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The CTF Recipes
  • Introduction
  • Cryptography
    • Introduction
    • General knowledge
      • Encoding
        • Character encoding
          • ASCII
          • Unicode
          • UTF-8
        • Data encoding
          • Base16
          • Base32
          • Base64
      • Maths
        • Modular arithmetic
          • Greatest Common Divisor
          • Fermat's little theorem
          • Quadratic residues
          • Tonelli-Shanks
          • Chinese Remainder Theorem
          • Modular binomial
      • Padding
        • PKCS#7
    • Misc
      • XOR
    • Mono-alphabetic substitution
      • Index of coincidence
      • frequency analysis
      • Well known algorithms
        • 🔴Scytale
        • 🔴ROT
        • 🔴Polybe
        • 🔴Vigenere
        • 🔴Pigpen cipher
        • 🔴Affine cipher
    • Symmetric Cryptography
      • AES
        • Block Encryption procedure
          • Byte Substitution
          • Shift Row
          • Mix Column
          • Add Key
          • Key Expansion / Key Schedule
        • Mode of Operation
          • ECB
            • Block shuffling
              • Challenge example
            • ECB Oracle
              • Challenge example
          • CBC
            • Bit flipping
              • Challenge example
            • Padding oracle
              • Challenge example
          • OFB
            • Key stream reconstruction
            • Encrypt to Uncrypt
  • 🛠️Pwn
    • General knowledge
      • STACK
        • Variables storage
        • Stack frame
      • PLT and GOT
      • HEAP
        • HEAP operations
        • Chunk
        • Bins
        • Chunk allocation and reallocation
      • Syscall
    • Architectures
      • aarch32
        • Registers
        • Instruction set
        • Calling convention
      • aarch64
        • Registers
        • Instruction set
        • Calling convention
      • mips32
        • Registers
        • Instruction set
        • Calling convention
      • mips64
        • Registers
        • Instruction set
        • Calling convention
      • x86 / x64
        • Registers
        • Instruction set
        • Calling convention
    • Stack exploitation
      • Stack Buffer Overflow
        • Dangerous functions
          • gets
          • memcpy
          • sprintf
          • strcat
          • strcpy
        • Basics
          • Challenge example
        • Instruction pointer Overwrite
          • Challenge example
        • De Bruijn Sequences
        • Stack reading
          • Challenge example
      • Format string
        • Dangerous functions
          • printf
          • fprintf
        • Placeholder
        • Data Leak
          • Challenge example
        • Data modification
          • Challenge example
      • Arbitrary code execution
        • Shellcode
        • ret2reg
        • Code reuse attack
          • Ret2plt
          • Ret2dlresolve
          • GOT Overwrite
          • Ret2LibC
          • Leaking LibC
          • Ret2csu
          • Return Oriented Programming - ROP
          • Sigreturn Oriented Programming - SROP
          • Blind Return Oriented Programming - BROP
            • Challenge example
          • 🔴Call Oriented Programming - COP
          • 🔴Jump Oriented Programming - JOP
          • One gadget
        • Stack pivoting
    • 🛠️Heap exploitation
      • Heap overflow
        • Challenge example
      • Use after free
        • Challenge example
      • 🛠️Double free
      • 🔴Unlink exploit
    • Protections
      • Stack Canaries
      • No eXecute
      • PIE
      • ASLR
      • RELRO
    • Integer overflow
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  1. Cryptography

Introduction

Cryptography is the practice of secure communication. It uses mathematical algorithms (ciphers) to encrypt and decrypt messages to ensure privacy and confidentiality.

In Capture the Flag events, cryptography challenges often involve breaking or reverse engineering systems to retrieve a hidden flag or secret message.

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Last updated 2 years ago