CryptKit

Why Client-Side Security is Crucial

In an era where data breaches make headlines weekly, the tools you use to protect your secrets should be as trustworthy as the secrets themselves. That is why CryptKit was built from the ground up to run entirely in your browser — no servers, no uploads, no compromises.

The Problem with Online Tools

Most online cryptography tools send your data to a server for processing. When you type a password into a “password strength checker” on a typical website, that password travels across the internet to someone else’s computer. Even if the site claims to process data securely, you have no way to verify what happens behind the scenes. Your sensitive inputs — passwords, private keys, encrypted messages — could be logged, stored, or worse.

This is not a hypothetical risk. Numerous popular online tools have been caught transmitting user input to third-party analytics services, ad networks, or their own backend databases. When you use a server-side tool, you are placing your trust in the operator’s infrastructure and their promises.

The CryptKit Difference: Your Browser Is the Only Computer Involved

Every tool on CryptKit uses the Web Crypto API, a set of cryptographic primitives built directly into modern web browsers. When you check your password strength, generate a secure password, or encrypt a message with AES, the computation happens locally on your device. Your input never leaves your machine. There is no server to compromise, no network request to intercept, and no database to breach.

This architecture also means CryptKit works offline (once loaded) and is immune to server-side outages. The source code is auditable, and the behavior you see is the behavior you get — no hidden processing pipelines.

What Makes a Strong Password?

A strong password is one that is difficult for an attacker to guess through brute force or dictionary attacks. The strength of a password is measured in entropy, expressed in bits. A password with higher entropy takes exponentially longer to crack. For example, a password with 60 bits of entropy would take centuries to crack even with modern hardware.

Use our Entropy Calculator to measure the strength of your existing passwords, and our Password Strength Checker to get actionable improvement suggestions. If you need to create a new password, the Password Generator produces cryptographically secure random passwords using your browser’s built-in random number generator.

For those who prefer memorable yet strong passwords, the Passphrase Generator creates Diceware-style passphrases from the EFF word list. A passphrase like “correct-horse-battery-staple” can be easier to remember than a random string of characters while providing comparable security.

Encryption, Hashing, and Encoding Explained

Encryption transforms data into an unreadable format that can only be reversed with the correct key. Our AES Encrypt/Decrypt tool uses AES-256-GCM, the same algorithm used by governments and security professionals worldwide. Keys are derived using PBKDF2, ensuring that even weak passwords produce strong encryption keys.

Hashing is a one-way transformation that produces a fixed-length output from any input. Unlike encryption, hashes cannot be reversed. They are commonly used to verify data integrity and store passwords securely. Generate SHA-256 or SHA-512 hashes instantly with our tools.

Encoding converts data into a format suitable for transmission or storage. Our Base64 Encode/Decode tool handles the most common encoding scheme used on the web, useful for embedding images in CSS, transmitting binary data in JSON, and working with APIs.

Authentication & Key Generation

Beyond passwords and symmetric encryption, CryptKit provides tools for message authentication and asymmetric cryptography. Generate HMAC codes to verify that messages haven't been tampered with, create RSA key pairs for public-key encryption, and explore BIP39 mnemonic generation to understand how deterministic seed phrases work. All computations run locally in your browser using the Web Crypto API.

Built for Speed, Privacy, and Trust

CryptKit is optimized for performance. Pages load in under 2.5 seconds, even on mobile devices with slow connections. We use minimal JavaScript, serve static HTML for search engine crawlers, and avoid heavy frameworks that slow down your experience. The result is a fast, accessible toolset that respects your time and your privacy.

No accounts. No cookies for tracking. No data collection. Just cryptography tools that work the way they should — privately, securely, and entirely in your hands.