IS Unit 8_IP Security and Email Security


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IS Unit 8_IP Security and Email Security

  1. 1. Chapter 8:Chapter 8:Chapter 8:Chapter 8:----IP Security EIP Security EIP Security EIP Security E----Mail Security:Mail Security:Mail Security:Mail Security:Sarthak Patel (
  2. 2. OutlineIP Security OverviewArchitectureAuthentication HeaderEncapsulation2Security PayloadCombining Security AssociationKey ManagementPretty Good PrivacyS/MimeAndTypesSarthak Patel (
  3. 3. TCP/IP Example3 Sarthak Patel (
  4. 4. IPv4 Header4 Sarthak Patel (
  5. 5. IPv6 Header5 Sarthak Patel (
  6. 6. IP Security OverviewIPSec is not a single protocol.Instead, IPSec provides a set of security algorithms plus a generalframework that allows a pair of communicating entities to usewhichever algorithms to provide security appropriate for thecommunication.• Applications of IPSec6• Applications of IPSec– Secure branch office connectivity over the Internet– Secure remote access over the Internet– Establsihing extranet and intranet connectivity with partners– Enhancing electronic commerce securitySarthak Patel (
  7. 7. IP Security Scenario7 Sarthak Patel (
  8. 8. IP Security OverviewBenefits of IPSecWhen IPSec is implemented in a firewall or router, it provides strongsecurity.IPSec in a firewall is resistant to bypass if all traffic from the outside must useIP, and the firewall is the only means of entrance from the Internet into theorganization.8IPSec is below the transport layer (TCP, UDP) and so is transparent toapplications. There is no need to change software on a user or server systemwhen IPSec is implemented in the firewall or router. Even if IPSec isimplemented in end systems, upper-layer software, including applications, isnot affected.IPSec can be transparent to end users. There is no need to train users onsecurity mechanisms, issue keying material on a per-user basis, or revokekeying material when users leave the organization.Sarthak Patel (
  9. 9. IP Security ArchitectureIPSec documents: NEW updates in 2005!The IPSec specification consists of numerous documents.Themost important of these, issued in November of 1998, are RFCs2401, 2402, 2406, and 2408:RFC 2401:An overview of a security architectureRFC 2402: Description of a packet authentication extension to9RFC 2402: Description of a packet authentication extension toIPv4 and IPv6RFC 2406: Description of a packet encryption extension toIPv4 and IPv6RFC 2408: Specification of key management capabilitiesSarthak Patel (
  10. 10. IP Security ArchitectureArchitecture: Covers the general concepts, security requirements, definitions, andmechanisms defining IPSec technology.Encapsulating Security Payload (ESP): Covers the packet format and general issuesrelated to the use of the ESP for packet encryption and, optionally, authentication.Authentication Header (AH): Covers the packet format and general issues relatedto the use ofAH for packet authentication.Encryption Algorithm: A set of documents that describe how various encryption10Encryption Algorithm: A set of documents that describe how various encryptionalgorithms are used for ESP.Authentication Algorithm: A set of documents that describe how variousauthentication algorithms are used forAH and for the authentication option of ESP.Key Management: Documents that describe key management schemes.Domain of Interpretation (DOI): Contains values needed for the other documentsto relate to each other. These include identifiers for approved encryption andauthentication algorithms, as well as operational parameters such as key lifetime.Sarthak Patel (
  11. 11. IPSec Document Overview11 Sarthak Patel (
  12. 12. IPSec ServicesAccess ControlConnectionless integrityData origin authenticationRejection of replayed packetsConfidentiality (encryption)12Confidentiality (encryption)Limited traffic flow confidentiallitySarthak Patel (
  13. 13. Security Associations (SA)A one way relationship between a sender and a receiver.Identified by three parameters:Security Parameters Index (SPI)IP Destination addressSecurity Protocol Identifier13Security Protocol IdentifierSarthak Patel (
  14. 14. SA ParametersSA ParametersSA ParametersSA ParametersSequence Number CounterSequence Counter OverflowAnti-ReplayWindowAH InformationESP Information14ESP InformationLifetime ofThis Security AssociationIPSec Protocol Mode:Tunnel, transportPath MTU (MaxTrans. Unit)Sarthak Patel (
  15. 15. Transport and Tunnel ModesTransport and Tunnel ModesTransport and Tunnel ModesTransport and Tunnel ModesTransport ModeTransport mode provides protection primarily for upper-layerprotocols.That is, transport mode protection extends to thepayload of an IP packet.Tunnel Mode15Tunnel ModeTunnel mode provides protection to the entire IP packet.Sarthak Patel (
  16. 16. Transport Mode SA Tunnel Mode SAAH Authenticates IP payloadand selected portions of IPheader and IPv6 extensionheadersAuthenticates entire innerIP packet plus selectedportions of outer IP header16ESP Encrypts IP payload and anyIPv6 extesion headerEncrypts inner IP packetESP withauthenticationEncrypts IP payload and anyIPv6 extesion header.Authenticates IP payloadbut no IP headerEncrypts inner IP packet.Authenticates inner IPpacket.Sarthak Patel (
  17. 17. Before applying AH17 Sarthak Patel (
  18. 18. Transport Mode(AH Authentication)18 Sarthak Patel (
  19. 19. Tunnel Mode(AH Authentication)19 Sarthak Patel (
  20. 20. Authentication HeaderProvides support for data integrity and authentication (MACcode) of IP packets.Guards against replay attacks.20 Sarthak Patel (
  21. 21. Encapsulating Security PayloadESP provides confidentiality services21 Sarthak Patel (
  22. 22. Encryption and Authentication AlgorithmsEncryption:Three-key triple DESRC5IDEAThree-key triple IDEACAST22CASTBlowfishAuthentication:HMAC-MD5-96HMAC-SHA-1-96Sarthak Patel (
  23. 23. ESP Encryption and Authentication23 Sarthak Patel (
  24. 24. ESP Encryption and Authentication24 Sarthak Patel (
  25. 25. Combinations of Security Associations25In Case 1, all security is provided between end systems that implement IPSec.Sarthak Patel (
  26. 26. Combinations of Security Associations26For Case 2, security is provided only between gateways (routers, firewalls, etc.)and no hosts implement IPSec. This case illustrates simple virtual privatenetwork support.Sarthak Patel (
  27. 27. Combinations of Security Associations27Case 3 builds on Case 2 by adding end-to-end security. The same combinationsdiscussed for cases 1 and 2 are allowed here. The gateway-to-gateway tunnelprovides either authentication or confidentiality or both for all traffic between endsystems.Sarthak Patel (
  28. 28. Combinations of Security Associations28Case 4 provides support for a remote host that uses the Internet to reach anorganizations firewall and then to gain access to some server or workstation behindthe firewall.Sarthak Patel (
  29. 29. Key ManagementTwo types:Manual: A system administrator manually configures eachsystem with its own keys and with the keys of othercommunicating systems. This is practical for small, relativelystatic environments.29Automated: An automated system enables the on-demandcreation of keys for SAs and facilitates the use of keys in a largedistributed system with an evolving configuration.Oakley Oakley is a key exchange protocol based on the Diffie Hellmanalgorithm but providing added security.Internet Security Association and Key Management Protocol (ISAKMP)Sarthak Patel (
  30. 30. OakleyThree authentication methods:Digital signaturesPublic-key encryptionSymmetric-key encryption (aka. Preshare key)30 Sarthak Patel (
  31. 31. ISAKMP31 Sarthak Patel (
  32. 32. Email Securityemail is one of the most widely used and regarded networkservicescurrently message contents are not secure32 Sarthak Patel (
  33. 33. Email Security Enhancementsconfidentialityprotection from disclosureauthenticationof sender of messagemessage integrity33message integrityprotection from modificationnon-repudiation of originprotection from denial by senderSarthak Patel (
  34. 34. Pretty Good Privacy (PGP)Open source, freely available software package for secure e-mailde facto standard for secure emaildeveloped by Phil Zimmermannselected best available crypto algs to use34selected best available crypto algs to useRuns on a variety of platforms like Unix, XP, Macintosh andother systemsoriginally free (now also have commercial versions available)Sarthak Patel (
  35. 35. PGP Operation – Authentication1. sender creates message2. Generates a digital signature for the message3. use SHA-1 to generate 160-bit hash of message4. signed hash with RSA using senders private key, and isattached to message35attached to message5. receiver uses RSA with senders public key to decryptand recover hash code6. receiver verifies received message using hash of it andcompares with decrypted hash codeSarthak Patel (
  36. 36. PGP Operation – Confidentiality1. sender generates a message and encrypts it.2. Generates a128-bit random number as session key3. Encrypts the message using CAST-128 / IDEA / 3DESin CBC mode with session key4. session key encrypted using RSA with recipients public364. session key encrypted using RSA with recipients publickey and attached to the msg5. receiver uses RSA with private key to decrypt andrecover session key6. session key is used to decrypt messageSarthak Patel (
  37. 37. PGP Operation – Confidentiality &Authenticationcan use both services on the same messagecreate signature & attach it to the messageencrypt both message & signature37 Sarthak Patel (
  38. 38. PGP Operation – CompressionPGP compresses messages to save space for e-mailtransmission and storageby default PGP compresses message after signing butbefore encryptingso can store uncompressed message & signature for later38so can store uncompressed message & signature for laterverificationEncryption after compression strengthens security (becausecompression has less redundancy)uses ZIP compression algorithmSarthak Patel (
  39. 39. PGP Operation – Email Compatibilitywhen using PGP will have binary data (8-bit octets) tosend (encrypted message, etc)however email was designed only for texthence PGP must encode raw binary data into printableASCII characters39ASCII charactersuses radix-64 algorithmPGP also segments messages if too big(maximum length 50,000 octets)Sarthak Patel (
  40. 40. PGP Cryptographic FunctionsPGP Cryptographic FunctionsPGP Cryptographic FunctionsPGP Cryptographic Functions40 Sarthak Patel (
  41. 41. Ks =session key used in symmetric encryption schemePRa =private key of userA, used in public-key encryption schemePUa =public key of userA, used in public-key encryption scheme41EP = public-key encryptionDP = public-key decryptionEC = symmetric encryptionDC = symmetric decryptionH = hash function|| = concatenationZ = compression using ZIP algorithmR64 = conversion to radix 64ASCII formatSarthak Patel (
  42. 42. PGP Operation – Summary42 Sarthak Patel (
  43. 43. PGP Session Keysneed a session key for each messageof varying sizes: 56-bit DES, 128-bit CAST or IDEA, 168-bitTriple-DESuses random inputs43 Sarthak Patel (
  44. 44. PGP Message Format44 Sarthak Patel (
  45. 45. S/MIMES/MIMES/MIMES/MIMES/MIME (Secure/Multipurpose Internet MailExtension) is a security enhancement to the MIMEInternet e-mail format standard, based on technologyfrom RSA Data Security.RFC 82245RFC 822RFC 822 defines a format for text messages that are sentusing electronic mail. It has been the standard forInternet-based text mail message and remains incommon use.Sarthak Patel (
  46. 46. RFC HeaderDate:Tue, 16 Jan 1998 10:37:17 (EST)From: "William Stallings" <>Subject:The Syntax in RFC 822To: Smith@Other-host.com46Cc: Jones@Yet-Another-Host.comHello.This section begins the actual message body,which is delimited from the message heading by ablank line.Sarthak Patel (
  47. 47. Multipurpose Internet Mail ExtensionsMultipurpose Internet Mail ExtensionsMultipurpose Internet Mail ExtensionsMultipurpose Internet Mail ExtensionsMIME is an extension to the RFC 822 framework that isintended to address some of the problems and limitations ofthe use of SMTP (Simple Mail Transfer Protocol) or someother mail transfer protocol and RFC 822 for electronicmail.47mail.Sarthak Patel (
  48. 48. Overview S/MIMEOverview S/MIMEOverview S/MIMEOverview S/MIMEThe MIME specification includes the following elements:1. Five new message header fields are defined, which may beincluded in an RFC 822 header. These fields provide informationabout the body of the message.2. A number of content formats are defined, thus standardizing482. A number of content formats are defined, thus standardizingrepresentations that support multimedia electronic mail.3. Transfer encodings are defined that enable the conversion of anycontent format into a form that is protected from alteration bythe mail system.Sarthak Patel (
  49. 49. The five header fields defined in MIME are as follows:MIME-Version: Must have the parameter value 1.0. This field indicates that themessage conforms to RFCs 2045 and 2046.Content-Type: Describes the data contained in the body with sufficient detailthat the receiving user agent can pick an appropriate agent or mechanism torepresent the data to the user or otherwise deal with the data in an appropriate49represent the data to the user or otherwise deal with the data in an appropriatemanner.Content-Transfer-Encoding: Indicates the type of transformation that has beenused to represent the body of the message in a way that is acceptable for mailtransport.Content-ID: Used to identify MIME entities uniquely in multiple contexts.Content-Description: A text description of the object with the body; this isuseful when the object is not readable (e.g., audio data).Sarthak Patel (
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  51. 51. THE ENDSarthak Patel ( END