Post on my personal blog: https://schuindtlog.wordpress.com/2014/06/25/how-to-use-openpgp-js-to-encrypt-and-decrypt-data/

openpgpjs_usage.js

// ##########################################
// GENERATING KEYS
// ##########################################
my_user_id = "John Test <john_test@someserver.com>";
my_passphrase = "123qwe"; // Key Pairs is always protected with a password to safety.
my_key = openpgp.generateKeyPair({numBits: 1024, userId: my_user_id, passphrase: my_passphrase});

// My Private Key String
console.log("My private key:\n\n" + my_key.privateKeyArmored + "\n\n");

// My Public Key String
console.log("My public key:\n\n" + my_key.publicKeyArmored + "\n\n");


// ##########################################
// ENCRYPTING MESSAGES
// ##########################################
// Let's supose that I sent my Public Key to a friend and he wants to encrypt a message to me.
// First I will store my public key string in a variable to make things clear.
my_public_key = my_key.publicKeyArmored; // It's the "John Test <john_test@someserver.com>" key pair.

// My friend has access to that string, so he will use it to encrypt the message.
// But now he needs to create a OpenPGP.js Object of that string by reading it in this way:
john_public = openpgp.key.readArmored(my_public_key);
// So now the whole OpenPGP.js library is available inside this object.
// We're going to use the library to encrypt a message with this key.
// Here is the message he wants to send me:
raw_message = "Hello, how are you? Did you changed your phone number?";
// And here is how to encrypt it:
encrypted_message = openpgp.encryptMessage(john_public.keys, raw_message);
// Check it on Console:
console.log("Encrypted message:\n\n" + encrypted_message + "\n\n");


// ##########################################
// DECRYPTING MESSAGES
// ##########################################
// Now I need to decrypt it once I have my private key stored in my key pair "my_key".
// But first I will create a OpenPGP.js Object of the encrypted message:
oepnpgp_encrypted_message = openpgp.message.readArmored(encrypted_message); // It reads encrypted strings.
// In order to have access to my private key object I need to "unlock" it by using the password defined before:
my_key.key.decrypt(my_passphrase); // It's really needed by the OpenPGP.js security standards.
// Finaly use my key pair to decrypt it, note I need to use "my_key.key" to reference my private key.
decrypted_message = openpgp.decryptMessage(my_key.key, oepnpgp_encrypted_message);
// Check it on Console:
console.log("Decrypted message:\n\n" + decrypted_message + "\n\n");