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A Focus on S/MIME
The University of Saskatchewan Department of Computer Science Technical Report #2011-03 Cryptographic Security for Emails: A Focus on S/MIME Minhaz Fahim Zibran Department of Computer Science University of Saskatchewan Email: [email protected] Abstract In this paper I present a study on \S/MIME", which has become the industry standard for secure email exchange. Based on existing literature review, the study examines S/MIME in depth with specific emphasis on its architecture, strengths, and deficiencies. The study also identifies usability issues related to S/MIME enabled email clients, which indicate scopes for further improvements in those implementations. Obstacles in the adoption of S/MIME are also identified indicating what is required for its successful adoption in the community. In presenting the study, the paper contributes in two ways: (a) for any newcomer in the field of cryptography this paper will be a useful resource to quickly learn about S/MIME in a fair level of detail, (b) the indication about limitations of S/MIME and its implementations reveals an avenue for further research in the area of email security, which may result in improvement of S/MIME itself, or its implementations in the email clients. Keywords: Email Security, S/MIME, MIME, PGP, PKI, Certificate, Email Authentication, Email Encryption, Key Management 1 Introduction Email has been a very common medium of communication these days. It somewhat re- places the traditional surface mail and many of the traditional ways of communication [32]. Today people send and read emails from their personal computers, business workstation, PDAs and even cell phones. -
Towards a Hybrid Public Key Infrastructure (PKI): a Review
Towards a Hybrid Public Key Infrastructure (PKI): A Review Priyadarshi Singh, Abdul Basit, N Chaitanya Kumar, and V. Ch. Venkaiah School of Computer and Information Sciences, University of Hyderabad, Hyderabad-500046, India Abstract. Traditional Certificate- based public key infrastructure (PKI) suffers from the problem of certificate overhead like its storage, verification, revocation etc. To overcome these problems, idea of certificate less identity-based public key cryptography (ID-PKC) was proposed by Shamir. This is suitable for closed trusted group only. Also, this concept has some inherent problems like key escrow problem, secure key channel problem, identity management overhead etc. Later on, there had been several works which tried to combine both the cryptographic techniques such that the resulting hybrid PKI framework is built upon the best features of both the cryptographic techniques. It had been shown that this approach solves many problems associated with an individual cryptosystem. In this paper, we have reviewed and compared such hybrid schemes which tried to combine both the certificate based PKC and ID-based PKC. Also, the summary of the comparison, based on various features, is presented in a table. Keywords: Certificate-based PKI; Identity-based public key cryptography (ID-PKC); Hybrid PKI 1 INTRODUCTION Public key infrastructure (PKI) and public key cryptography (PKC) [12] plays a vital role with four major components of digital security: authentication, integrity, confidentiality and non-repudiation. Infact, PKI enables the use of PKC through key management. The ”efficient and secure management of the key pairs during their whole life cycle" is the purpose of PKI, which involves key generation, key distribution, key renewal, key revocation etc [11]. -
Security Target Document
Security Target Document Passport Certificate Server Ver. 4.1.1 Prepared for: Common Criteria EAL2 (augmented) 30 April 2002 2225 Sheppard Ave, Suite 1700 Toronto, Ontario, Canada M2J 5C2 TEL: 416-756-2324 FAX: 416-756-7346 [email protected] www.dvnet.com Passport Certificate Server V.4.1.1 Security Target 30 April 2002 Common Criteria EAL 2 (augmented) Version 1.00 TABLE OF CONTENTS 1 Introduction ............................................................................................................................................ 1 1.1 Security Target Identification......................................................................................................... 1 1.2 Security Target Overview............................................................................................................... 1 1.3 Common Criteria Conformance .....................................................................................................1 2 TOE Description..................................................................................................................................... 2 2.1 Product Deployment....................................................................................................................... 2 2.2 Product Functions........................................................................................................................... 2 2.3 Product Description ........................................................................................................................ 3 2.3.1 Platform -
Certified Malware: Measuring Breaches of Trust in the Windows Code-Signing PKI
Certified Malware: Measuring Breaches of Trust in the Windows Code-Signing PKI Doowon Kim Bum Jun Kwon Tudor Dumitras, University of Maryland University of Maryland University of Maryland College Park, MD College Park, MD College Park, MD [email protected] [email protected] [email protected] ABSTRACT To establish trust in third-party software, we currently rely on Digitally signed malware can bypass system protection mechanisms the code-signing Public Key Infrastructure (PKI). This infrastruc- that install or launch only programs with valid signatures. It can ture includes Certification Authorities (CAs) that issue certificates also evade anti-virus programs, which often forego scanning signed to software publishers, vouching for their identity. Publishers use binaries. Known from advanced threats such as Stuxnet and Flame, these certificates to sign the software they release, and users rely this type of abuse has not been measured systematically in the on these signatures to decide which software packages to trust broader malware landscape. In particular, the methods, effective- (rather than maintaining a list of trusted packages). If adversaries ness window, and security implications of code-signing PKI abuse can compromise code signing certificates, this has severe impli- are not well understood. We propose a threat model that highlights cations for end-host security. Signed malware can bypass system three types of weaknesses in the code-signing PKI. We overcome protection mechanisms that install or launch only programs with challenges specific to code-signing measurements by introducing valid signatures, and it can evade anti-virus programs, which often techniques for prioritizing the collection of code-signing certificates neglect to scan signed binaries. -
Introduction to Cryptography
Mag. iur. Dr. techn. Michael Sonntag Introduction to Cryptography Institute of Networks and Security Johannes Kepler University Linz, Austria E-Mail: [email protected] Thanks to Rudolf Hörmanseder for some slides (esp. drawings!) Why cryptography? Security is a very important aspect, especially if money (or equivalents) are affected by transactions Not every information should be available to everyone Note: Data is sent in the Internet over numerous "open systems", where anyone can listen it! Security is needed! The technical aspect of security is cryptography Encrypting data against disclosure and modifications Signing data against modifications and repudiation Note: Cryptography does not solve all security problems! Example: Communication analysis (who talks to whom when) Other aspects of security are also needed » E.g.: Do you know what your employees actually do with data? Solutions: DRM, deactivation codes, anonymizers, … Michael Sonntag Introduction to Cryptography 2 Application areas Storing data in encrypted form Even access will not lead to disclosure (stolen laptops!) Example: File/-system encryption, password storage Transmitting data securely Enc. transmission prevents eavesdropping and tampering Example: TLS Identifying your partner Preventing man-in-the-middle attacks Example: TLS with uni-/bidirectional certificates Proof of identity & authority Avoiding impersonation Example: GPG E-Mail signatures, digital signatures (Austria: "Bürgerkarte“ – “citizen card”) Michael Sonntag Introduction to -
The Double Ratchet Algorithm
The Double Ratchet Algorithm Trevor Perrin (editor) Moxie Marlinspike Revision 1, 2016-11-20 Contents 1. Introduction 3 2. Overview 3 2.1. KDF chains . 3 2.2. Symmetric-key ratchet . 5 2.3. Diffie-Hellman ratchet . 6 2.4. Double Ratchet . 13 2.6. Out-of-order messages . 17 3. Double Ratchet 18 3.1. External functions . 18 3.2. State variables . 19 3.3. Initialization . 19 3.4. Encrypting messages . 20 3.5. Decrypting messages . 20 4. Double Ratchet with header encryption 22 4.1. Overview . 22 4.2. External functions . 26 4.3. State variables . 26 4.4. Initialization . 26 4.5. Encrypting messages . 27 4.6. Decrypting messages . 28 5. Implementation considerations 29 5.1. Integration with X3DH . 29 5.2. Recommended cryptographic algorithms . 30 6. Security considerations 31 6.1. Secure deletion . 31 6.2. Recovery from compromise . 31 6.3. Cryptanalysis and ratchet public keys . 31 1 6.4. Deletion of skipped message keys . 32 6.5. Deferring new ratchet key generation . 32 6.6. Truncating authentication tags . 32 6.7. Implementation fingerprinting . 32 7. IPR 33 8. Acknowledgements 33 9. References 33 2 1. Introduction The Double Ratchet algorithm is used by two parties to exchange encrypted messages based on a shared secret key. Typically the parties will use some key agreement protocol (such as X3DH [1]) to agree on the shared secret key. Following this, the parties will use the Double Ratchet to send and receive encrypted messages. The parties derive new keys for every Double Ratchet message so that earlier keys cannot be calculated from later ones. -
Security Analysis of the Signal Protocol Student: Bc
ASSIGNMENT OF MASTER’S THESIS Title: Security Analysis of the Signal Protocol Student: Bc. Jan Rubín Supervisor: Ing. Josef Kokeš Study Programme: Informatics Study Branch: Computer Security Department: Department of Computer Systems Validity: Until the end of summer semester 2018/19 Instructions 1) Research the current instant messaging protocols, describe their properties, with a particular focus on security. 2) Describe the Signal protocol in detail, its usage, structure, and functionality. 3) Select parts of the protocol with a potential for security vulnerabilities. 4) Analyze these parts, particularly the adherence of their code to their documentation. 5) Discuss your findings. Formulate recommendations for the users. References Will be provided by the supervisor. prof. Ing. Róbert Lórencz, CSc. doc. RNDr. Ing. Marcel Jiřina, Ph.D. Head of Department Dean Prague January 27, 2018 Czech Technical University in Prague Faculty of Information Technology Department of Computer Systems Master’s thesis Security Analysis of the Signal Protocol Bc. Jan Rub´ın Supervisor: Ing. Josef Kokeˇs 1st May 2018 Acknowledgements First and foremost, I would like to express my sincere gratitude to my thesis supervisor, Ing. Josef Kokeˇs,for his guidance, engagement, extensive know- ledge, and willingness to meet at our countless consultations. I would also like to thank my brother, Tom´aˇsRub´ın,for proofreading my thesis. I cannot express enough gratitude towards my parents, Lenka and Jaroslav Rub´ınovi, who supported me both morally and financially through my whole studies. Last but not least, this thesis would not be possible without Anna who re- lentlessly supported me when I needed it most. Declaration I hereby declare that the presented thesis is my own work and that I have cited all sources of information in accordance with the Guideline for adhering to ethical principles when elaborating an academic final thesis. -
SSL/TLS Interception Proxies and Transitive Trust Jeff Jarmoc Dell Secureworks Counter Threat Unit℠ Threat Intelligence
SSL/TLS Interception Proxies and Transitive Trust Jeff Jarmoc Dell SecureWorks Counter Threat Unit℠ Threat Intelligence Presented at Black Hat Europe – March 14, 2012. Introduction Secure Sockets Layer (SSL) [1] and its successor Transport Layer Security (TLS) [2] have become key components of the modern Internet. The privacy, integrity, and authenticity [3] [4] provided by these protocols are critical to allowing sensitive communications to occur. Without these systems, e- commerce, online banking, and business-to-business exchange of information would likely be far less frequent. Threat actors have also recognized the benefits of transport security, and they are increasingly turning to SSL to hide their activities. Advanced Persistent Threat (APT) attackers [5], botnets [6], and even commodity web attacks can leverage SSL encryption to evade detection. To counter these tactics, organizations are increasingly deploying security controls that intercept end- to-end encrypted channels. Web proxies, data loss prevention (DLP) systems, specialized threat detection solutions, and network intrusion prevention systems (NIPS) offer functionality to intercept, inspect, and filter encrypted traffic. Similar functionality is present in lawful intercept systems and solutions enabling the broad surveillance of encrypted communications by governments. Broadly classified as “SSL/TLS interception proxies,” these solutions act as a “man in the middle,” violating the end-to-end security promises of SSL. This type of interception comes at a cost. Intercepting SSL-encrypted connections sacrifices a degree of privacy and integrity for the benefit of content inspection, often at the risk of authenticity and endpoint validation. Implementers and designers of SSL interception proxies should consider these risks and understand how their systems operate in unusual circumstances. -
A Practical Evaluation of a High-Security Energy-Efficient
sensors Article A Practical Evaluation of a High-Security Energy-Efficient Gateway for IoT Fog Computing Applications Manuel Suárez-Albela * , Tiago M. Fernández-Caramés , Paula Fraga-Lamas and Luis Castedo Department Computer Engineering, Faculty of Computer Science, Universidade da Coruña, 15071 A Coruña, Spain; [email protected] (T.M.F.-C.); [email protected] (P.F.-L.); [email protected] (L.C.) * Correspondence: [email protected]; Tel.: +34-981-167-000 (ext. 6051) Received: 28 July 2017; Accepted: 19 August 2017; Published: 29 August 2017 Abstract: Fog computing extends cloud computing to the edge of a network enabling new Internet of Things (IoT) applications and services, which may involve critical data that require privacy and security. In an IoT fog computing system, three elements can be distinguished: IoT nodes that collect data, the cloud, and interconnected IoT gateways that exchange messages with the IoT nodes and with the cloud. This article focuses on securing IoT gateways, which are assumed to be constrained in terms of computational resources, but that are able to offload some processing from the cloud and to reduce the latency in the responses to the IoT nodes. However, it is usually taken for granted that IoT gateways have direct access to the electrical grid, which is not always the case: in mission-critical applications like natural disaster relief or environmental monitoring, it is common to deploy IoT nodes and gateways in large areas where electricity comes from solar or wind energy that charge the batteries that power every device. In this article, how to secure IoT gateway communications while minimizing power consumption is analyzed. -
Is Bob Sending Mixed Signals?
Is Bob Sending Mixed Signals? Michael Schliep Ian Kariniemi Nicholas Hopper University of Minnesota University of Minnesota University of Minnesota [email protected] [email protected] [email protected] ABSTRACT Demand for end-to-end secure messaging has been growing rapidly and companies have responded by releasing applications that imple- ment end-to-end secure messaging protocols. Signal and protocols based on Signal dominate the secure messaging applications. In this work we analyze conversational security properties provided by the Signal Android application against a variety of real world ad- versaries. We identify vulnerabilities that allow the Signal server to learn the contents of attachments, undetectably re-order and drop messages, and add and drop participants from group conversations. We then perform proof-of-concept attacks against the application to demonstrate the practicality of these vulnerabilities, and suggest mitigations that can detect our attacks. The main conclusion of our work is that we need to consider more than confidentiality and integrity of messages when designing future protocols. We also stress that protocols must protect against compromised servers and at a minimum implement a trust but verify model. 1 INTRODUCTION (a) Alice’s view of the conversa-(b) Bob’s view of the conversa- Recently many software developers and companies have been inte- tion. tion. grating end-to-end encrypted messaging protocols into their chat applications. Some applications implement a proprietary protocol, Figure 1: Speaker inconsistency in a conversation. such as Apple iMessage [1]; others, such as Cryptocat [7], imple- ment XMPP OMEMO [17]; but most implement the Signal protocol or a protocol based on Signal, including Open Whisper Systems’ caching. -
Measuring Breaches of Trust in the Windows Code-Signing PKI
Session F5: Understanding Security Fails CCS’17, October 30-November 3, 2017, Dallas, TX, USA Certified Malware: Measuring Breaches of Trust in the Windows Code-Signing PKI Doowon Kim Bum Jun Kwon Tudor Dumitras, University of Maryland University of Maryland University of Maryland College Park, MD College Park, MD College Park, MD [email protected] [email protected] [email protected] ABSTRACT To establish trust in third-party software, we currently rely on Digitally signed malware can bypass system protection mechanisms the code-signing Public Key Infrastructure (PKI). This infrastruc- that install or launch only programs with valid signatures. It can ture includes Certification Authorities (CAs) that issue certificates also evade anti-virus programs, which often forego scanning signed to software publishers, vouching for their identity. Publishers use binaries. Known from advanced threats such as Stuxnet and Flame, these certificates to sign the software they release, and users rely this type of abuse has not been measured systematically in the on these signatures to decide which software packages to trust broader malware landscape. In particular, the methods, effective- (rather than maintaining a list of trusted packages). If adversaries ness window, and security implications of code-signing PKI abuse can compromise code signing certificates, this has severe impli- are not well understood. We propose a threat model that highlights cations for end-host security. Signed malware can bypass system three types of weaknesses in the code-signing PKI. We overcome protection mechanisms that install or launch only programs with challenges specific to code-signing measurements by introducing valid signatures, and it can evade anti-virus programs, which often techniques for prioritizing the collection of code-signing certificates neglect to scan signed binaries. -
Security Policies for the Federal Public Key Infrastructure
Security Policies for the Federal Public Key Infrastructure Noel A. Nazario Security Technology Group National Institute of Standards and Technology Abstract This document discusses provisions for the handling of security policies in the proposed Federal Public Key Infrastructure (PKI). Federal PKI policies deal with the generation, deactivation, and dissemination of public key certificates, the integrity of the infrastructure, maintenance of records, identification of certificate holders, and the establishment of trust relationships between Certification Authorities (CAs). The verification of a digital signature is not sufficient indication of the trustworthiness of an electronic message or data file. The verifier needs to factor the trustworthiness of the CAs involved in the certification of the sender. To accomplish this, the verifier needs to examine the certificate policy for those CAs. The Federal PKI Technical Security Policy establishes guidelines for the operation of Federal CAs and the identification of the parties requesting certification. It also defines Policy Approving Authorities (PAA) responsible for assessing the policies and operational practices of all Federal CAs within a domain and assigning them corresponding Federal Assurance Levels. These assurance levels may be used in lieu of a certificate policy when making an on-line determination of the trustworthiness of a certificate. Key words Certificate policy, Federal Assurance Levels, PAA, PKI, Policy Approving Authority, public key infrastructure, security policy. SECURITY POLICIES FOR THE FEDERAL PUBLIC KEY INFRASTRUCTURE Noel A. Nazario NIST North, Room 426 820 West Diamond Avenue Gaithersburg, MD 20899 [email protected] Introduction and Background This paper discusses provisions for the handling of security policies in the proposed Federal Public Key Infrastructure (PKI).