security requirements and attacks
DESCRIPTION
Security Requirements and AttacksTRANSCRIPT
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Network Security
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ContentsSecurity Requirements and AttacksConfidentiality with Conventional EncryptionMessage Authentication and Hash FunctionsPublic-Key Encryption and Digital SignaturesIPv4 and IPv6 Security
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Security RequirementsConfidentialityIntegrityAvailability
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Passive AttacksRelease of message content (eavesdropping)Prevented by encryptionTraffic AnalysisFixed by traffic paddingPassive attacks are easier to prevent than to detect
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Active AttacksInvolve the modification of the data stream or creation of a false data streamActive Attacks are easier to detect than to prevent
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Active Attacks (cont.)MasqueradeReplayModification of messagesDenial of service
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Conventional EncryptionPlain textEncryption algorithmDecryption algorithmPlain textTransmitted ciphertextShared secret key
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Conventional Encryption RequirementsKnowing the algorithm, the plain text and the ciphered text, it shouldnt be feasible to determine the key.The key sharing must be done in a secure fashion.
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Encryption AlgorithmsData Encryption Standard (DES)Plaintext: 64-bit blocksKey: 56 bitsHas been broken in 1998 (brute force)Triple DESAdvanced Encryption Standard (AES)Plaintext: 128-bit blocksKey: 128, 256 or 512 bits
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Location of Encryption DevicesPSNPSNPSNPSNPSNPacket Switching NodeEnd-to-end encryption deviceLink encryption device
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Key DistributionManualSelected by A, physically delivered to BSelected by C, physically delivered to A and BAutomaticThe new key is sent encrypted with an old keySent through a 3-rd party with which A and B have encrypted links
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Message AuthenticationAuthentic message means that: it comes from the alleged sourceit has not been modified
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Message Authentication ApproachesAuthentication with conventional encryptionAuthentication without message encryption:when confidentiality is not necessarywhen encryption is unpractical
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Message Authentication CodeUses a secret key to generate a small block of dataMACM = F (KAB, M)
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One-way Hash FunctionMessage digest a fingerprint of the messageLike MAC, but without the use of a secret keyThe message digest must be authenticated
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Secure Hash RequirementsH can be applied to a block of any sizeH produces a fixed-length outputH(x) is easy to computeGiven h, it is infeasible to compute x s.t. H(x) = hGiven x, it is infeasible to find y s.t. H(x) = H(y)It is infeasible to find (x,y) such that H(x) = H(y)
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Secure Hash FunctionsMessage Digest v5 (MD5)128-bit message digesthas been found to have collision weaknessSecure Hash Algorithm (SHA-1)160-bit message digest
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Public-Key EncryptionEach user has a pair of keys:public keyprivate keyWhat is encrypted with one, can only be decrypted with the other
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EncryptionPlain textPlain textTransmitted ciphertextBobs public keyAliceBobBobs private key
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AuthenticationPlain textPlain textTransmitted ciphertextAlices public keyAliceBobAlices private key
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Digital SignatureLike authentication, only performed on a message authenticator (SHA-1)
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Public-Key Encryption AlgorithmsRSA (used by PGP)El Gamal (used by GnuPG)
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Key ManagementPublic-Key encryption can be used to distribute secret keys for conventional encryptionPublic-Key authentication:signing authorityweb of trust
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IPv4 and IPv6 SecurityProvides encryption/authentication at the network (IP) layerIPSec applications:Virtual Private NetworkingE-commerceOptional for IPv4, mandatory for IPv6
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IP Header with IPSec Information
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Two Types of IPSec Security Protocols
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Advantages of IPSec
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How an AH is Generated in IPSec
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AH Fields
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The ESP Header FormatEncapsulated Security Payload
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Tunnel Versus Transport Mode
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AH Header Placement in Transport Mode
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AH Header Placement in Tunnel Mode
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ESP Header Placement in Transport Mode
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ESP Header Placement in Tunnel Mode
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Security AssociationOne-way relationship between two hosts, providing security services for the payloadUniquely identified by:Security Parameter Index (SPI)IP destination addressSecurity Protocol Identifier (AH/ESP)
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SA Security Parameters
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IPSec Process Negotiation
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Key ManagementManualused for small networkseasier to configureAutomatedmore scalablemore difficult to setupISAKMP/Oakley
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IKE Use in an IPSec Environment