Encryption Tool

Features

• AES-256-GCM authenticated encryption
• PBKDF2-SHA-256 key derivation with a configurable work factor
• Random salt and IV generated for every message
• Self-contained output, salt and IV travel with the ciphertext
• Uses the browser's audited Web Crypto implementation

How to use it

1. Choose Encrypt and type your message.
2. Enter a long passphrase and press Encrypt.
3. Copy the whole output string and store it safely.
4. To reverse it, switch to Decrypt and supply the same passphrase.

How this works, and what it is not suitable for

AES-GCM is authenticated encryption: it provides confidentiality and integrity together. If a single bit of the ciphertext is altered, decryption fails outright rather than returning corrupted plaintext. That is why a wrong passphrase produces an error rather than garbage. A fresh 96-bit initialisation vector is generated for every message, which is essential, reusing an IV with the same key in GCM catastrophically breaks the cipher and can expose the key.

Your passphrase is not the key. It is stretched into one using PBKDF2 with a random 128-bit salt and, by default, 310,000 iterations of SHA-256, the figure OWASP currently recommends. The salt means two people with identical passphrases get different keys, and the iteration count makes brute-forcing the passphrase expensive. The strength of the whole scheme still rests on the passphrase: a short one falls to a dictionary attack regardless of the iteration count.

Be clear about the limits. This is a useful way to protect a note before emailing it or storing it somewhere you do not fully trust, but it is not a secure messaging system. There is no forward secrecy, no identity verification, and no safe channel here for sharing the passphrase, sending it alongside the ciphertext defeats the entire exercise. For ongoing private communication use a purpose-built tool like Signal or age, and for anything where lives or livelihoods depend on the secrecy, use software that has been formally audited.