Public-key cryptography solves a central problem of communication: how can people communicate securely without first sharing a secret key through a secure channel? This lesson introduces key pairs, one-way functions, and the historical development of asymmetric cryptography.
In symmetric cryptography, the sender and recipient use the same secret key to encrypt and decrypt messages. Both people must obtain the key securely before communicating. As the number of people grows, managing separate secret keys for every pair becomes difficult.
All flashcards
What is a public-key pair?
A mathematically related public key that may be shared and private key that its owner must protect.
What does a digital signature help establish?
It supports checking that a message is associated with the signing key and has not been altered.
What is a hybrid cryptosystem?
A system that uses public-key techniques to establish a symmetric key, then symmetric cryptography for data.
What role does PKI play?
It uses certificates to bind identities to public keys through a trusted certification system.
How can forward secrecy limit a key compromise?
Ephemeral session keys can reduce the impact of a later compromise of a long-term key.
Quiz questions
What does a digital signature primarily help a recipient check?Answer: Whether a message is associated with the signing key and remains unaltered.
In public-key encryption, which key does a sender use to encrypt a message for a recipient?Answer: The recipient's public key.
How does a hybrid cryptosystem typically protect bulk data?Answer: It uses symmetric cryptography with a session key established through public-key techniques.
How can substituting a public key enable a man-in-the-middle attack?Answer: An attacker can use the substituted key to create separate connections with both parties.
What does a certificate authority do in a public-key infrastructure?Answer: It issues certificates that associate identities with public keys.