Introduction to Cryptography

Cryptography Defined

• Cryptography uses mathematical algorithms.
• This transfers data into encrypted forms.
• This encrypted form makes the data unreadable by unauthorized users.

Core Cryptographic Concepts

• Plaintext/Cleartext is an unencrypted message.
• Ciphertext is encrypted message.
• Algorithms are processes that encrypt and decrypt messages.
• Cryptanalysis is the art of cracking cryptographic systems.

Encryption vs Decryption

• Encryption converts plaintext to ciphertext.
• Decryption converts ciphertext back to plaintext.

Cryptography and the CIA Triad

• Cryptography maintains confidentiality by encrypting data, and keeping it private.
• It helps ensure integrity by detecting unauthorized data changes.
• Cryptography indirectly preserves data availability.
• Non-repudiation is achieved by proving the origin/authenticity of messages.
• This prevents denial of involvement in transactions.

Symmetric Encryption

• Symmetric encryption uses the same key for both encryption and decryption.
• It's efficient and fast when encrypting large amounts of data.
• Common symmetric encryption algorithms include AES and DES.
• Symmetric encryption is used for confidentiality.

Asymmetric Encryption

• Asymmetric encryption uses a pair of keys: public and private.
• Data encrypted with the public key requires a corresponding private key to decrypt it, and vice versa.
• It is slower than symmetric encryption.
• Offers key distribution and digital signature advantages.
• Common asymmetric encryption algorithms are RSA and ECC.

Key Length

• Key length specifies the size of the cryptographic key in encryption algorithms.
• Longer key lengths offer more security against attacks.
• This increased security is due to the higher number of possible keys that would be needed to break the encryption.

Hashing

• Hashing converts input data into a fixed-size string of characters.
• Hashing algorithms are used to prove data integrity.

Applications of Hashing

• Hashing verifies data integrity during transmission.
• Password storage utilizes hash functions for security.
• Password hash values are stored rather than the passwords themselves.
• Hashes are compared upon user login.
• Hashing generates digital signatures, by creating a unique identifier, and then encrypting that hash with a private key.
• Hashing's role is crucial in blockchain technology, where each block integrates a hash, and creates resistance to tampering.

Hash Algorithm Implementations

• Secure Hash Algorithm (SHA) is considered a stronger algorithm.
• The most popular variant is SHA256, and it produces a 256-bit digest.
• Message Digest Algorithm #5 (MD5) produces a 128-bit digest.
• MD5 may be required for compatibility between security products.

Digital Signatures Explained

• Digital signatures authenticate the identity of the sender.
• Digital signatures are used to ensure the integrity of digital messages and documents.
• Provide evidence that the sender cannot deny sending the message.

Public Key Infrastructure (PKI)

• PKI enables secure communications over untrusted networks.
• PKI uses digital certificates, encryption, and authentication services.
• It allows secure information exchanges and verification.
• Uses public and private key pairs.

Key Components within PKI

• Digital Certificates
• Public Key Cryptography
• Certificate Authorities (CAs)
• Certificate Lifecycle Management
• Key Management
• Trust Models
• Certificate Revocation
• Certificate Policies and Practices
• PKI Architecture
• Secure Communication Protocols
• Identity and Access Management
• PKI Standards and Protocols