All I know is that some form of PGP/GPG can be used on iOS, as I get emails from people that use that platform. A quick search shows iPGMail and oPenGP. Not free, opensource, but... PD
I get PGP emails from people using Macs (Apple-Mail with GnuPG/MacGPG2 v2.0.19 (Darwin) encrypted content). Enigmail in Thunderbird deals with them fine, but K-9 Mail with AGP (OpenPGP for Android) has trouble opening the messages. Anyone else have this issue? Did you find a solution? What are the recommended OpenPGP apps for iPhone/iPad? (just so I can pass on the info)
I had some problems too when trying to decrypt emails sent with S/MIME. Without it and with emails as plain text (not HTML), it's been working ok. Try to disable (in Thunderbird) S/MIME before sending an email to some of your own accounts and decrypt it with K9. It should work. I could not find how to disable S/MIME in Apple Mail + GPGMail, so to decrypt them you can download the attached file and open it with APG. That's the only way I found to decrypt them. It's a little bit uncomfortable, but at least you can read the encrypted email. I hope I have made myself clear (english is not my native language )
I think I have found the solution. Check this link: http://support.gpgtools.org/kb/faq-gpgmail/gpgmail-2-hidden-settings So, this is the way I fixed it: 1) Close Apple Mail 2) Open a new terminal and write: $ killall -9 gpg-agent $ defaults write org.gpgtools.gpgmail UseOpenPGPInlineToSend -bool YES 3) Open again Apple Mail and try sending an encrypted mail using OpenPGP. You should be able to open it with K9 in Android. It worked for me, but keep this in mind: If yoy want to switch back to OpenPGP / MIME standard: 1) Close Apple Mail 2) In a terminal: $ killall -9 gpg-agent $ defaults write org.gpgtools.gpgmail UseOpenPGPInlineToSend -bool NO I hope it helps.