The Format Notebook

Short, practical notes on the formats and algorithms behind the tools: what each one does, and the detail that catches people out.

• Hashing vs Encryption: Understanding the Critical Differences
  This guide explains why hashing is a one-way process unlike encryption and identifies which algorithms are suitable for password storage and data integrity.
• How Word Counters Use Delimiters to Estimate Word Counts
  Discover how word counters rely on delimiters and whitespace for calculations, and why differences in punctuation or Unicode encoding lead to varied results.
• Preventing JWT Signature Bypass via the None Algorithm
  This guide explains how attackers use the alg none field in a JSON Web Token header to bypass signature verification and escalate privileges on a server.
• UUID Version 4 Uniqueness Depends on Cryptographic Entropy
  Explore why version 4 UUID collision probability depends on cryptographic entropy and how random primary keys impact B-tree index performance in databases.
• How Reed-Solomon Error Correction Keeps QR Codes Scannable
  This guide explains how Reed-Solomon error correction allows a QR code to remain scannable even with physical damage or logos by using redundant parity bits.
• Bcrypt Cost Factor: Exponential Scaling and Input Limits
  Learn how the bcrypt cost factor works, including its exponential growth, the seventy-two byte input limit, and how to manage hash security upgrades safely.
• Unix Time Leap Seconds and the Year 2038 Integer Overflow
  Learn how Unix time handles leap seconds and why the Year 2038 problem occurs due to signed 32-bit integer overflow in legacy systems and binary protocols.
• Base64 Encoding Explained: Mechanics and Data Bloat
  Learn how Base64 encoding transforms binary data into a text format for safe transport via email or data URLs, despite a thirty-three per cent size increase.