Information Security in Python

Explore symmetric cipher structure, contrasting traditional ciphers (modular arithmetic, substitutions) with modern ciphers (algebraic structures, modes), and review attacks (brute force, differential cryptanalysis) and algorithms like DES, IDEA, and Blowfish.

Explore modular arithmetic basics, including the modulo operator, remainders, residue classes z_n, and congruence, with practical examples like clock arithmetic and simple addition and multiplication tables.

Learn additive cipher basics, including additive inverse and modular 26 decryption, and explore multiplicative cipher with multiplicative inverse for encryption and decryption in Python.

Explore the affine cipher in Python by combining multiplicative and additive steps with two keys, and encrypt/decrypt using mod 26 inverses.

Explore the one time pad cipher, a perfect secrecy algorithm that encrypts each symbol with a randomly chosen key from a large domain, yielding unbreakable communication when randomness is perfect.

Learn to implement a Caesar additive cipher in Python using lambda and map, converting characters to ASCII via ordinal values and applying mod 26 for encryption and decryption.

Explore the autokey cipher, a dynamic substitution cipher where each plaintext character shifts by the previous plaintext, with encryption and decryption functions demonstrated using ordinal, ASCII, and Caesar-style shifts.

Learn how modern block ciphers use n-bit blocks and k-bit keys, pad messages, and favor substitution over transposition, with a teaser on s-box and p-box.

Explore modern symmetric ciphers: feistel and non-feistel structures, using s-boxes, xor, and round keys to enable encryption and decryption, with examples like des and advanced encryption standard.

Understand sd es, a simplified des variant with 8-bit plaintext and 10-bit key, two rounds, key generation via p10/p8, the round function with expansion, s-boxes, and initial permutation.

Learn cipher feedback mode (CFB), output feedback mode (OFB), and counter mode (CTR) as stream ciphers that XOR IV-derived bits with plaintext, using shift registers or counters.

Explore algebraic structures in information security, focusing on groups, rings, and fields (including Galois fields), with examples like integers and permutation groups, and key properties: closure, associativity, identity, and inverses.

Explore algebraic structures by examining rings and fields, including closure, associativity, identity and inverse properties, and finite Galois fields GF(p^n) with practical examples.

Learn des3 in pycrypto by using 8-byte blocks and experimenting with 64-, 128-, and 192-bit keys, encrypting and decrypting a user input string.

learn how to decrypt ransomware by loading an existing key and iv from a key file, then apply a decryption function to restore the original files.

Learn aes-cbc mode by generating a 16-byte key and iv, padding plaintext, encrypting to ciphertext, and using base64 and json dumps to transmit and decrypt securely.

Master AES counter mode by encrypting and decrypting data with a 16-byte key and a counter; handle Base64 encoding/decoding and ciphertext to reveal plaintext.

Explore asymmetric ciphers with public and private keys for encryption and decryption, and their use in digital signatures and SSL, including RSA, ElGamal, and elliptic curve schemes.

Explore prime numbers and Euler's totient function and their roles in asymmetric encryption, including primality testing, sieve of Eratosthenes, modular arithmetic, and phi formulas for prime powers and composites.

Select larger p and q, compute n and phi(n), choose e and derive d to form public and private RSA keys; RSA encrypts a hash or signature, not the message.

Explore how message integrity, authentication, and non-repudiation safeguard communications, using encryption, hash functions, and HMAC to prevent masquerade, content and timing modifications in apps like e-commerce and banking.