DOCSLIB.ORG

An Analysis and Application of One-Time Pad in a Group

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
An Analysis and Application of One-Time Pad in a Group Eindhoven University of Technology MASTER An analysis and application of one-time pad in a group Zijlstra, A.T. Award date: 2017 Link to publication Disclaimer This document contains a student thesis (bachelor's or master's), as authored by a student at Eindhoven University of Technology. Student theses are made available in the TU/e repository upon obtaining the required degree. The grade received is not published on the document as presented in the repository. The required complexity or quality of research of student theses may vary by program, and the required minimum study period may vary in duration. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain Department of Mathematics and Departamento de Ciência da Computer Science Computação Master’s thesis An analysis and application of One-time Pad in a group by Arjen Teijo Zijlstra Supervisor: dr.ir. L.A.M. (Berry) Schoenmakers External supervisor: prof.dr. J.A.M. (Jeroen) van de Graaf December 23, 2016 Abstract One-time Pad (otp) is a cryptosystem that encrypts a plaintext by taking the ex- clusive or with a key that is the same length as the plaintext, truly random and only used once. Although there are challenges to overcome when using otp, the trend of storage getting cheaper and upcoming Quantum Key Distribution methods make it an interesting system. In this work we extend the analysis on parameters for the Group One-time Pad (gotp) cryptosystem presented in [Gra16]. The gotp cryptosystem applies otp in a group by selecting a certain number of parts from a secret for encryption keys at random. The main result is a heuristic lower bound for the number of parts selected per encryption key. This bound is equal to the natural logarithm of the number of parts available in a secret, where the number of parts selected per encryption key is odd. If we apply this cryptosystem in the Bounded Retrieval Model, this bound increases a lot and depends heavily on the expected amount of leakage. Besides the analysis, we design and implement software for the gotp cryptosys- tem. The implementation is in the form of an open source C++ library freely available at github.com/arjenzijlstra for academic use. i Acknowledgements First of all, I would like to thank dr.ir. Berry Schoenmakers for being my supervisor, for all his effort and time he put in, and the many useful ideas and remarks on my work he provided. Furthermore, I would like to thank prof.dr. Jeroen van de Graaf for all his feedback and ideas and for giving me the chance to come to Brazil to work on this project, while learning about the language and culture in the country. E, claro, quero agradecer aos meus amigos Brasileiros e internacionais por toda a ajuda e por terem me proporcionado um período incrível no Brasil. Muito obrigado a vocês. And finally, I would like to thank all my family, friends and fellow students in the Netherlands for always being there for me and for the feedback you guys gave me. Arjen Teijo Zijlstra Belo Horizonte & Eindhoven, December 2016. ii Table of Contents Abstract i Acknowledgements ii 1 Introduction 1 1.1 Related work . 2 2 One-time Pad in a group 4 2.1 Traditional One-time Pad . 4 2.2 Group Usage . 6 2.2.1 Towards Group One-time Pad . 7 2.2.2 Group One-time Pad . 9 2.2.3 On Collisions and Dependencies . 10 2.3 Quantitative analysis . 11 2.3.1 Probability of collisions . 11 2.3.2 Random Matrices . 12 2.3.3 Sparse Binary Matrices . 13 2.4 Block Size and Secret Size . 19 2.5 Maximise Utilisation of a Secret . 20 2.5.1 Broadcast . 20 2.5.2 Byzantine Generals . 22 2.5.3 Ostrich Tactic . 23 3 Bounded Retrieval Model 25 3.1 Background . 25 3.2 Big-key Cryptography . 26 3.2.1 Subkey Prediction . 27 3.2.2 Authenticated Encryption . 28 3.2.3 Comparison to Group OTP . 28 iii iv Table of Contents 3.3 Group OTP in the brm ......................... 29 4 Extensions to GOTP 33 4.1 Seeded Key Selection . 33 4.2 Shorter Secrets . 34 4.2.1 Sponge Construction . 34 4.2.2 Randomly Accessible Pseudo Random Generator . 35 4.3 Authenticated Encryption . 35 5 High-level design 38 5.1 Use Case View . 38 5.1.1 Encrypt Message . 39 5.1.2 Decrypt Message . 40 5.1.3 Import Secret . 40 5.1.4 Export Secret . 41 5.2 Logical View . 41 5.2.1 Secret . 42 5.2.2 Text . 45 5.2.3 Cipher . 47 5.2.4 Key Selector . 48 6 Findings and Future Work 50 6.1 Conclusions . 50 6.2 Future Work . 51 References 52 A Simulations A1 B Source Code B1 C Requirements C1 Chapter 1 Introduction Traditionally, symmetric encryption methods protect a plaintext message by encrypt- ing it with a small secret and sharing this small secret over a secure channel, while sharing the large encrypted plaintext over a public channel. One-time Pad (otp) protects a plaintext by encrypting it with a secret equally as large as the plaintext, which is not any easier to share. Probably the most quoted text in discussions about One-time Pad is: “What a one-time pad system does is take a difficult message security problem and turn it into a just-as-difficult key distribution problem.” – Bruce Schneier [Sch02] The point is clear: distributing a large otp secret in a secure way poses a chal- lenge. However, there are specific situations in which using otp could be practical and provide the level of security that is desirable. People who meet on a regular basis but who also want to communicate their thoughts over the internet, without surveil- lance agencies being able to listen in, could share a large secret using SD cards, USB keys or hard drives when they meet and use this secret at a later time to encrypt their communication. Communication produced by and sent between people who meet regularly mostly consist of chat messages, emails or small files, all of which use very little storage. Therefore, a large otp secret will be consumed slowly and exchanging a new secret is only necessary after quite some time, depending on its size and the number of people making use of the same secret. The most important asset of otp is that it is not based on mathematically hard 1 2 1.1. Related work problems and currently the only perfectly secure cryptosystem. The security of otp is based on the requirement that each bit of the otp secret is only used once, which in combination with its randomness results in a ciphertext on which cryptanalysis is impossible. Its perfect security makes otp a good system to use for encrypting communication that consists of small messages. However, to be able to use otp there are some hurdles to overcome. Key dis- tribution is not the only challenge of otp; other disadvantages include message authentication, lack of randomness and prevention of reusing encryption keys. The focus of this thesis is on prevention of reusing encryption keys. It is assumed that methods for generating random bits exist and therefore randomness will not be part of this work. Message authentication will be briefly discussed. When using otp between at most two parties, it is easy to avoid using the same part of the otp secret for encrypting two different messages. However, problems arise when dealing with a group of people that work together and want to use otp. Either a separate secret must be shared for each direction of encryption or a smarter way of managing encryption keys is needed. The option to share an otp secret between every pair of persons will rapidly result in many secrets that must be shared and stored securely, which is not feasible when using very large otp secrets. Assuming that a group is based on mutual trust, all members could make use of the same secret to derive keys from for encrypting their communication, but we have to make sure that no part of the secret is ever used twice. The goal of this work is to find a solution for securely applying One-time Pad in a group. From now on the concept will be referred to as Group otp or gotp. In this work we extend the analysis on parameters for the gotp cryptosystem presented in [Gra16]. Furthermore, we compare the gotp cryptosystem to big-key cryptog- raphy presented in [BKR16] and analyse the applicability of gotp in the Bounded Retrieval Model. Finally, we design and implement the system in the form of an open source C++ library. 1.1 Related work Only little work has been performed on the use of one large secret shared between a group of parties, therefore we look at a broader spectrum of methods that make use Chapter 1. Introduction 3 of otp. In [Hal06] a method that makes use of the otp system is presented. They use a random number table, generated by concatenating random numbers, at its base.
Load more

Recommended publications
  • Topic 3: One-Time Pad and Perfect Secrecy
    Cryptography CS 555 Topic 3: One-time Pad and Perfect Secrecy CS555 Spring 2012/Topic 3 1 Outline and Readings • Outline • One-time pad • Perfect secrecy • Limitation of perfect secrecy • Usages of one-time pad • Readings: • Katz and Lindell: Chapter 2 CS555 Spring 2012/Topic 3 2 One-Time Pad • Fix the vulnerability of the Vigenere cipher by using very long keys • Key is a random string that is at least as long as the plaintext • Encryption is similar to shift cipher • Invented by Vernam in the 1920s CS555 Spring 2012/Topic 3 3 One-Time Pad Let Zm ={0,1,…,m-1} be the alphabet. Plaintext space = Ciphtertext space = Key space = n (Zm) The key is chosen uniformly randomly Plaintext X = (x1 x2 … xn) Key K = (k1 k2 … kn) Ciphertext Y = (y1 y2 … yn) ek(X) = (x1+k1 x2+k2 … xn+kn) mod m dk(Y) = (y1-k1 y2-k2 … yn-kn) mod m CS555 Spring 2012/Topic 3 4 The Binary Version of One-Time Pad Plaintext space = Ciphtertext space = Keyspace = {0,1}n Key is chosen randomly For example: • Plaintext is 11011011 • Key is 01101001 • Then ciphertext is 10110010 CS555 Spring 2012/Topic 3 5 Bit Operators • Bit AND 0 0 = 0 0 1 = 0 1 0 = 0 1 1 = 1 • Bit OR 0 0 = 0 0 1 = 1 1 0 = 1 1 1 = 1 • Addition mod 2 (also known as Bit XOR) 0 0 = 0 0 1 = 1 1 0 = 1 1 1 = 0 • Can we use operators other than Bit XOR for binary version of One-Time Pad? CS555 Spring 2012/Topic 3 6 How Good is One-Time Pad? • Intuitively, it is secure … – The key is random, so the ciphertext is completely random • How to formalize the confidentiality requirement? – Want to say “certain thing” is not learnable by the adversary (who sees the ciphertext).
    [Show full text]
  • Applications of SKREM-Like Symmetric Key Ciphers
    Applications of SKREM-like symmetric key ciphers Mircea-Adrian Digulescu1;2 February 2021 1Individual Researcher, Worldwide 2Formerly: Department of Computer Science, Faculty of Mathematics and Computer Science, University of Bucharest, Romania [email protected], [email protected], [email protected] Abstract In a prior paper we introduced a new symmetric key encryption scheme called Short Key Random Encryption Machine (SKREM), for which we claimed excellent security guarantees. In this paper we present and briey discuss some of its applications outside conventional data encryption. These are Secure Coin Flipping, Cryptographic Hashing, Zero-Leaked-Knowledge Authentication and Autho- rization and a Digital Signature scheme which can be employed on a block-chain. We also briey recap SKREM-like ciphers and the assumptions on which their security are based. The above appli- cations are novel because they do not involve public key cryptography. Furthermore, the security of SKREM-like ciphers is not based on hardness of some algebraic operations, thus not opening them up to specic quantum computing attacks. Keywords: Symmetric Key Encryption, Provable Security, One Time Pad, Zero Knowledge, Cryptographic Commit Protocol, Secure Coin Flipping, Authentication, Authorization, Cryptographic Hash, Digital Signature, Chaos Machine 1 Introduction So far, most encryption schemes able to serve Secure Coin Flipping, Zero-Knowledge Authentication and Digital Signatures, have relied on public key cryptography, which in turn relies on the hardness of prime factorization or some algebraic operation in general. Prime Factorization, in turn, has been shown to be vulnerable to attacks by a quantum computer (see [1]). In [2] we introduced a novel symmetric key encryption scheme, which does not rely on hardness of algebraic operations for its security guarantees.
    [Show full text]
  • NIST SP 800-56: Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Superseded)
    ARCHIVED PUBLICATION The attached publication, NIST Special Publication 800-56 (dated July 2005), has been superseded and is provided here only for historical purposes. For the most current revision of this publication, see: http://csrc.nist.gov/publications/PubsSPs.html#800-56A. NIST Special Publication 800-56 Recommendation for Pair-Wise July 2005 Key Establishment Schemes Using Discrete Logarithm Cryptography Elaine Barker, Don Johnson, and Miles Smid C O M P U T E R S E C U R I T Y NIST SP 800-56: Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography DRAFT July 2005 DRAFT Abstract This Recommendation specifies key establishment schemes using discrete logarithm cryptography, based on standards developed by the Accredited Standards Committee (ASC) X9, Inc.: ANS X9.42 (Agreement of Symmetric Keys Using Discrete Logarithm Cryptography) and ANS X9.63 (Key Agreement and Key Transport Using Elliptic Curve Cryptography). Worked examples are provided in Appendix D. KEY WORDS: assurances; Diffie-Hellman; elliptic curve cryptography; finite field cryptography; key agreement; key confirmation; key derivation; key establishment; key management; MQV. 2 NIST SP 800-56: Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography DRAFT July 2005 DRAFT Acknowledgements The National Institute of Standards and Technology (NIST) gratefully acknowledges and appreciates contributions by Rich Davis, Mike Hopper and Laurie Law from the National Security Agency concerning the many security
    [Show full text]
  • Public Key Infrastructure (PKI)
    Public Key Infrastructure Public Key Infrastructure (PKI) Neil F. Johnson [email protected] http://ise.gmu.edu/~csis Assumptions • Understanding of – Fundamentals of Public Key Cryptosystems – Hash codes for message digests and integrity check – Digital Signatures Copyright 1999, Neil F. Johnson 1 Public Key Infrastructure Overview • Public Key Cryptosystems – Quick review – Cryptography – Digital Signatures – Key Management Issues • Certificates – Certificates Information – Certificate Authority – Track Issuing a Certificate • Putting it all together – PKI applications – Pretty Good Privacy (PGP) – Privacy Enhanced Mail (PEM) Public Key Cryptosystems – Quick Review • Key distribution problem of secret key systems – You must share the secret key with another party before you can initiate communication – If you want to communicate with n parties, you require n different keys • Public Key cryptosystems solve the key distribution problem in secret key systems (provided a reliable channel for communication of public keys can be implemented) • Security is based on the unfeasibility of computing B’s private key given the knowledge of – B’s public key, – chosen plaintext, and – maybe chosen ciphertext Copyright 1999, Neil F. Johnson 2 Public Key Infrastructure Key Distribution (n)(n-1) 2 Bob Bob Alice 1 Alice 2 Chris Chris 7 5 8 9 Ellie 3 Ellie 6 David 4 David Secret Key Distribution Directory of Public Keys (certificates) Public Key Cryptosystem INSECURE CHANNEL Plaintext Ciphertext Plaintext Encryption Decryption Algorithm Algorithm Bob’s PUBLIC
    [Show full text]
  • Introduction, Overview, One Time Pad
    University of Illinois, Urbana Champaign LECTURE CS 598DK Special Topics in Cryptography Instructor: Dakshita Khurana Scribe: Joshua Reynolds, Amit Agarwal Date: August 28, 2019 1 Introduction, Overview, One Time Pad 1.1 Introduction This introductory lecture introduces some fundamental goals of cryptography and defines the basic requirement for a useful private key (symmetric) encryption scheme. A basic problem in Cryptography is that of encryption. The encryption problem is that two parties wish to communicate a message without an eavesdropper being able to learn their secret, or even any information about that secret. This problem can be solved with private key (symmetric) encryption under the assumption that both parties already have a shared secret key. This problem can also be solved with public key (asymmetric) key encryption under various other assumptions. These primitives are among the building blocks of more complicated cryptography sys- tems and a useful medium to explore the assumptions made in cryptographic systems. Encryption, in particular, is important because it allows us to communicate secrets safely through an untrusted medium like the Internet. Focusing first on private key encryption, we define the property of correctness. The second necessary property of encryption is security and is covered in part 2 of these lecture notes. 1.2 Notation This set of scribe notes will use the following notation and definitions: • A set will be denoted by a capital letter { M is the set of all possible messages { K is the set of all possible keys { C is the set of all possible ciphertexts • Set subtraction will use the /operator and jSj means the cardinality of set S • An item from a set will be denoted by a lower case letter { m is a message in plaintext (not encrypted) { ct is a ciphertext (encrypted message) { sk is a secret key used as an input in symmetric encryption and decryption • A statistical method of sampling from a set will be denoted with an arrow combined with a description of how the selection is done.
    [Show full text]
  • Solutions Problem 1. the Ipsec Architecture Documents States That
    Homework 5 - Solutions Problem 1. The IPSec architecture documents states that when two transport mode SA are bundled to allow both AH and ESP protocols on the same end-to-end flow, only one ordering of security protocols seems appropriate: performing the ESP protocol before performing the AH protocol. Why is this approach recommended rather than authentication before encryption? Solution This order of processing facilitates rapid detection and rejection of replayed or bogus packets by the receiver, prior to decrypting the packet, hence potentially reducing the impact of denial of service attacks. It also allows for the possibility of parallel processing of packets at the receiver, i.e., decryption can take place in parallel with authentication. Problem 2. Consider the following threats to web security and describe how each is countered by a particular feature of IPSec. a. Brute force cryptoanalitic attack. An exhaustive search of the key space for a conventional encryption algorithm. b. Known plaintext dictionary. Many messages will have predictable plaintext such as HTTP DET command. An attacker can construct a dictionary containing every possible encryption of the known plaintext message. When an encrypted message is intercepted, the attacker takes the portion containing the encrypted known plaintext and looks up the ciphertext in the dictionary. The ciphertext should match against an entry that was encrypted with the same secret key. This attack is especially effective against small key sizes (e.g. 40-bit keys). c. Replay attack. Earlier SSL handshake messages are replayed. d. Man in the middle. An attacker interposes during key exchange, acting as the client to the server and a server to the client.
    [Show full text]
  • Analysing and Patching SPEKE in ISO/IEC
    1 Analysing and Patching SPEKE in ISO/IEC Feng Hao, Roberto Metere, Siamak F. Shahandashti and Changyu Dong Abstract—Simple Password Exponential Key Exchange reported. Over the years, SPEKE has been used in several (SPEKE) is a well-known Password Authenticated Key Ex- commercial applications: for example, the secure messaging change (PAKE) protocol that has been used in Blackberry on Blackberry phones [11] and Entrust’s TruePass end-to- phones for secure messaging and Entrust’s TruePass end-to- end web products. It has also been included into international end web products [16]. SPEKE has also been included into standards such as ISO/IEC 11770-4 and IEEE P1363.2. In the international standards such as IEEE P1363.2 [22] and this paper, we analyse the SPEKE protocol as specified in the ISO/IEC 11770-4 [24]. ISO/IEC and IEEE standards. We identify that the protocol is Given the wide usage of SPEKE in practical applications vulnerable to two new attacks: an impersonation attack that and its inclusion in standards, we believe a thorough allows an attacker to impersonate a user without knowing the password by launching two parallel sessions with the victim, analysis of SPEKE is both necessary and important. In and a key-malleability attack that allows a man-in-the-middle this paper, we revisit SPEKE and its variants specified in (MITM) to manipulate the session key without being detected the original paper [25], the IEEE 1363.2 [22] and ISO/IEC by the end users. Both attacks have been acknowledged by 11770-4 [23] standards.
    [Show full text]
  • Why Passwords Stink White Paper | Why Passwords Stink
    WHITE PAPER WHY PASSWORDS STINK WHITE PAPER | WHY PASSWORDS STINK 01 INTRODUCTION 02 PASSWORDS ARE FUNDAMENTALLY INSECURE 03 THE PROBLEM WITH PASSWORDS IS THAT THEY CONTENTS ARE “SHARED SECRETS” 04 CURRENT ALTERNATIVES AREN’T THE ANSWER 05 A SOLUTION TO THE PASSWORD ISSUE 06 INTRODUCING BEYOND IDENTITY 07 CONCLUSION 02 WHITE PAPER | WHY PASSWORDS STINK There are hundreds of billions of passwords in the world today, with more being created every day. In fact, the average business user maintains an astounding average of 191 passwords.1 Unfortunately, these passwords represent a fundamentally weak link in most organizations because INTRODUCTION they will always be insecure. This white paper examines why that is, investigates some alternative solutions, and introduces a new method of authentication using asymmetric keys and certificates to eliminate passwords altogether. 01 1 https://www.securitymagazine.com/articles/88475-average-business-user-has-191-passwords 03 WHITE PAPER | WHY PASSWORDS STINK Let’s face it: Passwords stink! For employees and customers, they cause friction and frustration when logging in – Who can remember the 16-character combination of letters, symbols, and digits that are indicative of strong passwords, much less come up with them in the first place? When PASSWORDS ARE a password gets lost or stolen (and they invariably do), it places a burden on the help desk. In fact, 20-50% of help FUNDAMENTALLY desk calls are for password resets, with the average call costing the organization $70.2 INSECURE For CISOs, passwords represent corporate assets that can be targeted by bad actors. And that’s a problem because they often transit networks in the clear, are stored in databases that can be and often are hacked, are shared 02 among colleagues, and are reused across multiple apps – making them easy targets for malware, phishing attacks, and other credential-stealing schemes.
    [Show full text]
  • TCP/IP Network Security
    An Intro to Network Crypto Jim Binkley- [email protected] 1 Crypto outline ◆ overview ◆ symmetric crypto (DES ... encryption) ◆ hash/MAC/message digest algorithms ◆ asymmetric crypto (public key technology) ◆ DH - how to start a secure connection ◆ KDC - a little bit on shared secret servers ◆ signatures - authentication with asymmetric keys ◆ certificates - signed public keys ◆ a little bit on authentication 2 overview ◆ there are MANY crypto algorithms and MANY academic network secure protocols ◆ how they are used in network protocols is another matter ◆ traditional IETF RFC said under security considerations (at end of doc) – “not considered here” (another F. Flub) ◆ new IETF POV: must consider here 3 symmetric encryption ◆ both sides know OUT OF BAND shared secret (password, bit string) ◆ encrypt(key, plaintext) -> cybercrud(encrypted) ◆ decrypt(key, cybercrud) -> plaintext ◆ encode/decode use same key (symmetric) – shared secret on both sides ◆ algorithms include: DES, 3DES, IDEA(128), BLOWFISH, SKIPJACK, new AES ◆ ssh uses 128 bit keyed IDEA ◆ DES key 56 bits - 0xdeadbeefdeadbeef 4 DES-CBC ◆ Cipher Block Chaining Mode ◆ DES processes one 64 bit block of data at a time (key is 64 bits (8 bits not important)) ◆ CBC is used so that e.g., two 64 bit blocks in a row that are the same, do NOT produce two 64 encrypted blocks that are the same ◆ C(n) = Ek [C(n-1) xor Plaintext(n)] ◆ requires known IV or initialization vector 5 pros/cons ◆ pros – faster than asymmetric ◆ cons – shared secrets do not scale in general to many users » more people
    [Show full text]
  • Walking the Bifrost: an Operator's Guide to Heimdal & Kerberos on Macos
    Walking the Bifrost: An Operator's Guide to Heimdal & Kerberos on macOS Cody Thomas Objective By The Sea 3.0 March 2020 WHO AM I? Cody Thomas - @its_a_feature_ ● Operator / Instructor at SpecterOps ● Open Source Developer ○ Apfell – Red Team C2 Framework ○ Bifrost – Kerberos Manipulation ○ Orchard – Open Directory Access ○ GitHub: https://github.com/its-a-feature OVERVIEW ● Brief intro to Kerberos ○ What is it / How does it work / Why do we care? ● Attacking Active Directory Kerberos from macOS ○ Credential Storage / Theft ○ Common Attacks ● Other Kerberos details on macOS ○ LKDC KERBEROS INTRODUCTION A brief overview KERBEROS 101 ● What is Kerberos? ○ Authentication mechanism invented by MIT in 1980s ○ Designed for use on insecure networks ○ Uses math and cryptography to provide strong guarantees ○ Based on a client/server model - stateless ○ Uses ASN.1/DER encoding of data ○ Scoped to ‘realms’ of authentication ● Many implementations ○ Traditional MIT (with plugins) ○ Windows ○ macOS KERBEROS 101 – AUTH STEPS 1. Client and Key Distribution Center (KDC) have shared secret ○ Think of the KDC like an all-knowing PKI management server 2. Client makes a request to the Authentication Server (AS) to be authenticated with the shared secret – i.e. an AS-REQ ○ AS forwards request to the KDC, typically these are the same machine 3. AS responds with a ticket to the krbtgt SPN and encrypts a portion with the krbtgt hash. This ticket is called a Ticket Granting Ticket (TGT). This is an AS-REP. ○ The TGT proves you are who you say you are to the KDC because of the encrypted portion ○ Think of this like a new username/password combination KERBEROS 101 – AUTH STEPS 4.
    [Show full text]
  • On the (Non)Universality of the One-Time Pad
    On the (non)Universality of the One-Time Pad Yevgeniy Dodis Joel Spencer Department of Computer Science Department of Computer Science New York University New York University Email: [email protected] Email: [email protected] Abstract 1 Imperfect Random Sources Randomization is vital in cryptography: secret keys Randomization has proved to be extremely useful and should be randomly generated and most cryptographic fundamental in many areas of computer science, such as primitives (e.g., encryption) must be probabilistic. As a approximation algorithms, counting problems, distributed common abstraction, it is assumed that there is a source of computing, primality testing, as well as cryptographic pro- truly random bits available to all the participants of the sys- tocols (which is the topic of this paper). The common ab- tem. While convenient, this assumption is often highly un- straction used to introduce randomness into computation realistic, and cryptographic systems have to be built based is that the underlying algorithm has access to a stream of on imperfect sources of randomness. Remarkably, this fun- completely unbiased and independent random bits. This ab- damental problem has received little or no attention so far, straction allows one to use randomness in a clean way, sep- despite the fact that a related question of simulating prob- arating out the issue of actually generating such “strong” abilistic (BPP) algorithms with imperfect random sources random bits. Unfortunately, in reality we do not have has a long and rich history. sources that emit perfectly uniform and independent ran- In this work we initiate the quantitative study concerning dom bits.
    [Show full text]
  • Security Policy Trapeze Networks
    MX-200R-GS/MX-216R-GS Mobility Exchange WLAN Controllers Security Policy Trapeze Networks August 14, 2009 Copyright Trapeze Networks 2007. May be reproduced only in its original entirety [without revision]. Security Policy TABLE OF CONTENTS 1. MODULE OVERVIEW .........................................................................................................................................3 2. SECURITY LEVEL................................................................................................................................................4 3. MODES OF OPERATION.....................................................................................................................................5 4. PORTS AND INTERFACES .................................................................................................................................5 5. IDENTIFICATION AND AUTHENTICATION POLICY................................................................................6 6. ACCESS CONTROL POLICY..............................................................................................................................7 ROLES AND SERVICES................................................................................................................................................7 DEFINITION OF CRITICAL SECURITY PARAMETERS (CSPS)........................................................................................7 DEFINITION OF CSPS MODES OF ACCESS ..................................................................................................................8
    [Show full text]