Security

One-time passwords (OTPs) are short-lived authentication codes used to verify a user or transaction and help prevent account takeover and replay attacks by being valid for only a single use or a narrow time window[1][4]. This article explains the cryptographic foundations, standardized algorithms (HOTP and TOTP), delivery methods, security tradeoffs, implementation considerations, and best practices—plus links to authoritative resources you can consult for implementation details and standards[3][4][9]. Table of contents Introduction OTP fundamentals: what an OTP is and why it helps Core algorithms: HOTP and TOTP (how they work step-by-step) Other OTP flavors and delivery channels Security considerations and common attacks Implementation guidance and developer checklist User experience and operational concerns Further reading and authoritative resources Conclusion OTP fundamentals: what an OTP is and why it helps Definition: An OTP is a code generated for a single authentication event or a short time window; once used or expired it cannot be reused[1][3]. Purpose: OTPs add a possession factor to authentication—something the user has (device, phone, token)—complementing something they know (password) and reducing the impact of leaked static passwords[1][3]. Typical properties: short numeric or alphanumeric codes (commonly 6 digits), cryptographically derived from a shared secret plus a moving factor (counter or time), and validated server-side without storing reusable credentials[3][4]. Core algorithms: HOTP and TOTP Both HOTP and TOTP are standardized, widely used, and form the basis of most OTP systems. ...

Introduction Redis Access Control Lists (ACLs) let you define who can do what across commands, keys, and channels. Introduced in Redis 6 and expanded since, ACLs are now the standard way to secure multi-tenant applications, microservices, and administrative workflows without resorting to a single, global password. In this guide, you’ll learn how Redis ACLs work, how to design least-privilege access for different use cases, how to manage ACLs safely in production (files, replication, rotation), and how to audit and test your permissions before you deploy. ...

Introduction Bitcoin apps have evolved far beyond simple send-and-receive wallets. Today’s ecosystem includes secure self-custody wallets, Lightning Network payment apps, merchant point-of-sale systems, full nodes and infrastructure tools, privacy and multisig coordinators, tax and portfolio software, and developer SDKs. This guide provides a comprehensive, practical overview to help you choose, set up, and safely use Bitcoin apps depending on your goals—whether you’re a newcomer, a merchant, a power user, or a developer. ...

Introduction Webhooks are the backbone of modern, event-driven integrations. Instead of continuously polling an API to ask “has anything changed yet?”, webhooks let services push events to your application as soon as they happen: a payment succeeds, a repository receives a push, a customer updates their profile, or a ticket is assigned. This in-depth tutorial will take you from zero to hero. You’ll learn: What webhooks are and how they compare to polling and WebSockets How to build robust webhook receivers in multiple languages Signature verification, replay protection, and other security best practices Idempotency and reliable processing with retries and dead-letter queues How to test locally using tunnels and inspector tools How to design and operate your own webhook provider at scale Links to the best official docs and tools in the ecosystem If you’re implementing webhooks for the first time or trying to harden your production setup, this guide will meet you where you are and help you ship with confidence. ...

What is SSH in Simple Terms? Think of SSH keys like a secure key and lock system for your computer to talk to GitHub: Private Key = Your actual house key (keep it secret!) Public Key = A copy of your lock that you give to GitHub When you connect, GitHub tests your key in their lock - if it fits, you’re in! Step-by-Step Setup (5 minutes) 1. Create Your SSH Key ssh-keygen -t ed25519 -C "your_email@example.com" # Press Enter 3 times (uses default locations, no password) # Creates two files: id_ed25519 (private) and id_ed25519.pub (public) 2. Add Key to SSH Agent # Start the SSH agent eval "$(ssh-agent -s)" # Add your private key ssh-add ~/.ssh/id_ed25519 3. Add Public Key to GitHub # Copy your public key to clipboard cat ~/.ssh/id_ed25519.pub | pbcopy # macOS # OR cat ~/.ssh/id_ed25519.pub | xclip -selection clipboard # Linux Then: ...