Network security

Từ vựng

English	Ý nghĩa
MAC/mæk/	MAC
TLS/ˌtiː el ˈes/	A protocol that protects data in transit using encryption, integrity checks and peer authentication.
symmetric/sɪˈmetrɪk/	Having corresponding parts or relationships that remain equivalent under a specified transformation or interchange.
asymmetric/ˌeɪsɪˈmetrɪk/	In cryptography, describing methods that use a related public key and private key rather than one shared secret key.

English

The three properties

Confidentiality needs encryption; integrity needs a MAC; authentication needs a certificate chain to a root the client already trusts. Drop any one and the protocol fails differently: no encryption is a wiretap, no MAC is alteration, no certificate is an impostor.
TLS layers them: symmetric for the data (fast), asymmetric for the key agreement (one expensive operation), certificates for identity.

{exercise:uni-cs0906-props}

Luyện tập

Integrity without confidentiality still —

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English

ClientHello (suites + fresh random), ServerHello (chosen suite + random) with certificate, key exchange (premaster under the public key), both derive session keys from the three values, Finished messages verify — then data flows symmetric-encrypted.
One RSA-style operation, then stream-speed cryptography: the asymmetry is used only to agree on the symmetric key.

{exercise:uni-cs0906-handshake}

Luyện tập

TLS uses asymmetric cryptography —

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English

Passive sniffing: defeated by encryption. Modification: defeated by the MAC (Finished catches handshake tampering). Impersonation: defeated by certificates. Handshake replay: defeated by the fresh randoms.
Encrypting without authenticating gives you a secure channel to the wrong machine; HTTPS makes the channel private and the server identified — the content can still lie.

{exercise:uni-cs0906-attacks}

Luyện tập

Handshake replay is defeated by —

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