9

Say I have an email and I want to send it to someone else. I encrypt it with his public key. This ensures that only he can read my message. Does this also means that I won't be able to read it? If so, how will I know what I have sent?

4
  • 1
    I believe generally your mail client would encrypt a copy for yourself (using your public key), so that you can still decrypt later.
    – Xaqq
    May 9, 2015 at 0:49
  • And store it locally? And the only place where from I could see my messages is in my pc, unless I always send a copy to mey self so that I could also decrypt it too?
    – jaxkodex
    May 9, 2015 at 0:52
  • Yep, actually I Just sended the encrypted text via e-mail, i ment "send it to me" assuming i would use a plug in or something
    – jaxkodex
    May 9, 2015 at 0:59
  • be carefull, headers are not encrypted, including email's title.
    – Aif
    May 9, 2015 at 21:49

3 Answers 3

14

It's perfectly true. Encrypting an e-mail with someone public key, you get as output a ciphered text that you cannot decrypt yourself, this is the point of asymetric cryptography after all.

There are many methods to keep the original text.

  • keep it as clear-text
  • encrypt it with your own public key (to keep confidentiality)
4

You should play with GPG, your question will answer itself real quick. I recommend a GPG tool called Mailvelope which works with most web-based emails (gmail, hotmail, yahoo, etc).

You can encrypt a message for multiple recipients, and as @Xaqq said, most clients will include the sender in the recipients list for exactly the reason you state. But if you don't, then no, you will not be able to read your own send messages. I've certainly made that mistake before.

1
  • Already did and I could not decrypt my message :), thats why I wanted to confirm my supicions
    – jaxkodex
    May 9, 2015 at 0:56
4

Yes, basically you're right: if you (or your mail client) do not specify yourself as somebody that should be able to decrypt the message, only the recipient will be able to read the message.

Multiple encryption keys are possible

But: who can read your data depends on whom it is encrypted for. For example, most mail clients will encrypt for everybody in the "To:" and "CC:" fields (while "BCC:" recipients are treated special to not reveal them), and additionally the sender (so he can read it on his own again).

Be aware encrypting to multiple users does not increase the message size linearly with the number of recipients: OpenPGP uses a hybrid encryption schema, where only the "session key" used for symmetric encryption must be encrypted (this time with public-key-cryptography) for everybody who shall be able to decrypt the message.

If your mail client does not encrypt to yourself

When your mail client (or GnuPG plugin) does not allow to configure this, chances are good that GnuPG's default configuration stays in place. There is an option --encrypt-to, which allows providing an additional recipient. From man gpg:

--encrypt-to name

Same as --recipient but this one is intended for use in the options file and may be used with your own user-id as an "encrypt-to-self". These keys are only used when there are other recipients given either by use of --recipient or by the asked user id. No trust checking is performed for these user ids and even disabled keys can be used.

This option can be also set in GnuPG's configuration file ~/.gnupg/gpg.conf, where the -- must be omitted. name can be a key ID or user ID; I'd recommend going for the full fingerprint or at least long key ID to precisely describe your key.

An example configuration directive, which would also add myself as recipient, would be

encrypt-to 0D69E11F12BDBA077B3726AB4E1F799AA4FF2279

--encrypt-to could be also used if your mail client allows adding parameters which are passed to gpg.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.