Free tool · public-key encryption
RSA encryption with public and private keys
With RSA, anyone can encrypt a message using your public key, but only your private key can decrypt it, so no password ever has to be shared. Generate a key pair here, give the public key to people who write to you, and keep the private key safe. Messages of any length work, and you can sign text too. Keys are created and used in your browser; nothing is uploaded.
How to use the tool
- 1
Generate a key pair
Choose 2048 or 4096 bits and tap Generate. Download both PEM files and keep the private one somewhere safe.
- 2
Share your public key
Send the public key (it starts with BEGIN PUBLIC KEY) to anyone who wants to send you something private.
- 3
Encrypt with a public key
On the Encrypt tab, paste the recipient’s public key and the message. Copy or share the qskr1. result.
- 4
Decrypt with your private key
On the Decrypt tab, paste your private key and the encrypted text to read the original message.
QRScanKaro
Just sharing a secret once?
For a quick private message to a friend, Text Encryption is simpler: lock it with a password, no keys to manage.
Encrypt with a password →Frequently asked questions
Is there a limit on message length?
RSA on its own can encrypt only a little: 190 bytes with a 2048-bit key (about 190 English letters or 60 Hindi letters) and 446 bytes with 4096-bit. For longer text the tool encrypts the message with a random AES-256-GCM key and encrypts only that key with RSA. This hybrid method is how HTTPS and PGP work, and it happens automatically.
What happens if someone gets my private key?
They can decrypt every message encrypted for your public key and sign messages as you. Never paste it into chats or emails, and store it offline or in a password manager. If it leaks, make a new pair and ask people to use the new public key.
Which RSA settings does it use?
RSA-OAEP with SHA-256 for encryption, public exponent 65537, and standard PEM keys (SPKI for the public key, PKCS#8 for the private key). Signatures use RSA-PSS with SHA-256. The keys also work with OpenSSL, Node, Python and Java.
Can I use keys made with OpenSSL?
Yes, if they are RSA keys in PEM format: BEGIN PUBLIC KEY, BEGIN PRIVATE KEY and the older BEGIN RSA PUBLIC / PRIVATE KEY all work. Remove any passphrase from the private key first. OpenSSH keys (ssh-rsa) and certificates need converting.
Are my keys stored anywhere?
No. Keys exist only in this browser tab until you download them. Refreshing the page clears them, and nothing is sent to QRScanKaro.
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