@Pete-S said in Sending Secure E-Mail?:

@scottalanmiller said in Sending Secure E-Mail?:

@Pete-S said in Sending Secure E-Mail?:

@scottalanmiller said in Sending Secure E-Mail?:

@Pete-S said in Sending Secure E-Mail?:

@scottalanmiller said in Sending Secure E-Mail?:

The system admin can always get the key out of your email and open whatever has been sent.

Completely incorrect as well. The public key can only be used for encryption, not decryption.

Oh, right, okay, having a "duh" moment. So you can send your public key via email, and ANYONE can send you an encrypted email, but ONLY to you. Because you have the private decryption key.

You are right, I follow now. That could work.

No problem. I'm not a crypto guy but we used PGP encrypted email for many years so I know the basic principles.

I've used it, but I was adding in the incorrect assumption that everything had to be done only on the sender's end. Which if you did that, encrypting with PGP and sending the key with it, anyone who intercepted would be able to read. But if the recipient can send the key too, then yeah, obviously that works great.

It's pretty easy to install and use nowadays, especially if you are just a couple of persons. You just install the add-on needed depending on your email client. Then you have to tell it what you want your passphrase to be and it will create your public and private key for you.

All you have to do then is email your public key to whomever you want to be able to receive secure emails from. And they'll do the same.

When you receive a secure email you have to enter your passphrase to read it.

Writing this I think the best way to use this for ordinary business use is to only send encrypted email when you are sending something sensitive, like passwords or stuff like that.

Problem with encrypted email (and also it's strength) is that you can't read it if you don't have your private key and passphrase. But it makes it complicated reading email on different devices and software unless you copy your private key everywhere and enter your passphrase on a number of insecure devices. Which defeats the security aspect of it.

So it works best on desktop clients and if you only encrypt when really needed, you are not much affected by the drawbacks. If you try to read an encrypted email on a devices that doesn't support it you'll just see an attachment that is just gibberish as my earlier post shows.

@scottalanmiller said in Sending Secure E-Mail?:

@Pete-S said in Sending Secure E-Mail?:

@scottalanmiller said in Sending Secure E-Mail?:

@Pete-S said in Sending Secure E-Mail?:

@scottalanmiller said in Sending Secure E-Mail?:

The system admin can always get the key out of your email and open whatever has been sent.

Completely incorrect as well. The public key can only be used for encryption, not decryption.

Oh, right, okay, having a "duh" moment. So you can send your public key via email, and ANYONE can send you an encrypted email, but ONLY to you. Because you have the private decryption key.

You are right, I follow now. That could work.

No problem. I'm not a crypto guy but we used PGP encrypted email for many years so I know the basic principles.

I've used it, but I was adding in the incorrect assumption that everything had to be done only on the sender's end. Which if you did that, encrypting with PGP and sending the key with it, anyone who intercepted would be able to read. But if the recipient can send the key too, then yeah, obviously that works great.

It's pretty easy to install and use nowadays, especially if you are just a couple of persons. You just install the add-on needed depending on your email client. Then you have to tell it what you want your passphrase to be and it will create your public and private key for you.

All you have to do then is email your public key to whomever you want to be able to receive secure emails from. And they'll do the same.

When you receive a secure email you have to enter your passphrase to read it.

@scottalanmiller said in Sending Secure E-Mail?:

@Pete-S said in Sending Secure E-Mail?:

@scottalanmiller said in Sending Secure E-Mail?:

The system admin can always get the key out of your email and open whatever has been sent.

Completely incorrect as well. The public key can only be used for encryption, not decryption.

Oh, right, okay, having a "duh" moment. So you can send your public key via email, and ANYONE can send you an encrypted email, but ONLY to you. Because you have the private decryption key.

You are right, I follow now. That could work.

No problem. I'm not a crypto guy but we used PGP encrypted email for many years so I know the basic principles.

This is what PGP encrypted email looks like. Like all email it's just plain text. Before this section is the usual email headers. So the "To:" and "From:" and "Subject:" is not encrypted but the email content itself is.

This is an OpenPGP/MIME encrypted message (RFC 4880 and 3156)
--xhndWJKlxj2H7EcRFNi37V5EBuMbJO6xj
Content-Type: application/pgp-encrypted
Content-Description: PGP/MIME version identification

Version: 1

--xhndWJKlxj2H7EcRFNi37V5EBuMbJO6xj
Content-Type: application/octet-stream; name="encrypted.asc"
Content-Description: OpenPGP encrypted message
Content-Disposition: inline; filename="encrypted.asc"

-----BEGIN PGP MESSAGE-----
Version: GnuPG v1.4.12 (GNU/Linux)

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=m2A7
-----END PGP MESSAGE-----

--xhndWJKlxj2H7EcRFNi37V5EBuMbJO6xj--

@scottalanmiller said in Sending Secure E-Mail?:

If they could exchange keys, of course, but there is a reason that we'd already pointed out that this didn't meet the criteria right away.

It's because you are thinking about symmetric encryption.

From wikipedia:

Symmetric encryption
"The overarching problem with symmetrical cryptography, or single-key cryptography, is that it requires a secret key to be communicated through trusted couriers, diplomatic bags, or any other secure communication channel. If two parties cannot establish a secure initial key exchange, they won't be able to communicate securely without the risk of messages being intercepted and decrypted by a third party who acquired the key during the initial key exchange."

Asymmetric encryption
Public-key cryptography uses a two-key system, consisting of the public and the private keys, where messages are encrypted with one key and decrypted with another. It depends on the selected cryptographic algorithm which key—public or private—is used for encrypting messages, and which for decrypting. For example, in RSA, the private key is used for decrypting messages, while in the Digital Signature Algorithm (DSA), the private key is used for encrypting them. The public key can be sent over non-secure channels or shared in public; the private key is only available to its owner.

@scottalanmiller said in Sending Secure E-Mail?:

It ends up doing nothing more than TLS already does, but with a lot more manual work.

Completely wrong as well. TLS is just transport encryption. When it's not in transport, it's not encrypted.

@scottalanmiller said in Sending Secure E-Mail?:

The system admin can always get the key out of your email and open whatever has been sent.

Completely incorrect as well. The public key can only be used for encryption, not decryption.

@scottalanmiller said in Sending Secure E-Mail?:

you have to exchange keys outside of email

Sorry Scott, but that is completely incorrect. The public key is public.

These are some of the software and services that support encrypted mail with GPG/PGP inside the mail client.
https://www.openpgp.org/software/

It's an open standard: https://tools.ietf.org/html/rfc4880

@JasGot said in Sending Secure E-Mail?:

@JaredBusch Thanks. Not much more to it beyond what I thought. I was hoping someone would know of a solution that could work.

GPG/PGP works exactly like you want.

It's asymmetric encryption. If you wanted to send a secure email to me, you need my public key. Since it's public I can send it to you in an email and I could post it online. Whatever.

When you send a secure email to me you encrypt it with my public key. To be able to view the email I need two things - my private key and my passphrase. None of those are available to anyone else.

The email is stored on the email server as it was sent - fully encrypted. And so is it on my computer. So a sysadmin with access to the email server can't do anything. A sysadmin with full admin rights on my computer could get my private key. But not the passphrase. So can't do anything with the encrypted email.

Emails can also be signed. Which means that using your public key, I can verify that the email you sent me actually came from you and nobody else.

This is exactly what happens when you download software from repositories like ubuntu, debian etc. The package manager need the public key of the repository to verify that the packages are from there and not some shady individual.