Chapter 3: Introduction to Technological Aspects of Privacy
Encryption: Symmetric, Asymmetric, Certificates and PKI
Encryption shields data by converting plaintext to ciphertext using a key. Symmetric key cryptography uses one shared key (fast but sharing is hard); asymmetric cryptography uses public/private key pairs that scale and enable digital certificates via a certificate authority (CA) and public key infrastructure (PKI).
Encryption converts plaintext to ciphertext and is reversed with a key. Shielding can be encryption in transit (against 'man in the middle' attacks), at rest (a stolen encrypted hard drive stays secure - and under most data breach laws encryption at rest creates an exception from the duty to report a breach), or in use.
Symmetric vs asymmetric cryptography
Approach
Keys
Trade-off
Symmetric key cryptography
One shared key to encrypt and decrypt
Fast and short, but Alice must securely share the key with Bob
Asymmetric cryptography
Public + private key pair per user
Scalable - encrypt with the recipient's public key; basis for digital certificates
🔑 Certificates, CAs and PKI
A certificate authority (CA) validates identity and issues a digitally signed certificate linking a person to a public key. Public key infrastructure (PKI) is the broader system of policies, standards, people, and systems supporting key distribution and identity validation.
Key terms - quick answers
What is “Encryption”?
A reversible process that converts plaintext into scrambled ciphertext; decryption reverses it using a key.
What is “Plaintext”?
The original, readable data before encryption.
What is “Ciphertext”?
Scrambled, unreadable data produced by encrypting plaintext.
What is “Key”?
A string of characters applied by a cryptographic algorithm; the longer and more complex, the stronger the security.