A message only the right person can read
CryptoPad turns a short text into ciphertext that only its addressee can open, and turns ciphertext sent to you back into readable text. It all happens on your phone: no account, no server, no network access.
eyJhbGciOiJBRVMtMjU2LUdDTStYMjU1MTkiLCJpdiI6ImQ0d0h6YjdBREpSQXVabkciLCJlcGsiOiJNQ293QlFZREsyVnVBeUVBZGJTcmdMZ3pWeHJaNWdQeDRqZ1JVREUvNWw5ZklVa2dINFVyZzd2R2N6WT0iLCJjdCI6IitDRlg4K2VhUjN3Z1JoTDFUZmhEcmtZOWpKc2xpcCtwODV3WDZCYkd6SU5ndS85bFNKWW1YUU9wbC9JQUJzYWRHNnc9In0=How it works
Make a key pair
CryptoPad creates it on your phone. The private part stays there and is never shown or copied out; the public part is the one you give to people.
Swap public keys
Send your public key through any messenger or email — it is safe to share, because all it can do is lock messages for you. Add the public keys of the people you write to as contacts.
Encrypt and decrypt by copy and paste
Pick a contact, type on the Pad and tap Encrypt, then paste the result into any chat. To read a reply, paste it on the Pad and tap Decrypt.
What it does not do
- No network access. The app never connects to the internet; on Android it does not even ask for the permission.
- No account and no sign-up. No analytics, crash reporting, ads or tracking.
- No cloud and no sync. The app never copies a private key out and never puts one on the clipboard; only public keys and ciphertext are copied out. On iPhone private keys sit in the Keychain, tied to that device; on Android they are stored encrypted under a key that cannot leave the device.
- No way back for a lost key. If you delete a key, or the app, messages encrypted for that key can no longer be opened. Nobody has a copy — including us.
Under the hood
Each message is sealed with a fresh AES-256-GCM key, and that key is locked for the recipient with RSA-OAEP-256, ECDH on P-256 or X25519, depending on the type of their key. Only the cryptography built into the system is used: CryptoKit and Security on iPhone, the platform providers on Android.
Keys are standard PEM, and a message is a single line of base64 text, so it survives any messenger, email or note that carries text.
iPhone and Android
CryptoPad is made for iPhone (iOS 17 or later) and Android (7.0 or later). The two apps speak the same format: a message encrypted on one opens on the other, and a public key copied from one is accepted on the other. X25519 keys need Android 13 or later; RSA and P-256 keys work on every supported Android version.