on 6 rounds. Further, we present an improved known-key distinguisher for 7 rounds of the AES block cipher and the internal permutation used in ECHO. Keywords: hash function, block cipher, cryptanalysis, semi-free-start collision, known-key distinguisher 1 Introduction Recently, a new wave of hash function proposals appeared, following a call for submissions to the SHA-3 contest organized by NIST [26]. In order to analyze these proposals, the toolbox which is at the cryptanalysts' disposal needs to be extended. Meet-in-the-middle and differential attacks are commonly used. A recent extension of differential cryptanalysis to hash functions is the rebound attack [22] originally applied to reduced (7.5 rounds) Whirlpool (standardized since 2000 by ISO/IEC 10118-3:2004) and a reduced version (6 rounds) of the SHA-3 candidate Grøstl-256 [14], which both have 10 rounds in total. -
The 5 Things You Need to Do to Protect Yourself from Ransomware
THE 5 THINGS YOU NEED TO DO TO PROTECT YOURSELF FROM RANSOMWARE ARE YOU RANSOMWARE-AWARE? In our recent survey* of more than RANSOMWARE is malware sent The 5 things you need to do to protect 3,000 people in the U.S. and Canada by criminals that encrypts your we learned that many are unaware of files and threatens to delete yourself from ransomware ransomware or how to defend against it. them if you don’t pay a ransom. By Stephen Cobb, ESET Senior Security Researcher ...said85% they would not pay the ransom fee and just risk losing their files, and Family photos and videos. Tax returns and other financial records. Business 15% said they would pay and take the chance that they may not even get documents. Think about everything that you keep on your computer. What their files back. would happen if it all was stolen from you? ...of42% people did not know if the internet That’s what a ransomware attack does. Criminals use this nasty breed security/antivirus they were using helped protect them from ransomware. of software to reach out over your internet connection and kidnap the contents of your computer, literally holding them for ransom. Ransomware silently encrypts all of your personal files, making them unreadable, and then demands that you send money to the criminal in order to restore them. ...of31% respondents NEVER backup their files. Those in the youngest age bracket (18-24) were the most likely age group to never back up files (35%). We surveyed over 3,000 people across the U.S. -
Key-Dependent Approximations in Cryptanalysis. an Application of Multiple Z4 and Non-Linear Approximations
KEY-DEPENDENT APPROXIMATIONS IN CRYPTANALYSIS. AN APPLICATION OF MULTIPLE Z4 AND NON-LINEAR APPROXIMATIONS. FX Standaert, G Rouvroy, G Piret, JJ Quisquater, JD Legat Universite Catholique de Louvain, UCL Crypto Group, Place du Levant, 3, 1348 Louvain-la-Neuve, standaert,rouvroy,piret,quisquater,[email protected] Linear cryptanalysis is a powerful cryptanalytic technique that makes use of a linear approximation over some rounds of a cipher, combined with one (or two) round(s) of key guess. This key guess is usually performed by a partial decryp- tion over every possible key. In this paper, we investigate a particular class of non-linear boolean functions that allows to mount key-dependent approximations of s-boxes. Replacing the classical key guess by these key-dependent approxima- tions allows to quickly distinguish a set of keys including the correct one. By combining different relations, we can make up a system of equations whose solu- tion is the correct key. The resulting attack allows larger flexibility and improves the success rate in some contexts. We apply it to the block cipher Q. In parallel, we propose a chosen-plaintext attack against Q that reduces the required number of plaintext-ciphertext pairs from 297 to 287. 1. INTRODUCTION In its basic version, linear cryptanalysis is a known-plaintext attack that uses a linear relation between input-bits, output-bits and key-bits of an encryption algorithm that holds with a certain probability. If enough plaintext-ciphertext pairs are provided, this approximation can be used to assign probabilities to the possible keys and to locate the most probable one. -
Internet Security
Internet Security Thompson Davis & Co. (TD & Co.) is committed to protecting the security and confidentiality of customer information. We use a combination of state-of-the-art technology and methods to help to protect the security of your online information. • Internet Communication Security Measures - Any sensitive personal information that you send through TD & Co. is held in a secured environment, protected by tools such as firewalls and/or database field encryption. Please do not send any sensitive or personal information over email. TD & Co. will not electronically send any personal financial information to you unless you request us to do so. • Protect Yourself from Fraudulent Web Sites - Personal information shared over the Internet can be used to commit fraud. One common method is for thieves to create a web site using a name that is similar to that of a reputable business, for instance by using a common misspelling of the company's name. The intent is to lure you into clicking onto the copycat web site and giving your personal information, including your account number and password. We caution you to make sure of whom you are dealing with over the Internet and to understand what will be done with your information. Always check that you have typed the correct web site address before entering personal information onto a site. • Personal Computer Security – Regardless of the security measures TD & Co. takes to protect your online financial information, if the computer or network you are using to access this data is not secure, you run the risk of your financial information being compromised. -
Intro to Cryptography 1 Introduction 2 Secure Password Manager
Programming Assignment 1 Winter 2021 CS 255: Intro to Cryptography Prof. Dan Boneh Due Monday, Feb. 8, 11:59pm 1 Introduction In many software systems today, the primary weakness often lies in the user’s password. This is especially apparent in light of recent security breaches that have highlighted some of the weak passwords people commonly use (e.g., 123456 or password). It is very important, then, that users choose strong passwords (or “passphrases”) to secure their accounts, but strong passwords can be long and unwieldy. Even more problematic, the user generally has many different services that use password authentication, and as a result, the user has to recall many different passwords. One way for users to address this problem is to use a password manager, such as LastPass and KeePass. Password managers make it very convenient for users to use a unique, strong password for each service that requires password authentication. However, given the sensitivity of the data contained in the password manager, it takes considerable care to store the information securely. In this assignment, you will be writing a secure and efficient password manager. In your implemen- tation, you will make use of various cryptographic primitives we have discussed in class—notably, authenticated encryption and collision-resistant hash functions. Because it is ill-advised to imple- ment your own primitives in cryptography, you should use an established library: in this case, the Stanford Javascript Crypto Library (SJCL). We will provide starter code that contains a basic tem- plate, which you will be able to fill in to satisfy the functionality and security properties described below. -
Internet Security Threat Report Volume 24 | February 2019
ISTRInternet Security Threat Report Volume 24 | February 2019 THE DOCUMENT IS PROVIDED “AS IS” AND ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE DISCLAIMED, EXCEPT TO THE EXTENT THAT SUCH DISCLAIMERS ARE HELD TO BE LEGALLY INVALID. SYMANTEC CORPORATION SHALL NOT BE LIABLE FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES IN CONNECTION WITH THE FURNISHING, PERFORMANCE, OR USE OF THIS DOCUMENT. THE INFORMATION CONTAINED IN THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. INFORMATION OBTAINED FROM THIRD PARTY SOURCES IS BELIEVED TO BE RELIABLE, BUT IS IN NO WAY GUARANTEED. SECURITY PRODUCTS, TECHNICAL SERVICES, AND ANY OTHER TECHNICAL DATA REFERENCED IN THIS DOCUMENT (“CONTROLLED ITEMS”) ARE SUBJECT TO U.S. EXPORT CONTROL AND SANCTIONS LAWS, REGULATIONS AND REQUIREMENTS, AND MAY BE SUBJECT TO EXPORT OR IMPORT REGULATIONS IN OTHER COUNTRIES. YOU AGREE TO COMPLY STRICTLY WITH THESE LAWS, REGULATIONS AND REQUIREMENTS, AND ACKNOWLEDGE THAT YOU HAVE THE RESPONSIBILITY TO OBTAIN ANY LICENSES, PERMITS OR OTHER APPROVALS THAT MAY BE REQUIRED IN ORDER FOR YOU TO EXPORT, RE-EXPORT, TRANSFER IN COUNTRY OR IMPORT SUCH CONTROLLED ITEMS. TABLE OF CONTENTS 1 2 3 BIG NUMBERS YEAR-IN-REVIEW FACTS AND FIGURES METHODOLOGY Formjacking Messaging Cryptojacking Malware Ransomware Mobile Living off the land Web attacks and supply chain attacks Targeted attacks Targeted attacks IoT Cloud Underground economy IoT Election interference MALICIOUS -
Chapter 3 – Block Ciphers and the Data Encryption Standard
Chapter 3 –Block Ciphers and the Data Cryptography and Network Encryption Standard Security All the afternoon Mungo had been working on Stern's Chapter 3 code, principally with the aid of the latest messages which he had copied down at the Nevin Square drop. Stern was very confident. He must be well aware London Central knew about that drop. It was obvious Fifth Edition that they didn't care how often Mungo read their messages, so confident were they in the by William Stallings impenetrability of the code. —Talking to Strange Men, Ruth Rendell Lecture slides by Lawrie Brown Modern Block Ciphers Block vs Stream Ciphers now look at modern block ciphers • block ciphers process messages in blocks, each one of the most widely used types of of which is then en/decrypted cryptographic algorithms • like a substitution on very big characters provide secrecy /hii/authentication services – 64‐bits or more focus on DES (Data Encryption Standard) • stream ciphers process messages a bit or byte at a time when en/decrypting to illustrate block cipher design principles • many current ciphers are block ciphers – better analysed – broader range of applications Block vs Stream Ciphers Block Cipher Principles • most symmetric block ciphers are based on a Feistel Cipher Structure • needed since must be able to decrypt ciphertext to recover messages efficiently • bloc k cihiphers lklook like an extremely large substitution • would need table of 264 entries for a 64‐bit block • instead create from smaller building blocks • using idea of a product cipher 1 Claude -
Fast Hashing and Stream Encryption with Panama
Fast Hashing and Stream Encryption with Panama Joan Daemen1 and Craig Clapp2 1 Banksys, Haachtesteenweg 1442, B-1130 Brussel, Belgium [email protected] 2 PictureTel Corporation, 100 Minuteman Rd., Andover, MA 01810, USA [email protected] Abstract. We present a cryptographic module that can be used both as a cryptographic hash function and as a stream cipher. High performance is achieved through a combination of low work-factor and a high degree of parallelism. Throughputs of 5.1 bits/cycle for the hashing mode and 4.7 bits/cycle for the stream cipher mode are demonstrated on a com- mercially available VLIW micro-processor. 1 Introduction Panama is a cryptographic module that can be used both as a cryptographic hash function and a stream cipher. It is designed to be very efficient in software implementations on 32-bit architectures. Its basic operations are on 32-bit words. The hashing state is updated by a parallel nonlinear transformation, the buffer operates as a linear feedback shift register, similar to that applied in the compression function of SHA [6]. Panama is largely based on the StepRightUp stream/hash module that was described in [4]. Panama has a low per-byte work factor while still claiming very high security. The price paid for this is a relatively high fixed computational overhead for every execution of the hash function. This makes the Panama hash function less suited for the hashing of messages shorter than the equivalent of a typewritten page. For the stream cipher it results in a relatively long initialization procedure. Hence, in applications where speed is critical, too frequent resynchronization should be avoided. -
User Authentication and Cryptographic Primitives
User Authentication and Cryptographic Primitives Brad Karp UCL Computer Science CS GZ03 / M030 16th November 2016 Outline • Authenticating users – Local users: hashed passwords – Remote users: s/key – Unexpected covert channel: the Tenex password- guessing attack • Symmetric-key-cryptography • Public-key cryptography usage model • RSA algorithm for public-key cryptography – Number theory background – Algorithm definition 2 Dictionary Attack on Hashed Password Databases • Suppose hacker obtains copy of password file (until recently, world-readable on UNIX) • Compute H(x) for 50K common words • String compare resulting hashed words against passwords in file • Learn all users’ passwords that are common English words after only 50K computations of H(x)! • Same hashed dictionary works on all password files in world! 3 Salted Password Hashes • Generate a random string of bytes, r • For user password x, store [H(r,x), r] in password file • Result: same password produces different result on every machine – So must see password file before can hash dictionary – …and single hashed dictionary won’t work for multiple hosts • Modern UNIX: password hashes salted; hashed password database readable only by root 4 Salted Password Hashes • Generate a random string of bytes, r Dictionary• For user password attack still x, store possible [H(r,x after), r] in attacker seespassword password file file! Users• Result: should same pick password passwords produces that different aren’t result close to ondictionary every machine words. – So must see password file -
Related-Key Cryptanalysis of 3-WAY, Biham-DES,CAST, DES-X, Newdes, RC2, and TEA
Related-Key Cryptanalysis of 3-WAY, Biham-DES,CAST, DES-X, NewDES, RC2, and TEA John Kelsey Bruce Schneier David Wagner Counterpane Systems U.C. Berkeley kelsey,schneier @counterpane.com [email protected] f g Abstract. We present new related-key attacks on the block ciphers 3- WAY, Biham-DES, CAST, DES-X, NewDES, RC2, and TEA. Differen- tial related-key attacks allow both keys and plaintexts to be chosen with specific differences [KSW96]. Our attacks build on the original work, showing how to adapt the general attack to deal with the difficulties of the individual algorithms. We also give specific design principles to protect against these attacks. 1 Introduction Related-key cryptanalysis assumes that the attacker learns the encryption of certain plaintexts not only under the original (unknown) key K, but also under some derived keys K0 = f(K). In a chosen-related-key attack, the attacker specifies how the key is to be changed; known-related-key attacks are those where the key difference is known, but cannot be chosen by the attacker. We emphasize that the attacker knows or chooses the relationship between keys, not the actual key values. These techniques have been developed in [Knu93b, Bih94, KSW96]. Related-key cryptanalysis is a practical attack on key-exchange protocols that do not guarantee key-integrity|an attacker may be able to flip bits in the key without knowing the key|and key-update protocols that update keys using a known function: e.g., K, K + 1, K + 2, etc. Related-key attacks were also used against rotor machines: operators sometimes set rotors incorrectly. -
Cryptography in Modern World
Cryptography in Modern World Julius O. Olwenyi, Aby Tino Thomas, Ayad Barsoum* St. Mary’s University, San Antonio, TX (USA) Emails: [email protected], [email protected], [email protected] Abstract — Cryptography and Encryption have been where a letter in plaintext is simply shifted 3 places down used for secure communication. In the modern world, the alphabet [4,5]. cryptography is a very important tool for protecting information in computer systems. With the invention ABCDEFGHIJKLMNOPQRSTUVWXYZ of the World Wide Web or Internet, computer systems are highly interconnected and accessible from DEFGHIJKLMNOPQRSTUVWXYZABC any part of the world. As more systems get interconnected, more threat actors try to gain access The ciphertext of the plaintext “CRYPTOGRAPHY” will to critical information stored on the network. It is the be “FUBSWRJUASLB” in a Caesar cipher. responsibility of data owners or organizations to keep More recent derivative of Caesar cipher is Rot13 this data securely and encryption is the main tool used which shifts 13 places down the alphabet instead of 3. to secure information. In this paper, we will focus on Rot13 was not all about data protection but it was used on different techniques and its modern application of online forums where members could share inappropriate cryptography. language or nasty jokes without necessarily being Keywords: Cryptography, Encryption, Decryption, Data offensive as it will take those interested in those “jokes’ security, Hybrid Encryption to shift characters 13 spaces to read the message and if not interested you do not need to go through the hassle of converting the cipher. I. INTRODUCTION In the 16th century, the French cryptographer Back in the days, cryptography was not all about Blaise de Vigenere [4,5], developed the first hiding messages or secret communication, but in ancient polyalphabetic substitution basically based on Caesar Egypt, where it began; it was carved into the walls of cipher, but more difficult to crack the cipher text. -
On the NIST Lightweight Cryptography Standardization
On the NIST Lightweight Cryptography Standardization Meltem S¨onmez Turan NIST Lightweight Cryptography Team ECC 2019: 23rd Workshop on Elliptic Curve Cryptography December 2, 2019 Outline • NIST's Cryptography Standards • Overview - Lightweight Cryptography • NIST Lightweight Cryptography Standardization Process • Announcements 1 NIST's Cryptography Standards National Institute of Standards and Technology • Non-regulatory federal agency within U.S. Department of Commerce. • Founded in 1901, known as the National Bureau of Standards (NBS) prior to 1988. • Headquarters in Gaithersburg, Maryland, and laboratories in Boulder, Colorado. • Employs around 6,000 employees and associates. NIST's Mission to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life. 2 NIST Organization Chart Laboratory Programs Computer Security Division • Center for Nanoscale Science and • Cryptographic Technology Technology • Secure Systems and Applications • Communications Technology Lab. • Security Outreach and Integration • Engineering Lab. • Security Components and Mechanisms • Information Technology Lab. • Security Test, Validation and • Material Measurement Lab. Measurements • NIST Center for Neutron Research • Physical Measurement Lab. Information Technology Lab. • Advanced Network Technologies • Applied and Computational Mathematics • Applied Cybersecurity • Computer Security • Information Access • Software and Systems • Statistical