Secure Note Encrypt / Decrypt
Encrypt a note with a passphrase, entirely in your browser.
Text to encrypt
Passphrase
How this works
A key is derived from your passphrase with PBKDF2-SHA256 at 600,000 iterations, then used to encrypt with AES-256-GCM. Three choices are worth explaining. A fresh random salt is generated per message, so the same passphrase does not produce the same key twice and precomputed tables are useless. A fresh random IV is generated too, so encrypting identical text twice produces different ciphertext — which stops an observer noticing that you sent the same thing again. And GCM authenticates as well as encrypts, so a modified message fails to decrypt rather than quietly producing wrong plaintext. The high iteration count exists because the passphrase is the weak link: everything above it is strong, and making derivation slow is the only lever against guessing.
What the results mean
- AES-256-GCM
- Authenticated encryption. Tampering is detected rather than producing garbage.
- PBKDF2, 600,000 iterations
- Deliberately slow key derivation, to make passphrase guessing expensive.
- Random salt and IV
- Per message. The same text and passphrase never produce the same ciphertext.
- Decryption failed
- Wrong passphrase or altered message. Indistinguishable on purpose.
Common problems and fixes
- I lost the passphrase
- The message is unrecoverable. That is the design rather than a limitation — anything that could recover it could also be compelled to.
- Decryption fails and I am sure the passphrase is right
- Check the ciphertext was copied completely, including any trailing characters. A truncated message fails authentication exactly like a wrong passphrase.
- I want to send someone a self-destructing link
- This is not that. Nothing is stored, so there is no link to create and nothing to destruct — you get ciphertext and choose how to deliver it.
Frequently asked questions
Is this actually secure?
The cryptography is standard and correctly applied: AES-256-GCM with a PBKDF2-derived key, random salt and IV per message. The security in practice is your passphrase, which is the part no algorithm can strengthen.
Why does the same text encrypt differently each time?
A fresh random IV per message. Without it, identical plaintext would produce identical ciphertext, which tells an observer you sent the same message twice — often more than enough to be useful to them.
Can you recover my message?
No. Nothing is transmitted or stored, and this page has no server side. There is nothing to recover from, which is the point.
Put this on your own site
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