Implementaç˜Ao Em Software De Algoritmos De Resumo Criptográfico
Total Page：16
File Type：pdf, Size：1020Kb
Load more
Recommended publications
-
Increasing Cryptography Security Using Hash-Based Message
ISSN (Print) : 2319-8613 ISSN (Online) : 0975-4024 Seyyed Mehdi Mousavi et al. / International Journal of Engineering and Technology (IJET) Increasing Cryptography Security using Hash-based Message Authentication Code Seyyed Mehdi Mousavi*1, Dr.Mohammad Hossein Shakour 2 1-Department of Computer Engineering, Shiraz Branch, Islamic AzadUniversity, Shiraz, Iran . Email : [email protected] 2-Assistant Professor, Department of Computer Engineering, Shiraz Branch, Islamic Azad University ,Shiraz ,Iran Abstract Nowadays, with the fast growth of information and communication technologies (ICTs) and the vulnerabilities threatening human societies, protecting and maintaining information is critical, and much attention should be paid to it. In the cryptography using hash-based message authentication code (HMAC), one can ensure the authenticity of a message. Using a cryptography key and a hash function, HMAC creates the message authentication code and adds it to the end of the message supposed to be sent to the recipient. If the recipient of the message code is the same as message authentication code, the packet will be confirmed. The study introduced a complementary function called X-HMAC by examining HMAC structure. This function uses two cryptography keys derived from the dedicated cryptography key of each packet and the dedicated cryptography key of each packet derived from the main X-HMAC cryptography key. In two phases, it hashes message bits and HMAC using bit Swapp and rotation to left. The results show that X-HMAC function can be a strong barrier against data identification and HMAC against the attacker, so that it cannot attack it easily by identifying the blocks and using HMAC weakness. -
CHAPTER 9: ANALYSIS of the SHA and SHA-L HASH ALGORITHMS
CHAPTER 9: ANALYSIS OF THE SHA AND SHA-l HASH ALGORITHMS In this chapter the SHA and SHA-l hash functions are analysed. First the SHA and SHA-l hash functions are described along with the relevant notation used in this chapter. This is followed by describing the algebraic structure of the message expansion algorithm used by SHA. We then proceed to exploit this algebraic structure of the message expansion algorithm by applying the generalised analysis framework presented in Chapter 8. We show that it is possible to construct collisions for each of the individual rounds of the SHA hash function. The source code that implements the attack is attached in Appendix F. The same techniques are then applied to SHA-l. SHA is an acronym for Secure Hash Algorithm. SHA and SHA-l are dedicated hash func- tions based on the iterative Damgard-Merkle construction [22] [23]. Both of the round func- tions utilised by these algorithms take a 512 bit input (or a multiple of 512) and produce a 160 bit hash value. SHA was first published as Federal Information Processing Standard 180 (FIPS 180). The secure hash algorithm is based on principles similar to those used in the design of MD4 [10]. SHA-l is a technical revision of SHA and was published as FIPS 180-1 [13]. It is believed that this revision makes SHA-l more secure than SHA [13] [50] [59]. SHA and SHA-l differ from MD4 with regard to the number of rounds used, the size of the hash result and the definition of a single step. -
(1) Hash Functions (2) MAC MDC OWHF CRHF UOWHF
Hash functions (1) are secure; they can be reduced to @ @ 2 classes based on linear transfor- @ @ mations of variables. The properties @ of these 12 schemes with respect to @ @ Hash Functions: Past, Present and Future weaknesses of the underlying block @ @ cipher are studied. The same ap- proach can be extended to study keyed hash functions (MACs) based - -63102392168 on block ciphers and hash functions h Bart Preneel based on modular arithmetic. Fi- nally a new attack is presented on a scheme suggested by R. Merkle. Katholieke Universiteit Leuven This slide is now shown at the Asi- acrypt 2005 in the beautiful city of bartDOTpreneel(AT)esatDOTkuleuvenDOTbe Chennai during a presentation on the state of hash functions. http://homes.esat.kuleuven.be/ preneel ∼ 5 December 2005 3 Outline Hash functions (2) Definitions • cryptographic hash function Z Z Applications Z Z • Z Z General Attacks = ZZ~ • MAC MDC Constructions @ @ • @ @ Custom Designed Hash Functions @ • © @R Hash Functions Based on Block Ciphers OWHF ? CRHF • Hash Functions Based on Algebraic Operations UOWHF • Pseudo-randomness • This talk: only MDCs (Manipulation Detection Codes), which are Conclusions often called `hash functions' • 2 4 Informal definitions (1) Informal definitions (3) preimage resistant 2nd preimage resistant 6) take a preimage resistant hash function; add an input bit b and • replace one input bit by the sum modulo 2 of this input bit and b 2nd preimage resistant preimage resistant 6) if h is OWHF, h is 2nd preimage resistant but not preimage • resistant -
MD5 Collisions the Effect on Computer Forensics April 2006
Paper MD5 Collisions The Effect on Computer Forensics April 2006 ACCESS DATA , ON YOUR RADAR MD5 Collisions: The Impact on Computer Forensics Hash functions are one of the basic building blocks of modern cryptography. They are used for everything from password verification to digital signatures. A hash function has three fundamental properties: • It must be able to easily convert digital information (i.e. a message) into a fixed length hash value. • It must be computationally impossible to derive any information about the input message from just the hash. • It must be computationally impossible to find two files to have the same hash. A collision is when you find two files to have the same hash. The research published by Wang, Feng, Lai and Yu demonstrated that MD5 fails this third requirement since they were able to generate two different messages that have the same hash. In computer forensics hash functions are important because they provide a means of identifying and classifying electronic evidence. Because hash functions play a critical role in evidence authentication, a judge and jury must be able trust the hash values to uniquely identify electronic evidence. A hash function is unreliable when you can find any two messages that have the same hash. Birthday Paradox The easiest method explaining a hash collision is through what is frequently referred to as the Birthday Paradox. How many people one the street would you have to ask before there is greater than 50% probability that one of those people will share your birthday (same day not the same year)? The answer is 183 (i.e. -
Design Principles for Hash Functions Revisited
Design Principles for Hash Functions Revisited Bart Preneel Katholieke Universiteit Leuven, COSIC bartDOTpreneel(AT)esatDOTkuleuvenDOTbe http://homes.esat.kuleuven.be/ preneel � October 2005 Outline Definitions • Generic Attacks • Constructions • A Comment on HMAC • Conclusions • are secure; they can be reduced to @ @ 2 classes based on linear transfor @ @ mations of variables. The properties @ of these 12 schemes with respect to @ @ weaknesses of the underlying block @ @ cipher are studied. The same ap proach can be extended to study keyed hash functions (MACs) based - -63102392168 on block ciphers and hash functions h based on modular arithmetic. Fi nally a new attack is presented on a scheme suggested by R. Merkle. This slide is now shown at the VI Spanish meeting on Information Se curity and Cryptology in a presenta tion on the state of hash functions. 2 Informal definitions (1) no secret parameters • x arbitrary length fixed length n • ) computation “easy” • One Way Hash Function (OWHF): preimage resistant: ! h(x) x with h(x) = h(x ) • 6) 0 0 2nd preimage resistant: • ! x; h(x) x (= x) with h(x ) = h(x) 6) 0 6 0 Collision Resistant Hash Function (CRHF) = OWHF + collision resistant: • x, x (x = x) with h(x) = h(x ). 6) 0 0 6 0 3 Informal definitions (2) preimage resistant 2nd preimage resistant 6) take a preimage resistant hash function; add an input bit b and • replace one input bit by the sum modulo 2 of this input bit and b 2nd preimage resistant preimage resistant 6) if h is OWHF, h is 2nd preimage resistant but not preimage • resistant 0 X if X n h(X) = 1kh(X) otherwise.j j < ( k collision resistant 2nd preimage resistant ) [Simon 98] one cannot derive collision resistance from ‘general’ preimage resistance 4 Formal definitions: (2nd) preimage resistance Notation: L = 0; 1 , l(n) > n f g A one-way hash function H is a function with domain D = Ll(n) and range R = Ln that satisfies the following conditions: preimage resistance: let x be selected uniformly in D and let M • be an adversary that on input h(x) uses time t and outputs < M(h(x)) D. -
Cryptanalysis of Stream Ciphers Based on Arrays and Modular Addition
KATHOLIEKE UNIVERSITEIT LEUVEN FACULTEIT INGENIEURSWETENSCHAPPEN DEPARTEMENT ELEKTROTECHNIEK{ESAT Kasteelpark Arenberg 10, 3001 Leuven-Heverlee Cryptanalysis of Stream Ciphers Based on Arrays and Modular Addition Promotor: Proefschrift voorgedragen tot Prof. Dr. ir. Bart Preneel het behalen van het doctoraat in de ingenieurswetenschappen door Souradyuti Paul November 2006 KATHOLIEKE UNIVERSITEIT LEUVEN FACULTEIT INGENIEURSWETENSCHAPPEN DEPARTEMENT ELEKTROTECHNIEK{ESAT Kasteelpark Arenberg 10, 3001 Leuven-Heverlee Cryptanalysis of Stream Ciphers Based on Arrays and Modular Addition Jury: Proefschrift voorgedragen tot Prof. Dr. ir. Etienne Aernoudt, voorzitter het behalen van het doctoraat Prof. Dr. ir. Bart Preneel, promotor in de ingenieurswetenschappen Prof. Dr. ir. Andr´eBarb´e door Prof. Dr. ir. Marc Van Barel Prof. Dr. ir. Joos Vandewalle Souradyuti Paul Prof. Dr. Lars Knudsen (Technical University, Denmark) U.D.C. 681.3*D46 November 2006 ⃝c Katholieke Universiteit Leuven { Faculteit Ingenieurswetenschappen Arenbergkasteel, B-3001 Heverlee (Belgium) Alle rechten voorbehouden. Niets uit deze uitgave mag vermenigvuldigd en/of openbaar gemaakt worden door middel van druk, fotocopie, microfilm, elektron- isch of op welke andere wijze ook zonder voorafgaande schriftelijke toestemming van de uitgever. All rights reserved. No part of the publication may be reproduced in any form by print, photoprint, microfilm or any other means without written permission from the publisher. D/2006/7515/88 ISBN 978-90-5682-754-0 To my parents for their unyielding ambition to see me educated and Prof. Bimal Roy for making cryptology possible in my life ... My Gratitude It feels awkward to claim the thesis to be singularly mine as a great number of people, directly or indirectly, participated in the process to make it see the light of day. -
Security of VSH in the Real World
Security of VSH in the Real World Markku-Juhani O. Saarinen Information Security Group Royal Holloway, University of London Egham, Surrey TW20 0EX, UK. [email protected] Abstract. In Eurocrypt 2006, Contini, Lenstra, and Steinfeld proposed a new hash function primitive, VSH, very smooth hash. In this brief paper we offer com- mentary on the resistance of VSH against some standard cryptanalytic attacks, in- cluding preimage attacks and collision search for a truncated VSH. Although the authors of VSH claim only collision resistance, we show why one must be very careful when using VSH in cryptographic engineering, where additional security properties are often required. 1 Introduction Many existing cryptographic hash functions were originally designed to be message di- gests for use in digital signature schemes. However, they are also often used as building blocks for other cryptographic primitives, such as pseudorandom number generators (PRNGs), message authentication codes, password security schemes, and for deriving keying material in cryptographic protocols such as SSL, TLS, and IPSec. These applications may use truncated versions of the hashes with an implicit as- sumption that the security of such a variant against attacks is directly proportional to the amount of entropy (bits) used from the hash result. An example of this is the HMAC−n construction in IPSec [1]. Some signature schemes also use truncated hashes. Hence we are driven to the following slightly nonstandard definition of security goals for a hash function usable in practice: 1. Preimage resistance. For essentially all pre-specified outputs X, it is difficult to find a message Y such that H(Y ) = X. -
The First Cryptographic Hash Workshop
Workshop Report The First Cryptographic Hash Workshop Gaithersburg, MD Oct. 31-Nov. 1, 2005 Report prepared by Shu-jen Chang and Morris Dworkin Information Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 Available online: http://csrc.nist.gov/groups/ST/hash/documents/HashWshop_2005_Report.pdf 1. Introduction On Oct. 31-Nov. 1, 2005, 180 members of the global cryptographic community gathered in Gaithersburg, MD to attend the first Cryptographic Hash Workshop. The workshop was organized in response to a recent attack on the NIST-approved Secure Hash Algorithm SHA-1. The purpose of the workshop was to discuss this attack, assess the status of other NIST-approved hash algorithms, and discuss possible near-and long-term options. 2. Workshop Program The workshop program consisted of two days of presentations of papers that were submitted to the workshop and panel discussion sessions that NIST organized. The main topics for the discussions included the SHA-1 and SHA-2 hash functions, future research of hash functions, and NIST’s strategy. The program is available at http://csrc.nist.gov/groups/ST/hash/first_workshop.html. This report only briefly summarizes the presentations, because the above web site for the program includes links to the speakers' slides and papers. The main ideas of the discussion sessions, however, are described in considerable detail; in fact, the panelists and attendees are often paraphrased very closely, to minimize misinterpretation. Their statements are not necessarily presented in the order that they occurred, in order to organize them according to NIST's questions for each session. 3. -
The Whirlpool Secure Hash Function
Cryptologia, 30:55–67, 2006 Copyright Taylor & Francis Group, LLC ISSN: 0161-1194 print DOI: 10.1080/01611190500380090 The Whirlpool Secure Hash Function WILLIAM STALLINGS Abstract In this paper, we describe Whirlpool, which is a block-cipher-based secure hash function. Whirlpool produces a hash code of 512 bits for an input message of maximum length less than 2256 bits. The underlying block cipher, based on the Advanced Encryption Standard (AES), takes a 512-bit key and oper- ates on 512-bit blocks of plaintext. Whirlpool has been endorsed by NESSIE (New European Schemes for Signatures, Integrity, and Encryption), which is a European Union-sponsored effort to put forward a portfolio of strong crypto- graphic primitives of various types. Keywords advanced encryption standard, block cipher, hash function, sym- metric cipher, Whirlpool Introduction In this paper, we examine the hash function Whirlpool [1]. Whirlpool was developed by Vincent Rijmen, a Belgian who is co-inventor of Rijndael, adopted as the Advanced Encryption Standard (AES); and by Paulo Barreto, a Brazilian crypto- grapher. Whirlpool is one of only two hash functions endorsed by NESSIE (New European Schemes for Signatures, Integrity, and Encryption) [13].1 The NESSIE project is a European Union-sponsored effort to put forward a portfolio of strong cryptographic primitives of various types, including block ciphers, symmetric ciphers, hash functions, and message authentication codes. Background An essential element of most digital signature and message authentication schemes is a hash function. A hash function accepts a variable-size message M as input and pro- duces a fixed-size hash code HðMÞ, sometimes called a message digest, as output. -
A Fast New Cryptographic Hash Function Based on Integer Tent Mapping System
JOURNAL OF COMPUTERS, VOL. 7, NO. 7, JULY 2012 1671 A Fast New Cryptographic Hash Function Based on Integer Tent Mapping System Jiandong Liu Information Engineering College, Beijing Institute of Petrochemical Technology, Beijing, China [email protected] Xiahui Wang, Kai Yang, Chen Zhao Information Engineering College, Beijing Institute of Petrochemical Technology, Beijing, China {Wnagxiahui, Yangkai0212, zhao_chen}@bipt.edu.cn Abstract—This paper proposes a novel one-way Hash collisions by SHA-1” by Wang and Yu is another function which is based on the Coupled Integer Tent breakthrough in the hash functions history [11]. Mapping System and termed as THA (THA-160, THA-256). Based on the MD iteration structure [3], the The THA-160 compresses a message of arbitrary length into conventional Hash functions (MDx and SHA) have many a fingerprint of 160 bits, well the THA-256 compresses a common design guidelines. The designs of their mixed message of arbitrary length into a fingerprint of 256 bits. The algorithm adopts a piecewise message expansion operations for each round are very similar, and all of scheme. Compared with SHA-1 and SHA-256 message them adopt integer modulo addition and logic function; expansion, the message expansion scheme has enhanced the therefore, many Hash functions have been breached degree of nonlinear diffusion of the message expansion, and successively within a short period of time, which thus increased the computation efficiency. In addition, as indicates the defects in the design of the Hash functions. the major nonlinear component of compression function, the In recent years, in order to obtain more secure hash traditional logic functions are replaced by the integer tent functions, the research on constructing one-way hash map, and so the scheme has ideal properties of diffusion and function has been carried out and it has achieved progress confusion. -
LNCS 3494, Pp
Cryptanalysis of the Hash Functions MD4 and RIPEMD Xiaoyun Wang1, Xuejia Lai2, Dengguo Feng3, Hui Chen1, and Xiuyuan Yu4 1 Shandong University, Jinan250100, China [email protected] 2 Shanghai Jiaotong University, Shanghai200052, China 3 Chinese Academy of Science China, Beijing100080, China 4 Huangzhou Teacher College, Hangzhou310012, China Abstract. MD4 is a hash function developed by Rivest in 1990. It serves as the basis for most of the dedicated hash functions such as MD5, SHAx, RIPEMD, and HAVAL. In 1996, Dobbertin showed how to find collisions of MD4 with complexity equivalent to 220 MD4 hash computations. In this paper, we present a new attack on MD4 which can find a collision with probability 2−2 to 2−6, and the complexity of finding a collision doesn’t exceed 28 MD4 hash operations. Built upon the collision search attack, we present a chosen-message pre-image attack on MD4 with com- plexity below 28. Furthermore, we show that for a weak message, we can find another message that produces the same hash value. The complex- ity is only a single MD4 computation, and a random message is a weak message with probability 2−122. The attack on MD4 can be directly applied to RIPEMD which has two parallel copies of MD4, and the complexity of finding a collision is about 218 RIPEMD hash operations. 1 Introduction MD4 [14] is an early-appeared hash function that is designed using basic arith- metic and Boolean operations that are readily available on modern computers. Such type of hash functions are often referred to as dedicated hash functions, and they are quite different from hash functions based on block ciphers. -
Block Cipher Based Hashed Functions
ANALYSIS OF THREE BLOCK CIPHER BASED HASH FUNCTIONS: WHIRLPOOL, GRØSTL AND GRINDAHL A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF APPLIED MATHEMATICS OF MIDDLE EAST TECHNICAL UNIVERSITY BY RITA ISMAILOVA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHYLOSOPHY IN CRYPTOGRAPHY SEPTEMBER 2012 Approval of the thesis: ANALYSIS OF THREE BLOCK CIPHER BASED HASH FUNCTIONS: WHIRLPOOL, GRØSTL AND GRINDAHL submitted by RITA ISMAILOVA in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Department of Cryptography, Middle East Technical University by, Prof. Dr. Bülent Karasözen ____________ Director, Graduate School of Applied Mathematics Prof. Dr. Ferruh Özbudak ____________ Head of Department, Cryptography Assoc. Prof. Dr. Melek Diker Yücel ____________ Supervisor, Department of Electrical and Electronics Engineering Examining Committee Members: Prof. Dr. Ersan Akyıldız ____________ Department of Mathematics, METU Assoc. Prof. Dr. Melek Diker Yücel ____________ Department of Electrical and Electronics Engineering, METU Assoc. Prof. Dr. Ali Doğanaksoy ____________ Department of Mathematics, METU Assist. Prof. Dr. Zülfükar Saygı ____________ Department of Mathematics, TOBB ETU Dr. Hamdi Murat Yıldırım ____________ Department of Computer Technology and Information Systems, Bilkent University Date: ____________ I hereby declare that all information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work. Name, Last Name: RITA ISMAILOVA Signature : iii ABSTRACT ANALYSIS OF THREE BLOCK CIPHER BASED HASH FUNCTIONS: WHIRLPOOL, GRØSTL AND GRINDAHL Ismailova, Rita Ph.D., Department of Cryptography Supervisor : Assoc.