Free and Open Source Software (FOSS) is software that is usually no cost and has a non-proprietary code available for the public to review.
Typically commercial software companies do not reveal their code because they view their software as intellectual property and drive up their competition. Downloading commercial software also assumes trust and goodwill that the company will not add a "backdoor" or a way for that company to access your private information on your device.
FOSS counters this by making the code open for the public to review & analyze. Technical knowledge of coding language is needed to review but there are large enough communities of FOSS advocates, cypherpunks, hackers, and ethical developers online to catch suspicious code.
FOSS is the gold standard for digital security, and the recommendations below reflect these principles.
Signal1 is a private-messaging FOSS app for mobile and desktop devices. It employs end-to-end ecryption and is used by governments, journalist, and organizers alike to protect their communication. Signal has been transparent about government requests for their data2. Sometimes tech companies get gag orders, which means the company cannot tell the public that the government has requested their data. In these instances Signal is also protected because they have proven to the courts3 that they only collect 2 types of data: timestamps of accounts created, and the date each account has last connected to Signal.
Signal's additional digital-security-rock-star features include verifying a safety number4, setting disappearing messages, and having usernames to remain anonymous in chats. While you may remain anonymous in chats, Signal still collects your phone number.
For a step-by-step guide to set up your Signal account with a second number, please follow The Freedom of Press Foundation's, “So you want a second Signal account5.” An important note is that Signal is set up for privacy, not true anonymity. For example, whether its through Google Voice, a burner app, or traditional phone company, your phone service provider (and potentionally a government who is ordering them to hand over the data) can often tie your phone number to you.
KeePassXC8 is an offline password manager that is FOSS.
Commercial, cloud-based passwords managers (e.g. ones that are accessible via browser) are susceptible to cyber attacks9.
With any kind of password manager, online or offline, it is crucial that you remember your master password.
Keep a written copy of your master password in a secure inconspicuous location, perhaps written on a phone bill or a sticky note on your rental lease.
JUST REMEMBER WHERE YOU LEAVE IT! This cannot be retrieved if lost.
A downside to an offline password manager is that you are unable to access on your mobile device.
While not a solution, you may also want to consider downloading a portable version of KeePassXC to a USB drive. This will allow you to open the password manager via your USB drive from whichever device you are plugged into.