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CYBERSECURITY (SECURING
DATA)
1. Password Storage and Hashing
Passwords should never be stored in plaintext. Storing credentials in a simple
username:password format makes systems vulnerable to theft and credential stuffing attacks.
Hashing: A one-way mathematical function that converts a password x into a fixed- length string f(x).
Security Benefits: Makes it computationally difficult to reverse-engineer original passwords and increases the cost for dictionary or brute-force attacks. Salting: Adding a unique, random value (salt) to each password before hashing: f(password, salt). This ensures identical passwords produce unique hashes, preventing Rainbow Table attacks. Modern Standards: SHA-2 and SHA-3 families are recommended for their high bit- rich output and resistance to collision.
2. Cryptography: Codes, Ciphers, and Keys
While Codes map entire words to symbols using a codebook, Ciphers are algorithmic transformations that operate on individual characters or bits using cryptographic keys.
Secret Key Cryptography (Symmetric Encryption)
Uses the same key for both encryption and decryption. Popular examples include the Caesar Cipher (simple) and AES or Triple DES (modern).
Lecture Notes: Principles of Cryptography & Data Protection
Term Description
Encryption Transforming plaintext into ciphertext using a key.
Decryption Reversing ciphertext back to plaintext using the same key.
Symmetric Key A single key shared by both the sender and the receiver.
Asymmetric Key Uses a mathematically linked pair of different keys.
3. Public Key Cryptography (Asymmetric Encryption)
This method uses a key pair : a Public Key (distributed openly) and a Private Key (kept strictly secret). Messages encrypted with a public key can only be decrypted by the corresponding private key.
RSA Algorithm: Relies on the mathematical difficulty of factoring large prime numbers p and q. Core Logic:
c = me^ mod n | m = cd^ mod n Where m = message, c = ciphertext, e/d = exponents, and n = pq. Diffie-Hellman: Enables two parties to establish a shared secret key over an insecure channel.
7. Summary of Cryptographic Processes
Process Mechanism
Password Creation Server salts and hashes the password for storage.
Symmetric Enc. Plaintext + Key → Ciphertext; Ciphertext + Same Key → Plaintext.
Asymmetric Enc. Plaintext + Public Key → Ciphertext; Ciphertext + Private Key → Plaintext.
Digital Signature Encrypting a message hash with a Private Key to prove identity.
Passkey Auth. Signing a server challenge using a device-stored Private Key.
Professional Lecture Notes • Cybersecurity Series • Data Security & Cryptography
