1.3 Practical Cryptography

Question 1

Cryptography is used for….

Two main types…..

Answer 1

Cryptography is used for confidentiality, integrity, and non-repudiation of data.
Symmetric and asymmetric cryptography are the two main types.

Question 2

Symmetric Cryptography

Answer 2

Uses the same key for encryption and decryption.
Efficient and fast, but key management can be complex.
Common algorithms: AES, DES, 3DES.
Operates in block cipher or stream cipher mode.

Question 3

Asymmetric Cryptography

Answer 3

Uses a mathematically related public-private key pair.
More secure for key exchange and digital signatures, but slower.
Common algorithms: RSA, Diffie-Hellman, Elliptic Curve Cryptography (ECC), DSA.

Question 4

Encryption Levels

Answer 4

Full disk encryption protects all user data on a device.
Partition encryption protects specific disk partitions.
File-level encryption protects individual files.
Volume/block encryption protects a section of the physical drive.
Database encryption protects data stored in databases.

Question 5

Hashing, Salting, and HMACs

Answer 5

Hashing creates a fixed-length digest from variable-length data.
Salting adds random data to a hash function to make it harder to crack.
HMACs are used for message integrity and origin authentication with a shared secret key.

Question 6

Key Exchange

Answer 6

Traditionally a challenge due to the need for secure key distribution.
Asymmetric key exchange algorithms (e.g., Diffie-Hellman) are commonly used.
Ephemeral Diffie-Hellman provides perfect forward secrecy.
Elliptic Curve Diffie-Hellman is efficient for mobile devices and IoT.

Question 7

Digital Signatures and Certificates

Answer 7

Digital signatures use public/private key pairs for authenticity, integrity, and non-repudiation.
Common hashing algorithms: SHA-1, SHA-2, SHA-3.
Common signing algorithms: RSA, DSA, Elliptic Curve DSA.
Digital certificates bind public keys to entities using a trusted third-party (CA).
X.509 standard defines the format for digital certificates.

Question 8

Public Key Infrastructure (PKI)

Answer 8

PKI is a framework for managing public keys and digital certificates with a trusted CA.
Certificate authorities (CAs) issue, manage, and revoke certificates.
Certificate Signing Request (CSR) is used to request a certificate from a CA.
Certificate Revocation Lists (CRLs) and Online Certificate Status Protocol (OCSP) are used to check certificate validity.
Different trust models exist for CAs (e.g., single CA, hierarchical).