As far as I know, there's only one app out there that meets all of your criteria. All of your requirements (reproduced below) describe pyrite, though it can do more.
"text area where I could paste text then encrypt or decrypt"
"should be able to sign and check signatures"
"Produces ASCII" (pyrite can do both)
"Open source" (GPLv3)
"Runs on Linux" (...
There is a bunch of open source OpenPGP key server implementations.
The OpenPGP Public Key Server (PKS) based on a thesis of Mark Horrowitz is a rather old implementation, but still under active development.
SKS keyserver is probably the one running most key servers at this time. There are ready-to-use packages for eg. Ubuntu.
Hockeypuck is another very ...
Your scenario is a little sparse on details but I would like to suggest that you are probably barking up the wrong tree altogether.
If you are the only author and consumer of text data, it is unlikely that a web browser, hosting provider and text areas is the best way to manage that text data. There are in fact much better ways. Here are some possibilities:
GnuPG or GNU Privacy Guard is available for all the main desktop OSs and even Android there is a Portable version for use on windows machines without installation: Either by downloading from here installing then and running mkportable.exe or as gpg4usb.
Keep in mind that if you loose a USB key with your keys on you have to regard them as compromised.
There are two software stacks implementing OpenPGP with Outlook 2013 Plugins:
The Gnu Privacy Guard GnuPG, which is free software. Gpg4win bundles the software for Windows, and adds some GUI clients and an Outlook plugin:
Gpg4win runs on Windows XP, Vista, 7 and 8. Both 32 and 64bit systems are supported.
The Outlook plugin GpgOL is compatible with ...
I'm not aware of any readily-build software that is able to do this; it might be possible to program such an application using libraries like Bouncy Castle (Java, C#) or the OpenPGP package for Go.
But I can help you with a workaround: GnuPG allows to use a seperate "home directory", and thus also keyring. Doing something like
Mymail-Crypt for Gmail™
Integrates with the GMail interface
You can decrypt e-mails with a "decrypt" button
Works with Windows 7
"This project is no way affiliated with Google™."
The project is powered by OpenPGP.js. OpenPGP.js aims to fully implement the RFC 4880 OpenPGP standard. This project is still a work in progress, but supports a ...
Difference between AES-256 and OpenPGP
First, I want to clarify that AES-256 and OpenPGP are not mutually exclusive. It's simpler to look at OpenPGP as wrapper for data encrypted with AES-256 symmetric cipher. OpenPGP format specification also tells how to store encryption parameters in the file including the cipher AES-256, Hash algorithm, salt, iterations ...
pyrite (already cited) and gpg4usb (https://www.gnupg.org) have the requested features: direct copy/paste and processing of text (on a text-editor like window without the need to actually saving the plain and encrypted messages) + ASCII output + open source + runs on Linux + uses ~/.gnupg GPG key info (both let you choose which key to use).
Here is the ...
If the missing ASCII-armored output is your main objective regarding Seahorse, it can be configured to produce ASCII-armored output. The configuration option is not available in the GUI, so you need to change seahorse-settings in gconf.
There is a bunch of configuration options available, the setting of interest is
you can use Pandor:
it's Free for personal use
you don't have to handle keys exchange with recipients, they recieve automatically an email with an account
uses OpenPGP for mail encryption.
Available in chrome Web Store and works with gmail
you don't have to copy/paste you text somewhere to encrypt/decrypt.This is done automatilly once connected to your ...
You can use End-To-End:
open source and free
developed by Google
released on June 3rd, 2014
supports RFC 4880 (OpenPGP Message Format) and RFC 6637 (Elliptic Curve Cryptography (ECC) in OpenPGP)
beware it is in beta and may have security issues
not available in the Chrome Web Store yet
Gajim (FLOSS; available for GNU/Linux, FreeBSD, Microsoft Windows) supports OpenPGP by default.
Your own key:
Open the accounts menu (Ctrl+Shift+a).
Select an account.
Go to the tab about personal information.
Under the "OpenPGP" section, press the button for selecting a key.
Select your key from the list.
Now when you go online with this account, you ...