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The Women’s March and other demonstrations and protests taking place nationwide tomorrow will also be monitored by a large contingent of local and federal law-enforcement officials. In an ideal situation, peaceful, lawful protest would not get anyone into trouble — but this is not the society we live in, and even nonviolent protesters may find themselves swept up in mass arrests or have their privacy or safety otherwise compromised by heavy-handed policing or broad surveillance mechanisms.

Luckily, there are a handful of easy ways to ensure that you’re not giving up private information — like messages to fellow activists, or your location — while also lawfully demonstrating. If you’re anticipating getting into what Representative John Lewis has described as “good trouble” at the protest, here are some things you should do.

Leave your phone at home

Seriously. Do not bring your phone with you. Make a plan to meet up with friends, and come up with a meet-up location in case you get separated instead. Along with personally identifiable information, like text messages and social-media accounts, which might incriminate you or others, your phone’s location-services function can track your movements and whereabouts. Carrying your phone with you is literally carrying a large record of who you are, what you’re up to, and where you’ve been. If you don’t want authorities to have access to that record, don’t even create it. Leave your phone at home.

Encrypt your phone

Okay … so you decided not to listen and you brought your phone to the protest. Now you need to encrypt it with a passcode. On an Android, go to Settings > Security > “Encrypt phone” and follow the directions. If you have an iPhone, go to the Settings app, select “Touch ID & Passcode,” and create a passcode. Make sure it’s longer than the default four digits. Even bumping your passcode length up to six digits increases its complexity exponentially — and throwing letters and other characters into the mix makes it almost impossible to crack. Similarly, if the programs on your phone support it, activate passwords on a per-app basis.

If you back up your phone, make sure that the backup is encrypted as well. (Apple has instructions here.) And back it up locally — with an iPhone, through iTunes. If you back up your phone to the cloud, law enforcement can obtain the archived contents of your phone from the cloud provider without your cooperation.

Turn off Touch ID

The legal question of whether police can compel you to unlock your phone via biometric authentication — i.e., your fingerprint — is still very much up in the air, but the odds are not in your favor. And if you get arrested and fingerprinted, law enforcement might not even need your assistance to do so. So turn off this functionality (on an iPhone: Settings > “TouchID and Passcode”), and stick to unlocking via keyboard input. That being said, a court ruled as recently as last month that police could compel someone to give up their passcode, so it bears repeating: Do not bring your phone.

Use an encrypted messaging app

If you do need to text people, use an app that provides end-to-end encryption by default. (End-to-end encryption means that your messages will be encoded on your device and decoded on your recipient’s device, preventing eavesdroppers from easy interception.) The best option is Signal, but if for some reason that’s not available WhatsApp also offers E2EE (just make sure that you don’t connect it to your Facebook account). These apps don’t require a user account, but do require a working phone number. If you need a burner, you can get a free VoIP number from services like Google Voice.

All of this is dependent on cellular networks working, though. Given the high concentration of users, there’s a decent probability that networks will be congested, slowing to a crawl. In that case, you and your comrades might want to use a mesh-networking messaging app like FireChat, which uses other phones as nodes to transmit messages without an internet connection (the messages are encrypted).

Don’t use your usual social-media account

This is another “no duh,” but if you’re going to be posting photos or footage of disruptive or unlawful behavior, don’t do it on your regular Facebook or Twitter account. There’s also a case to be made that posting photographs on Facebook, Twitter, or Instagram just serves to widen the surveillance net being cast by authorities, who have even more data to pore over and comb through. When in doubt, remember that not even the most sophisticated facial-recognition technology can distinguish the backs of peoples’ heads.

If you get arrested, don’t post to Facebook till you’ve talked to a lawyer

If you do get arrested, think cautiously before tweeting or Facebooking about it. The first thing you want to do is contact a lawyer. It’s worth having that phone number memorized or written down somewhere. The National Lawyers Guild’s D.C. hotline is 202-670-6866.

Did I mention DON'T TALK TO THE POLICE? The best most saintly fair played-by-Jimmy-Stewart cop is still not your friend. — HeartyStewHat (@Popehat) January 20, 2017

Anyway, above all, don’t be a frickin’ idiot! Stay safe!