Please enable JavaScript.
Coggle requires JavaScript to display documents.
Information Security — Sessional II - Coggle Diagram
Information Security — Sessional II
Classical Ciphers
Substitution — replace symbols
Monoalphabetic — one fixed substitution alphabet
Caesar / ROT13
Affine Cipher
Polyalphabetic — multiple substitution alphabets
Vigenère Cipher
Transposition — rearrange symbol positions
Rail Fence
Columnar Transposition
Important Concepts
Plaintext, Ciphertext and Key
Encryption and Decryption
Keyspace and Brute Force
Frequency Analysis
Modern Cryptography
DES — Symmetric Block Cipher
Block Size — 64 bits
Effective Key Size — 56 bits
16 Feistel Rounds
Main Tables
IP — Initial Permutation
IP⁻¹ / FP — Final Permutation
E — Expansion Table: 32 → 48 bits
S-Boxes — Substitution: 48 → 32 bits
P — Permutation after S-Boxes
PC-1 — Key Permutation: 64 → 56 bits
PC-2 — Subkey Selection: 56 → 48 bits
Left-Shift Schedule
Round Operations
Expand Right Half
XOR with Round Key
S-Box Substitution
P Permutation
XOR with Left Half
Exchange Halves
Key Schedule
Split into Two 28-bit Halves
Circular Left Shifts
Generate 16 Round Keys
Decryption
Same Feistel Structure
Reverse Key Order: K16 → K1
AES — Symmetric Block Cipher
Block Size — 128 bits
State — 4 × 4 Byte Matrix
Key Sizes and Rounds
128-bit Key — 10 Rounds
192-bit Key — 12 Rounds
256-bit Key — 14 Rounds
Initial Step
AddRoundKey
Main Round Operations
SubBytes — S-Box Substitution
ShiftRows — Cyclic Row Shifts
MixColumns — Arithmetic in GF(2⁸)
AddRoundKey — XOR with Round Key
Final Round
SubBytes
ShiftRows
AddRoundKey
No MixColumns
Key Expansion
RotWord
SubWord
Rcon — Round Constants
XOR Operations
Decryption Operations
InvShiftRows
InvSubBytes
AddRoundKey
InvMixColumns
Important Concepts
Confusion and Diffusion
Avalanche Effect
Finite-Field Multiplication
RSA — Asymmetric Cryptography
Public and Private Keys
Key Generation
Choose Primes p and q
n = p × q
φ(n) = (p − 1)(q − 1)
Choose e Coprime to φ(n)
d = Modular Inverse of e
Textbook Operations
Encryption: C = Mᵉ mod n
Decryption: M = Cᵈ mod n
Message Range: 0 ≤ M < n
Key Usage
Encrypt — Receiver’s Public Key
Decrypt — Receiver’s Private Key
Sign — Sender’s Private Key
Verify — Sender’s Public Key
Important Concepts
Integer Factorization
Textbook RSA Multiplicative Property
OAEP — Encryption Padding
PSS — Signature Encoding
Diffie–Hellman — Key Agreement
Public Parameters
Prime Modulus p
Generator g
Private Exponents
Alice — a
Bob — b
Public Values
A = gᵃ mod p
B = gᵇ mod p
Shared Secret
S = Bᵃ mod p = Aᵇ mod p
Key Derivation Function → Session Keys
Important Concepts
Discrete Logarithm Problem
Unauthenticated DH → MITM Risk
DHE — Fresh Ephemeral Exponents
Forward Secrecy
Key Agreement, Not Message Encryption
Cryptographic Systems
Security Goals
Confidentiality
Integrity
Authentication
Non-Repudiation
Negotiation
Agree on Algorithms
Cipher Suite Selection
Authentication
Passwords and Shared Secrets
Challenge–Response
Fresh Nonce
Replay Protection
Digital Signatures
Hash, Then Sign
Verify with Public Key
PKI and Certificates
Certificate Authority — CA
Identity Bound to Public Key
Signature and Trust Chain
Validity Dates
Hostname Matching
Revocation — OCSP / CRL
Key Establishment
DH / DHE / ECDHE
Pre-Shared Keys — PSK
Derive Symmetric Session Keys
Forward Secrecy
Ongoing Secure Communication
Symmetric Encryption
Block Cipher Modes
ECB
CBC
CTR
Hash Functions
Preimage Resistance
Second-Preimage Resistance
Collision Resistance
MAC / HMAC
Integrity and Shared-Key Authentication
AEAD — AES-GCM
Confidentiality and Integrity
Authentication Tag
Associated Data
Unique Nonce for Each Key
Digital Signatures
Public Verification
Support for Non-Repudiation
Examples
TLS — Secure Client–Server Communication
Signal Protocol — End-to-End Messaging
Database Security
Why Encryption Alone Is Insufficient
Secure Channel Can Carry Malicious Input
Application and Query Security Still Matter
SQL Injection
Untrusted Input Changes Query Meaning
Boolean Tests — True / False Conditions
UNION-Based Extraction
Error-Based Extraction
Inference Attacks
Derive Sensitive Facts from Allowed Results
Combine Queries or Aggregate Statistics
Database Protection
Parameterized Queries
Input Validation
Least-Privilege Database Accounts
Safe Error Handling
Encryption at Rest and in Transit
Logging and Auditing
Backups and Recovery