IB Computer Science Topic A2.4.4: Process of Encryption and Digital Certificates Key Definitions

Asymmetric cryptography gives each party a mathematically linked key pair: a public key that can be published to anyone and a private key that never leaves its owner. It solves key distribution but is far slower than symmetric cryptography.

A digital certificate is an electronic document that binds a public key to the identity of its owner. A certificate authority verifies that identity and signs the certificate, so a client can check the binding before trusting the key.

Encryption converts readable plaintext into unreadable ciphertext using an algorithm and a key. The process is reversible: the right key turns the ciphertext back into the original plaintext.

A session key is a symmetric key agreed at the start of one connection, used to encrypt that connection's data, and discarded when the connection ends.

Symmetric cryptography uses a single shared key to both encrypt and decrypt data. It is fast enough to protect the bulk of the traffic in a connection, but both parties must already hold the same secret key.