Subject Name: NETWORK SECURITY Subject Code: 10 EC 832 Prepared By: SHAIK KAREEMULLA & BENJAMIN I Department: ELECTRONICS AND COMMUNICATION ENGINEERING Engineered for Tomorrow Prepared by : Kareemulla & Benjamin Department : Electronics and Communication Engg 3/16/2018 Date : 16. 02. 2015
UNIT I 3/16/2018
TOPICS TO BE COVERED: Services, Mechanism Attacks, The OSI security architecture, A model for network security. (6 Hrs) 3/16/2018
Computer Security The protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability and confidentiality of information system resources (includes hardware, software, firmware, information/data, and telecommunications) 3/16/2018
Key Security Concepts 3/16/2018
Three Key Objectives • Confidentiality – Data confidentiality – Privacy • Integrity – Data integrity – System integrity • Availability • Additional concepts – Authenticity – Accountability
Levels of Impact • 3 levels of impact from a security breach – Low – Moderate – High 3/16/2018
Examples of Security Requirements • confidentiality – student grades • integrity – patient information • availability – authentication service 3/16/2018
Computer Security Challenges not simple 2. must consider potential attacks 3. procedures used counter-intuitive 4. involve algorithms and secret info 5. must decide where to deploy mechanisms 6. battle of wits between attacker / admin 7. not perceived on benefit until fails 8. requires regular monitoring 9. too often an after-thought 10. regarded as impediment to using system 1. 3/16/2018
OSI Security Architecture • ITU-T X. 800 “Security Architecture for OSI” • defines a systematic way of defining and providing security requirements • for us it provides a useful, if abstract, overview of concepts we will study
Aspects of Security • 3 aspects of information security: – security attack – security mechanism: detect, prevent, recover – security service • terms – threat – a potential for violation of security – attack – an assault on system security, a deliberate attempt to evade security services
Passive Attacks (1) Release of Message Contents 3/16/2018
Passive Attacks (2) Traffic Analysis 3/16/2018
• Passive attacks do not affect system resources – Eavesdropping, monitoring • Two types of passive attacks – Release of message contents – Traffic analysis • Passive attacks are very difficult to detect – Message transmission apparently normal • No alteration of the data – Emphasis on prevention rather than detection • By means of encryption
Active Attacks (1) Masquerade
Active Attacks (2) Replay
Active Attacks (3) Modification of Messages 3/16/2018
Active Attacks (4) Denial of Service
• Active attacks try to alter system resources or affect their operation – Modification of data, or creation of false data • Four categories – – Masquerade Replay Modification of messages Denial of service: preventing normal use • A specific target or entire network • Difficult to prevent – The goal is to detect and recover
Security Service – enhance security of data processing systems and information transfers of an organization – intended to counter security attacks – using one or more security mechanisms – often replicates functions normally associated with physical documents • which, for example, have signatures, dates; need protection from disclosure, tampering, or destruction; be notarized or witnessed; be recorded or licensed
Security Services • X. 800: “a service provided by a protocol layer of communicating open systems, which ensures adequate security of the systems or of data transfers” • RFC 2828: “a processing or communication service provided by a system to give a specific kind of protection to system resources” 3/16/2018
Security Services (X. 800) • Authentication - assurance that communicating entity is the one claimed – have both peer-entity & data origin authentication • Access Control - prevention of the unauthorized use of a resource • Data Confidentiality –protection of data from unauthorized disclosure • Data Integrity - assurance that data received is as sent by an authorized entity • Non-Repudiation - protection against denial by one of the parties in a communication • Availability – resource accessible/usable
Security Mechanism • feature designed to detect, prevent, or recover from a security attack • no single mechanism that will support all services required • however one particular element underlies many of the security mechanisms in use: – cryptographic techniques • hence our focus on this topic
Security Mechanisms • specific security mechanisms: – encipherment, digital signatures, access controls, data integrity, authentication exchange, traffic padding, routing control, notarization • pervasive security mechanisms: – trusted functionality, security labels, event detection, security audit trails, security recovery
3/16/2018
Model for Network Security
• Model for Network Security using this model requires us to: 1. design a suitable algorithm for the security transformation 2. generate the secret information (keys) used by the algorithm 3. develop methods to distribute and share the secret information 4. specify a protocol enabling the principals to use the transformation and secret information for a security service
Model for Network Access Security
Model for Network Access Security • using this model requires us to: 1. select appropriate gatekeeper functions to identify users 2. implement security controls to ensure only authorised users access designated information or resources 3/16/2018
Standards • NIST: National Institute of Standards and Technology – FIPS: Federal Information Processing Standards – SP: Special Publications • ISOC: Internet Society – Home for IETF (Internet Engineering Task Force) and IAB (Internet Architecture Board) – RFCs: Requests for Comments
Summary • topic roadmap & standards organizations • security concepts: – confidentiality, integrity, availability • security architecture • security attacks, services, mechanisms • models for network (access) security
Exercise 1. Write a note on security Services. 2. Explain Security Mechanisms. 3. What are the types of security attacks? Explain in details. 4. What are things on which OSI security model focuses? 5. With a block diagram explain network security model in detail.
UNIT -2 SYMMETRIC CIPHER MODEL 3/16/2018
Contents • INTRODUCTION • CRYPTOGRAPHY • NEED FOR SECURITY • • SYMMETRIC CIPHER MODEL OF CONVENTIONAL CRYPTOSYSTEM THE DATA ENCRYPTION STANDARD DES ENCRYPTION ALGORITHM (DES 3) TRIPLE DATA ENCRYPTION STANDARD APPLICATIONS CONCLUSION (7 Hrs) 3/16/2018
INTRODUCTION ü Power analysis attacks have attracted significant attention within the cryptographic community. So far, they have been successfully applied to different kinds of (unprotected) symmetric and public-key encryption schemes. ü In Boolean Masking has been successfully applied to smart card implementations of the DES and the AES. ü The protected algorithms usually have much higher memory requirements than the unmasked ones. For this reason, it is often assumed that masking is not a practical solution for the protection of hardware implementations.
CRYPTOGRAPHY v Cryptography is the study of mathematical techniques related to aspects of information security such as confidentiality, data integrity, entity authentication, and origin authentication. v There are two kinds of cryptosystems: 1. symmetric 2. asymmetric v Symmetric cryptosystems use the same key (the secret key) to encrypt and decrypt a message. v Asymmetric cryptosystems use one key (the public key) to encrypt a message and a different key (the private key) to decrypt it. Asymmetric cryptosystems are also called public key cryptosystems.
Need for security • Steps involved in secured communication: 1. Design an algorithm for performing the security related transformation such that the opponent cannot defeat its purpose. 2. Generate the secret information to be used with the algorithm. 3. Specify the protocol to be used by the two principles that make use of the security algorithm. Threats in communication • Information access threat: Modification of the data without the knowledge of sender and then transmit the data. • Service threat: Exploit this flaws in the services available in computer to inhibit the use by legitimate users.
SYMMETRIC CIPHER MODEL Secret key shared by sender and recipient Encryption Process Plaintext input Transmitted Cipher text Encryption Algorithm e. g. : TDES Decryption Process Decryption Algorithm Plaintext output (reverse of Encryption Algorithm) Simplified Model of Conventional Encryption 3/16/2018
MODEL OF CONVENTIONAL CRYPTOSYSTEM
THE DATA ENCRYPTION STANDARD • DES is the most widely used symmetric algorithm in the world, because the key length is too short. Since DES was first announced, controversy has raged about whether 56 bits is long enough to guarantee security. • Just applying DES twice, double DES, is ineffective. Using two 56 bit keys gives 112 total key bits, so a brute force attack needs 2111 encryptions. However, brute force is not the best attack. • Advanced Encryption Standard (AES) will be at least as strong as Triple DES and probably much faster.
Limitations of DES • Generating the per-round keys that the key is subjected to an a initial permutation to generate two 28 – bit quantities C 0 and D 0. The sixteen suspect keys are ones for which , C 0 and D 0 are one of the four values : all ones , all zeroes , alternating ones and zeroes , alternating zeroes and ones. Since there are four possible values for each half , there are sixteen possibilities in all. • The four weak keys are the ones for which each of , C 0 and D 0 are all ones or all zeroes. Weak keys are their own inverses. The remaining twelve keys are the semi- weak keys. Each is the inverse of one of the others. 3/16/2018
Applications of DES The DES core can be utilized for a variety of encryption applications including: • Secure File/Data transfer • Electronic Funds Transfer • Encrypted Storage Data • Secure communications Features of DES • Encryption/Decryption performed in 16 cycles (ECB mode) • 56 bits of security • For use in FPGA designs • Verilog IP Core
(DES 3) Triple Data Encryption Standard ü The DES 3 core is a block cipher, working on 64 bits of data at a time. It is built upon the Data Encryption Standard (DES) core. Key length is 64 bits of which only 56 bits are used. ü The DES 3 Low Gate version is implemented to minimize gate count or FPGA resources. The design does not use any memories such as SRAM. ü The DES 3 Pipelined version is implemented to maximize performance by pipelining the DES algorithm through three DESPL instantiations.
TDES Encryption TDES Decryption
DES ENCRYPTION ALGORITHM 3/16/2018
INPUT 64 BIT BLOCK DIAG FOR INPUT DATA KEY 48 BITS INITIAL PERMUTATION LEFT 32 BITS RIGHT 32 BITS 32 bits EXPANSION PERMUTATION 48 bits S-BOX XOR 32 bits Li 3/16/2018 32 bits Ri 32 bits PERMUTATION BOX
56 BITS INPUT 64 BIT 8 BITS FOR PARITY PERMUTATION CHOICE(PC 1) BLOCK DIAGRAM FOR KEY GENERATION 56 BITS 48 bits 48 BIT KEY EXPANSION PERMUTATION 3/16/2018 48 bits XOR PERMUTATION CHOICE(PC 2) S-BOX
Single Round of DES 3/16/2018
Initial permutation (IP) Table- Initial permutation IP 58 42 34 26 18 10 2 60 52 44 36 28 20 12 4 62 54 46 38 30 22 14 6 64 56 48 40 32 24 16 8 57 49 41 33 25 17 9 1 59 51 43 35 27 19 11 3 61 53 45 37 29 21 13 5 63 3/16/2018 50 55 47 39 31 23 15 7
Expansion permutation (E) Table- Expansion permutation E 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 1
Substitution boxes (S-boxes)
TDES Algorithm 3/16/2018
Applications of DES 3 The DES 3 core can be utilized for a variety of encryption applications including: : • Secure File/Data transfer • Electronic Funds Transfer • Encrypted Storage Data • Secure communications Features of DES 3 • Encryption/Decryption performed in 48 cycles(ECB mode) • Up to 168 bits of security • For use in FPGA or ASIC designs • Verilog IP Core 3/16/2018
Origins AES • clear a replacement for DES was needed – have theoretical attacks that can break it – have demonstrated exhaustive key search attacks • can use Triple-DES – but slow with small blocks • US NIST issued call for ciphers in 1997 • 15 candidates accepted in Jun 98 • 5 were shortlisted in Aug-99 • Rijndael was selected as the AES in Oct-2000 • issued as FIPS PUB 197 standard in Nov-2001
AES Requirements • • private key symmetric block cipher 128 -bit data, 128/192/256 -bit keys stronger & faster than Triple-DES active life of 20 -30 years (+ archival use) provide full specification & design details both C & Java implementations NIST have released all submissions & unclassified analyses
AES Evaluation Criteria • initial criteria: – security – effort to practically cryptanalyse – cost – computational – algorithm & implementation characteristics • final criteria – general security – software & hardware implementation ease – implementation attacks – flexibility (in en/decrypt, keying, other factors) 3/16/2018
AES Shortlist • after testing and evaluation, shortlist in Aug-99: – – – MARS (IBM) - complex, fast, high security margin RC 6 (USA) - v. simple, v. fast, low security margin Rijndael (Belgium) - clean, fast, good security margin Serpent (Euro) - slow, clean, v. high security margin Twofish (USA) - complex, v. fast, high security margin • then subject to further analysis & comment • saw contrast between algorithms with – few complex rounds verses many simple rounds – which refined existing ciphers verses new proposals 3/16/2018
The AES Cipher - Rijndael • designed by Rijmen-Daemen in Belgium • has 128/192/256 bit keys, 128 bit data • an iterative rather than feistel cipher – treats data in 4 groups of 4 bytes – operates an entire block in every round • designed to be: – resistant against known attacks – speed and code compactness on many CPUs – design simplicity
Rijndael • processes data as 4 groups of 4 bytes (state) • has 9/11/13 rounds in which state undergoes: – – byte substitution (1 S-box used on every byte) shift rows (permute bytes between groups/columns) mix columns (subs using matrix multipy of groups) add round key (XOR state with key material) • initial XOR key material & incomplete last round • all operations can be combined into XOR and table lookups - hence very fast & efficient
AES
Byte Substitution • a simple substitution of each byte • uses one table of 16 x 16 bytes containing a permutation of all 256 8 -bit values • each byte of state is replaced by byte in row (left 4 -bits) & column (right 4 -bits) – eg. byte {95} is replaced by row 9 col 5 byte – which is the value {2 A} • S-box is constructed using a defined transformation of the values in GF(28) • designed to be resistant to all known attacks 3/16/2018
Shift Rows • a circular byte shift in each – 1 st row is unchanged – 2 nd row does 1 byte circular shift to left – 3 rd row does 2 byte circular shift to left – 4 th row does 3 byte circular shift to left • decrypt does shifts to right • since state is processed by columns, this step permutes bytes between the columns
Mix Columns • each column is processed separately • each byte is replaced by a value dependent on all 4 bytes in the column • effectively a matrix multiplication in GF(28) using prime poly m(x) =x 8+x 4+x 3+x+1
Add Round Key • XOR state with 128 -bits of the round key • again processed by column (though effectively a series of byte operations) • inverse for decryption is identical since XOR is own inverse, just with correct round key • designed to be as simple as possible
AES Round 3/16/2018
AES Key Expansion • takes 128 -bit (16 -byte) key and expands into array of 44/52/60 32 -bit words • start by copying key into first 4 words • then loop creating words that depend on values in previous & 4 places back – in 3 of 4 cases just XOR these together – every 4 th has S-box + rotate + XOR constant of previous before XOR together • designed to resist known attacks
AES Decryption • AES decryption is not identical to encryption since steps done in reverse • but can define an equivalent inverse cipher with steps as for encryption – but using inverses of each step – with a different key schedule • works since result is unchanged when – swap byte substitution & shift rows – swap mix columns & add (tweaked) round key
Implementation Aspects • can efficiently implement on 8 -bit CPU – byte substitution works on bytes using a table of 256 entries – shift rows is simple byte shifting – add round key works on byte XORs – mix columns requires matrix multiply in GF(28) which works on byte values, can be simplified to use a table lookup
Implementation Aspects • can efficiently implement on 32 -bit CPU – redefine steps to use 32 -bit words – can precompute 4 tables of 256 -words – then each column in each round can be computed using 4 table lookups + 4 XORs – at a cost of 16 Kb to store tables • designers believe this very efficient implementation was a key factor in its selection as the AES cipher 3/16/2018
Summary • have considered: – the AES selection process – the details of Rijndael – the AES cipher – looked at the steps in each round – the key expansion – implementation aspects
Exercise 1. Explain CASER cipher and disadvantages of it. 2. Explain PLAYER FAIR method for the key board CRYPTOGRAPHY give cipher text for plain text electronics and communication. 3. What is Hill cipher algorithm? Explain briefly. 4. Differentiate between block cipher and stream cipher. 5. Differentiate between monoalphabetic and pdyalphabetic. 6. What is the principle behind DES algorithm? Explain encryption and decryption of DES. 7. What are the models of operation in block cipher? 8. Write a note on AES cipher.
UNIT 7 Malicious software programs 3/16/2018
Contents Viruses and related Threats, Virus Countermeasures (7 Hrs) 3/16/2018
Viruses and Other Malicious Content Ø computer viruses have got a lot of publicity Ø one of a family of malicious software Ø effects usually obvious Ø have figured in news reports, fiction, movies (often exaggerated) Ø getting more attention than deserve Ø are a concern though
Malicious Software
Backdoor or Trapdoor • secret entry point into a program • allows those who know access bypassing usual security procedures • have been commonly used by developers • a threat when left in production programs allowing exploited by attackers • very hard to block in O/S • requires good s/w development & update
Logic Bomb • one of oldest types of malicious software • code embedded in legitimate program • activated when specified conditions met – eg presence/absence of some file – particular date/time – particular user • when triggered typically damage system – modify/delete files/disks, halt machine, etc 3/16/2018
Trojan Horse • program with hidden side-effects • which is usually superficially attractive – eg game, s/w upgrade etc • when run performs some additional tasks – allows attacker to indirectly gain access they do not have directly • often used to propagate a virus/worm or install a backdoor • or simply to destroy data
Mobile Code Ø program/script/macro that runs unchanged l on heterogeneous collection of platforms l on large homogeneous collection (Windows) Ø transmitted from remote system to local system & then executed on local system Ø often to inject virus, worm, or Trojan horse Ø or to perform own exploits l unauthorized data access, root compromise
Multiple-Threat Malware Ø malware may operate in multiple ways Ø multipartite virus infects in multiple ways l eg. multiple file types Ø blended attack uses multiple methods of infection or transmission l to maximize speed of contagion and severity l may include multiple types of malware l eg. Nimda has worm, virus, mobile code l can also use IM & P 2 P
Viruses Ø piece of software that infects programs l modifying them to include a copy of the virus l so it executes secretly when host program is run Ø specific to operating system and hardware l taking advantage of their details and weaknesses Ø a typical virus goes through phases of: l dormant l propagation l triggering l execution 3/16/2018
Virus Structure Ø components: l infection mechanism - enables replication l trigger - event that makes payload activate l payload - what it does, malicious or benign Ø prepended / postpended / embedded Ø when infected program invoked, executes virus code then original program code Ø can block initial infection (difficult) Ø or propogation (with access controls)
Virus Structure
Compression Virus
Virus Classification Ø boot sector Ø file infector Ø macro virus Ø encrypted virus Ø stealth virus Ø polymorphic virus Ø metamorphic virus 3/16/2018
Macro Virus Ø became very common in mid-1990 s since l platform independent l infect documents l easily spread Ø exploit macro capability of office apps l executable program embedded in office doc l often a form of Basic Ø more recent releases include protection Ø recognized by many anti-virus programs
E-Mail Viruses Ø more recent development Ø e. g. Melissa l exploits MS Word macro in attached doc l if attachment opened, macro activates l sends email to all on users address list l and does local damage Ø then saw versions triggered reading email Ø hence much faster propagation
Virus Countermeasures • prevention - ideal solution but difficult • realistically need: – detection – identification – removal • if detect but can’t identify or remove, must discard and replace infected program
Anti-Virus Evolution Ø virus & antivirus tech have both evolved Ø early viruses simple code, easily removed Ø as become more complex, so must the countermeasures Ø generations l first - signature scanners l second - heuristics l third - identify actions l fourth - combination packages 3/16/2018
Exercise 1. Give the mechanisms of spreading nimda. 2. Explain the operation of compression virus with example. 3. Write a note on virus counter measures. 4. Give the taxonomy of malicious program. 5. List the software threats and explain in detail. 6. Write a note on email virus. 7. Discuss about digital immune system. 3/16/2018
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