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Viruses

Viruses. Normal executable. Infected executable. Entry. Entry. Sequence of program instructions. Jump. Original program. Replication and payload. Global Internet. Public hosts. Firewall. Bastion hosts. Second firewall. Internal hosts. Protected enclave.

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Viruses

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  1. Viruses Normal executable Infected executable Entry Entry Sequence of program instructions Jump Original program Replication and payload

  2. Global Internet Public hosts Firewall Bastion hosts Second firewall Internal hosts Protected enclave

  3. Communication Goals • Remote authentication • Based on something you know • Message confidentiality • Even if adversary eavesdrops • Message integrity • Even if adversary intervenes • Message non-repudiation • Even if sender changes her mind

  4. Key (bit string) Very complicated encryption algorithm Message (bit string) Encrypted message (bit string)

  5. Message Locking key (Identical) unlocking key Symmetric lock and key (Different) unlocking key Locking key Asymmetric lock and key

  6. Recipient opens using unlocking key Put message in lockbox Close and lock using sender’s locking key Symmetric case Transport to recipient Asymmetric case Locking and unlocking keys are different

  7. P = plaintext 0 n-1 Decrypt Encrypt C = Ps mod n P = Ct mod n t cannot be computed from (n,s) in reasonable time RSA asymmetric algorithm C = ciphertext

  8. Confidentiality Alice (sender) Bob (recipient) Bob must possess a secret not available to anyone else

  9. Confidentiality (con’t) Alice (sender) Bob (recipient) Alice must be able to transform the message so that only the person possessing that secret can read it Bob must possess a secret not available to anyone else

  10. Confidentiality (con’t) Alice (sender) Bob (recipient) Alice must be able to transform the message so that only the person possessing that secret can read it Bob must possess a secret not available to anyone else or Encrypt Decrypt

  11. Where to do encryption

  12. Non-repudiation Alice (sender) Bob (recipient) Bob must be able to verify the signature using public information Alice must sign the message using a secret not revealed to anybody else

  13. Authentication Alice (sender) Bob (recipient) Alice must possess a secret not available to anyone else

  14. Authentication (con’t) Alice (sender) Bob (recipient) Alice must possess a secret not available to anyone else Bob must be able to verify that Alice possesses that secret without Alice revealing it on the network or to Bob

  15. Authentication (con’t) Alice (sender) Bob (recipient) Alice must possess a secret not available to anyone else Bob must be able to verify that Alice possesses that secret without Alice revealing it on the network (and possibly not to Bob) or Challenge Response

  16. Digital certificate CA_ID (ID,public_key) Encrypted with CA private_key Certificate authority (CA) certifies (ID,key) binding

  17.  Alice provides Bob with a replica of her digital certificate, which provides and certifies Alice’s public key Bob Alice  Alice convinces CA of her identity  CA gives digital certificate and secret key to Alice  Bob verifies CA signature using CA public key CA

  18. Chain of trust Certificate authority Bank’s certificate issued by CA Merchant’s certificate issued by bank Authority’s known public key Merchant’s public key Bank’s public key Verify signature Verify signature

  19. Consumer electronic commerce CA Customer (client) Trusting CA public key, client can obtain authenticated public key of a seller Seller (server)

  20. Client can authenticate server using challenge response protocol Customer (client) Client can generate a random, secret “session key” and send confidentially to server Seller (server)

  21. Customer (client) Client and server can communicate confidentially Seller (server)

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