This is a program for the Tandy / Radio-Shack TRS-80 Color Computer to perform RSA key generation, encryption, and decryption. The code is all written in 6809 assembly. It will operate with up to 2048 bit keys.

It should work on any CoCo with at least 32kb of memory. 16k CoCos should work for smaller keysizes.

VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux. Brought to you by IDRIX (https://www.idrix.fr) and based on TrueCrypt 7.1a.
VeraCrypt main features:

Creates a virtual encrypted disk within a file and mounts it as a real disk.
Encrypts an entire partition or storage device such as USB flash drive or hard drive.
Encrypts a partition or drive where Windows is installed (pre-boot authentication).
Encryption is automatic, real-time(on-the-fly) and transparent.
Parallelization and pipelining allow data to be read and written as fast as if the drive was not encrypted.
Encryption can be hardware-accelerated on modern processors.
Provides plausible deniability, in case an adversary forces you to reveal the password: Hidden volume (steganography) and hidden operating system.
More information about the features of VeraCrypt may be found in the documentation

Mailvelope is available as a web browser extension for Chrome / Chromium and Firefox. It uses OpenPGP.js to add encryption and digital signature capability to any webmail service.

Enigmail is a seamlessly integrated security add-on for Mozilla Thunderbird. It allows you to use OpenPGP to encrypt and digitally sign your emails and to decrypt and verify messages you receive.

Enigmail is free software. It can be freely used, modified and distributed under the terms of the Mozilla Public License.

privacytools.io provides knowledge and tools to protect your privacy against global mass surveillance.

if you want to use LUKS In-Place Conversion Tool, the notes below on converting a shipped-with-Ubuntu Dell XPS 13 Developer Edition (2015 Intel Broadwell model) may help you. There were a couple of small learnings to be had...

Finally Let’s Encrypt went public with their open source, easy to use, SSL certification solution (Available for everybody, starting on the 3rd of December).
And yes, it’s free! As I’m writing this, Let’s Encrypt is still beta status, but working well in a productive environment. Check out their site to understand how it works.

We've been discussing some of Jelly Bean's new security features, but this post will take a few steps back and focus on an older one that has been available since Honeycomb (3.0), announced in the beginning of the now distant 2011: disk encryption. We'll glance over the implementation, discuss how passwords are managed and introduce a simple tool that lets you change the password from the comfort of Android's UI.

If you're worried that you're not paranoid enough about your communications security and want to improve your OpSec, it is actually fairly easy to go "full-Sn*wden" with hardware storage of your PGP secret keys. The Yubico Yubikey-Neo and Neo-N USB tokens are a neat (and cheap) way to keep your keys locked in a hardware device rather than stored as a file on your harddrive. The hardware tokens are compatible with the OpenPGP card protocol, which recent versions of gnupg support out-of-the-box. All of the public-key cryptography happens inside the tamper-proof device, so your secret key is never decrypted in the memory nor stored on disk of your machine.

It's possible to publish your public PGP key in the DNS. There is a really good guide at http://www.gushi.org/make-dns-cert/HOWTO.html which explains the three different methods in detail. It's really simple though, so I'll explain how I did it. I'm going to replace my email address with a fake address to avoid feeding the spambots.

DiskCryptor is an open encryption solution that offers encryption of all disk partitions, including the system partition. The fact of openess goes in sharp contrast with the current situation, where most of the software with comparable functionality is completely proprietary, which makes it unacceptable to use for protection of confidential data.

The new UI for adding users lacks the "encrypted home diretcory" option.

Whisper Systems provides security and management solutions that transform consumer phones and tablets into enterprise-ready devices.

KeePassDroid is a port of the KeePass Password safe for the Android platfor

There's no public key encryption for Android yet, but that's an important feature for many of us. APG tries to fill that void, with new features quickly being added. Hopefully APG will grow into a fully functional OpenGPG implementation of GPG or PGP calibre.