If you received email from me in the early 2000s, it would have arrived with an attachment I routinely added to my messages. The attachment was my digital signature, the output of an algorithm that combined my message with the private half of my cryptographic key pair. If you had acquired my public key as part of a prior communication, and if your email client supported the protocol, you were assured that the message had been “signed” by me. Since those two conditions rarely applied, though, you were more likely to be puzzled or annoyed.
Why did I do this? As I look back, I think it had a lot to do with my experience in the early blogosphere. Back then blogs didn’t support comments. To comment on something you wrote, I’d write a blog post referring to your post. You could reply in the same way. The conversational thread didn’t exist in any one place, but in practice links wove the discussion together well enough. And because all our writing appeared on our own blogs, we owned our words. Discourse was typically much more civil than in discussion forums, or in the comment areas that blogs later evolved.
I liked the idea that my digital output was bound in some way to my identity. In the case of blogging, that identity was associated with a website that I controlled. Why not extend that idea to email? In that case, my identity was associated with a key pair, the private half of which I controlled. Signing messages was a way to say: “I own and stand behind these words.” And to say: “You should distrust a message ‘from’ me that isn’t properly signed.”
When I abandoned my digital signature experiment I chalked it up to a failure of technology adoption. It was, I thought, a good idea that never took off because people didn’t understand why it was a good idea, or because popular software didn’t make it accessible enough.
Now a hugely popular email program, Gmail, is about to make the idea more accessible than it’s ever been. Google is preparing a Chrome extension called End-to-End for encrypting (and signing) email. I should rejoice! But Yaron Goland thinks otherwise. He argues here that routinely binding our identities to our messages is a really bad idea.
Imagine, for a moment, what your world would look like if every time you had a conversation with someone a permanent record was made of the conversation. The record would be fully authenticated and suitable for use in the court of public opinion and/or law.
In this world our everyday lives, our conversations, our exchanges, with anyone about anything become little permanent records that follow us around forever.
This is exactly the world we create with technologies like S/MIME and PGP Mail. Or, more generally, the world we create when we use digital signatures. A digital signature is intended to be an authenticator, a way for someone other than us to prove that we did/said something. When we use digital signatures for momentous things that should be on the public record, like mortgage documents perhaps, then they serve a good purpose. But with PGP Mail we suddenly sign… well… everything. It’s like having a notary public walking behind you all day long stamping every statement, note, mail, etc. as provably and irrevocably yours.
I don’t think we want such records to exist. I think we want a much more ephemeral world where the bulk of what we do just quietly vanishes into the ether leaving as little of a trail as possible. The open source experiment I’ve spent the last year or so working on (and why I haven’t been blogging much, I’ve been insanely busy) is called Thali and we are trying to build that ephemeral world.
Yaron calls the dystopian vision he conjures “a world without hearsay” and Thali rejects it. When you communicate with a Thali peer, you and the peer strongly authenticate one another. But the data you exchange bears no trace of those identities. At least not by default. Thali applications will, of course, often need to add markers of identity to the documents they exchange. But the Thali system won’t do that automatically.
If email were exchanged directly among peers, rather than through relays, then I might never have felt the need to bind identity to individual messages. Since email travels through relays, though, I would still like to assure you that email “from” me really is from me, as well as protecting it from the prying eyes of intermediaries and servers. But I find Yaron’s argument persuasive. The potential harm to me may outweigh the benefit to you.
 End-to-End isn’t, by the way, a Gmail-only thing. You can use it in any text entry field in the Chrome browser to compose a signed/encrypted message. I don’t use Gmail but was able to use End-to-End to send a protected message from Outlook.com. That entails copying and pasting though, which presumably won’t be necessary if End-to-End is integrated into Gmail.
 Signing and encryption aren’t necessarily joined at the hip. Depending on how the technologies are implemented, it may be possible to sign without encrypting, encrypt without signing, or sign and encrypt. I tried the End-to-End extension and found that it doesn’t do bare signatures but does encrypt with or without signatures. So you could use it to protect messages without binding your identity to them.