Write and Protect a Message

This page shows how to write an email in GpgFrontend and how to protect it.

• Signing proves the message came from you and was not changed on the way.
• Encrypting hides the message so only the people you choose can read it.

You can do one, the other, or both. Everything happens on your own computer.

On a Mac, press Cmd where this page says Ctrl, and Option where it says Alt.

Start a New Message

1. Click File > Workspace > Mail Editor.
2. A new tab opens with an empty message.

Each message is an .eml file. You can save it with File > Save File or File > Save As…, like any other file.

Fill In the Header Fields

The header fields sit at the top of the message:

• From: who the message is from. This is you.
• To: who the message is for.
• Subject: what the message is about.

To add more people:

1. Click Cc/Bcc at the end of the To: row (or press Ctrl+Shift+C).
2. Two more rows appear: Cc: and Bcc:.

What these mean:

• Cc (carbon copy) sends a copy to someone. Everyone can see who was in Cc.
• Bcc (blind carbon copy) sends a copy in secret. The other people do not see this name.

To add several people in one field, put a semicolon (;) between the addresses. For example: [email protected]; [email protected].

Each address can be written as [email protected] or as Alice <[email protected]>.

Address Suggestions

As you type an address, GpgFrontend suggests matching addresses:

• In From:, it suggests your mail accounts first, then the addresses on your own private keys.
• In To:, Cc: and Bcc:, it suggests the addresses on the keys in your key database.

About Bcc

Names in Bcc: are never written into the message itself. If they were, every reader could see who got a secret copy.

GpgFrontend still uses them in two ways:

• When you encrypt, it can use them to pick the keys to encrypt to.
• When you send, it gives them to your mail server, so they still get the message.

They are not saved in the .eml file.

New in v2.2.3

The header fields are now part of the message tab. The old pop-up window that asked for From, To and Subject is gone.

Write the Body

Click in the large area below the header fields and type your message. It shows Write your message here. until you start typing.

Attach Files

1. Click Attach File… (or press Ctrl+Shift+A).
2. Pick one or more files and confirm.

You can also drag files from your computer and drop them onto the message.

Each file can be up to 48 MiB. Folders cannot be attached. If a file is refused, a window tells you which one and why.

Your attachments are listed under the message. To learn more about the list, see Work With Attachments.

Reply, Reply All and Forward

When you open a message you received, the action row shows three buttons:

• Reply (Ctrl+R): write back to the sender.
• Reply All (Ctrl+Shift+R): write back to the sender and everyone else who was addressed. People in Bcc are not included.
• Forward (Ctrl+L): pass the message on to someone else, with its attachments.

Each one opens a new tab with a new message. The original message is not changed.

On a message you are still writing, these buttons are not on the row. You find Send… and Attach File… there instead. Other actions are under More.

Message and Raw Source

Above the body you can switch between two views:

• Message (Alt+1): the normal view, with header fields, body and attachments.
• Raw Source (Alt+2): the full message as plain text, exactly as it is stored in the file.

The raw source is read-only at first. To change it by hand:

1. Switch to Raw Source.
2. Click Edit Raw Source.
3. Make your changes. What you type here is the message itself.
4. Click Stop Editing when you are done.

Most people never need the raw source. It is there for checking or fixing a message by hand.

Sign or Encrypt the Message

First pick your keys in the Key Toolbox on the right:

• To sign: check your own private key.
• To encrypt: check the public key of each person who should read the message. Check your own key too if you want to read it later.

Then use the Security menu:

1. Find the status button at the right end of the action row. On a new message it says Not signed or encrypted.
2. Click it. A menu opens.
3. Choose one:
   • Sign…: sign the message.
   • Encrypt…: encrypt the message.
   • Encrypt and Sign…: do both at once. This is the best choice for a private message.

The result shows in the Status Panel. The status button changes to tell you what the message is now, for example Encrypted.

You can also use the Sign and Encrypt buttons on the main toolbar. They do the same thing. Encrypt & Sign is in the Encrypt button’s list: right-click the button to find it.

What the Security Menu Offers

The menu changes with the message. This is what you see:

The message is…	The menu offers
Not signed or encrypted	Sign…, Encrypt…, Encrypt and Sign…
Signed	Verify Signature, Signature Details…, Sign Again With Another Key…, Remove Signature…
Encrypted	Decrypt, Decrypt and Verify, Encryption Details…
Encrypted and signed	Decrypt and Verify, Decrypt, Details…, Remove Signature…
Broken	What Is Wrong With This Message?, Try to Verify Anyway, Try to Decrypt Anyway

“Broken” means the message says it uses OpenPGP, but it is not built the right way. To learn how to check a message you received, see Verify and Inspect a Message.

Signed and Encrypted Messages Are Locked

Once a message is signed or encrypted, you cannot edit it. A notice above the body tells you why:

• Signed: a change under a signature would look like a forgery. To edit, first remove the signature with Remove Signature… in the Security menu.
• Encrypted: decrypt it first.
• Encrypted and signed: decrypt it, then remove the signature.

If you try to change a signed message anyway, GpgFrontend asks: Remove the signature and make it an ordinary message? Click Yes to remove it, or Cancel to keep it.

Removing a signature cannot be undone. The text of the message is kept as it is.

Lock a Message Yourself

You can also lock a message you received, so nobody changes it by accident:

1. Click More.
2. Click Read-only.

A Read-only label appears. Reply and Forward still work, and they make new messages. To unlock, click More > Read-only again.

Send or Save the Message

You have two choices:

• Send it from GpgFrontend. Click Send… (or press Ctrl+Enter). You need a mail account for this. See Mail Accounts and Sending.
• Send it with another email app. Save the message as an .eml file with File > Save As…. Then open or import that file in your usual email app and send it from there.

Before the file is saved, GpgFrontend takes a last look at the message. If something looks risky, it shows a Check before exporting window. See Check Before Exporting.

Understand the Results

After you sign, encrypt, verify or decrypt, the Status Panel shows the result as a set of cards:

• E-Mail: the message headers: From, To, Subject, CC, BCC and Date.
• OpenPGP: two technical values about the signature:
  • Digest of Signed MIME Entity (SHA-256): a fingerprint of the exact part of the message that the signature covers. If two copies show the same value, the signed part is the same in both.
  • Declared Signature Hash (micalg): the hash method the message says its signature uses. This is only what the message claims.
• Attachments: each file in the message. It also says when a file is an OpenPGP key, or when it is not covered by the signature.
• Recipient Check: for encrypted mail, whether each person in the headers can really read it. A warning here means someone was addressed but not encrypted to, so they cannot open it.
• Encryption Recipient: who each copy was encrypted to, shown as the key’s name and Key ID.

Tips and Troubleshooting

• Send… is grayed out. Hover over it. It tells you what is missing, for example a subject or a recipient.
• A signature shows as bad, but the text looks fine. A signature covers the exact bytes of the message. Some programs change line endings or re-encode a message when they save or forward it. When you can, save the original .eml file instead of a copy.
• You cannot decrypt a message. Check that the matching private key is in the key database you are using right now.
• The reader cannot open your message. Make sure their email app supports PGP/MIME. Apps that only know older “inline PGP” may not open it.
• Keep private keys safe. Never upload them to an email provider.

Good to Know (Technical Details)

You can skip this section.

• GpgFrontend follows the OpenPGP standards (RFC 4880 and RFC 3156). The messages work with Thunderbird and other OpenPGP email apps.
• It makes PGP/MIME messages, not inline PGP. A signed message has its signature in a separate part. An encrypted message is wrapped as one encrypted part. This keeps the body, attachments and formatting intact.
• .eml files work almost everywhere. You can always move a message to or from another email app.