Add binary message helpers (#61)

* Add EncryptBinaryMessageArmored helper function to generate an armored PGP message given binary data and an armored public key

* Add DecryptBinaryMessageArmored helper function to decrypt armored PGP message into binary data

* Streamline the code and fix naming pattern + tests

helper/helper_test.go

@@ -130,3 +130,27 @@ func TestAttachmentEncryptionVerification(t *testing.T) {
 
 	assert.Exactly(t, attachment, decrypted)
 }
+
+func TestArmoredBinaryMessageEncryption(t *testing.T) {
+	plainData := []byte("Secret message")
+
+	armored, err := EncryptBinaryMessageArmored(readTestFile("keyring_publicKey", false), plainData)
+
+	if err != nil {
+		t.Fatal("Expected no error when encrypting, got:", err)
+	}
+
+	assert.Exactly(t, true, crypto.IsPGPMessage(armored))
+
+	decrypted, err := DecryptBinaryMessageArmored(
+		readTestFile("keyring_privateKey", false),
+		testMailboxPassword, // Password defined in base_test
+		armored,
+	)
+
+	if err != nil {
+		t.Fatal("Expected no error when decrypting, got:", err)
+	}
+
+	assert.Exactly(t, plainData, decrypted)
+}