NETWORK SECURITY
1012021:- Chiranjeev Shah
1012025:- Dhaval Bhatia
1012027:- Dipesh Ingawle
Introduction to Cryptography
 Cryptography is a word from Greek where crpyto 
means "hidden, secret"; and graphy means 
"...
Applications of Cryptography
    Applications of cryptography include ATM 
cards, computer passwords, and electronic 
comm...
Cryptography components
ALICE , BOB and EVE
 In cryptography, it is customary to use three
Characters in an information exchange.
 ALICE:- who N...
Categories of cryptography
Symmetric-key cryptography
In symmetric-key cryptography, theIn symmetric-key cryptography, the
same key is used by the se...
Asymmetric-key cryptography
Keys used in cryptography
Comparison between two categories of cryptography
SECURITY SERVICESSECURITY SERVICES
Network security can provide five services. Four of theseNetwork security can provide f...
Message Confidentiality
The concept of how to achieve message confidentiality or privacyThe concept of how to achieve mess...
Message confidentiality using symmetric keys in two directions
Message confidentiality using asymmetric keys
MESSAGE INTEGRITYMESSAGE INTEGRITY
 Encryption and decryption provide secrecy, or confidentiality,Encryption and decrypti...
Message and message digest
The message digest needs to be kept secret.The message digest needs to be kept secret.
MESSAGE AUTHENTICATIONMESSAGE AUTHENTICATION
 A hash function per se cannot provide authentication. TheA hash function pe...
DIGITAL SIGNATUREDIGITAL SIGNATURE
 When Alice sends a message to Bob, Bob needs to check theWhen Alice sends a message t...
ENTITYAUTHENTICATIONENTITYAUTHENTICATION
 Entity authentication is a technique designedEntity authentication is a techniq...
KEY MANAGEMENTKEY MANAGEMENT
 We never discussed how secret keys inWe never discussed how secret keys in
symmetric-key cr...
Thank You
K. J. SOMAIYA COLLEGE OF ENGINEERING
Electronics Engineering
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Network securities cn

  1. 1. NETWORK SECURITY 1012021:- Chiranjeev Shah 1012025:- Dhaval Bhatia 1012027:- Dipesh Ingawle
  2. 2. Introduction to Cryptography  Cryptography is a word from Greek where crpyto  means "hidden, secret"; and graphy means  "writing" or "study“ . It is the practice and study of  techniques for secure communication in the  presence of third parties .  More generally, it is about constructing and  analyzing protocols that overcome the influence of  adversaries and which are related to various  aspects in information security such as data  confidentiality, data integrity and authentication.  
  3. 3. Applications of Cryptography     Applications of cryptography include ATM  cards, computer passwords, and electronic  commerce. German Lorenz cipher  machine, used in World War II to encrypt  very-high-level  general staff messages
  4. 4. Cryptography components
  5. 5. ALICE , BOB and EVE  In cryptography, it is customary to use three Characters in an information exchange.  ALICE:- who Needs to send the DATA.  BOB:- recipient of the DATA  EVE:- person who somehow disturbs the communication between Alice and Bob
  6. 6. Categories of cryptography
  7. 7. Symmetric-key cryptography In symmetric-key cryptography, theIn symmetric-key cryptography, the same key is used by the sendersame key is used by the sender (for encryption)(for encryption) and the receiver (for decryption).and the receiver (for decryption). The key is shared.The key is shared.
  8. 8. Asymmetric-key cryptography
  9. 9. Keys used in cryptography
  10. 10. Comparison between two categories of cryptography
  11. 11. SECURITY SERVICESSECURITY SERVICES Network security can provide five services. Four of theseNetwork security can provide five services. Four of these services are related to the message exchanged using theservices are related to the message exchanged using the network. The fifth service provides entity authenticationnetwork. The fifth service provides entity authentication or identification.or identification. Message ConfidentialityMessage Confidentiality Message IntegrityMessage Integrity Message AuthenticationMessage Authentication Message NonrepudiationMessage Nonrepudiation Entity AuthenticationEntity Authentication
  12. 12. Message Confidentiality The concept of how to achieve message confidentiality or privacyThe concept of how to achieve message confidentiality or privacy has not changed for thousands of years. The message must behas not changed for thousands of years. The message must be encrypted at the sender site and decrypted at the receiver site.encrypted at the sender site and decrypted at the receiver site. This can be done using either symmetric-key cryptography orThis can be done using either symmetric-key cryptography or asymmetric-key cryptography.asymmetric-key cryptography.
  13. 13. Message confidentiality using symmetric keys in two directions
  14. 14. Message confidentiality using asymmetric keys
  15. 15. MESSAGE INTEGRITYMESSAGE INTEGRITY  Encryption and decryption provide secrecy, or confidentiality,Encryption and decryption provide secrecy, or confidentiality, but not integrity. However, on occasion we may not even needbut not integrity. However, on occasion we may not even need secrecy, but instead must have integrity.secrecy, but instead must have integrity. To preserve the integrity of a document,To preserve the integrity of a document, both the document and the fingerprint areboth the document and the fingerprint are needed.needed.
  16. 16. Message and message digest The message digest needs to be kept secret.The message digest needs to be kept secret.
  17. 17. MESSAGE AUTHENTICATIONMESSAGE AUTHENTICATION  A hash function per se cannot provide authentication. TheA hash function per se cannot provide authentication. The digest created by a hash function can detect any modificationdigest created by a hash function can detect any modification in the message, but not authentication.in the message, but not authentication.
  18. 18. DIGITAL SIGNATUREDIGITAL SIGNATURE  When Alice sends a message to Bob, Bob needs to check theWhen Alice sends a message to Bob, Bob needs to check the authenticity of the sender; he needs to be sure that theauthenticity of the sender; he needs to be sure that the message comes from Alice and not Eve. Bob can ask Alice tomessage comes from Alice and not Eve. Bob can ask Alice to sign the message electronically. In other words, an electronicsign the message electronically. In other words, an electronic signature can prove the authenticity of Alice as the sender ofsignature can prove the authenticity of Alice as the sender of the message. We refer to this type of signature as a digitalthe message. We refer to this type of signature as a digital signature.signature. A digital signature needs a public-key system.A digital signature needs a public-key system.
  19. 19. ENTITYAUTHENTICATIONENTITYAUTHENTICATION  Entity authentication is a technique designedEntity authentication is a technique designed to let one party prove the identity of anotherto let one party prove the identity of another party. An entity can be a person, a process, aparty. An entity can be a person, a process, a client, or a server. The entity whose identityclient, or a server. The entity whose identity needs to be proved is called the claimant; theneeds to be proved is called the claimant; the party that tries to prove the identity of theparty that tries to prove the identity of the claimant is called the verifier.claimant is called the verifier.  In challenge-response authentication, the claimant proves that she knows a secret without revealing it.
  20. 20. KEY MANAGEMENTKEY MANAGEMENT  We never discussed how secret keys inWe never discussed how secret keys in symmetric-key cryptography and how publicsymmetric-key cryptography and how public keys in asymmetric-key cryptography arekeys in asymmetric-key cryptography are distributed and maintained. In this section,distributed and maintained. In this section, we touch on these two issues. We firstwe touch on these two issues. We first discuss the distribution of symmetric keys;discuss the distribution of symmetric keys; we then discuss the distribution ofwe then discuss the distribution of asymmetric keys.asymmetric keys. A session symmetric key between two parties isA session symmetric key between two parties is used only once.used only once.
  21. 21. Thank You K. J. SOMAIYA COLLEGE OF ENGINEERING Electronics Engineering

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