Anonymity is the absence of Identification (or Onymity), it is when individuals are indistinguishable from each other, they all look the same.
In short, Anonymity means you are not identified. In this example, Someone hid their identity, and is talking to Alice. That someone is anonymous until Jack can figure out who that person is.
Anonymity is extremely fragile when that Someone is not implementing strict OPSEC practices, relating to:
Using the correct Technology: (What is that Someone using, to protect their Anonymity ? (A mask, a Coat, a mask / the Tor network, i2p, etc))
Using the correct Behavior: (By that Someone's actions, they are not revealing who they are. (They are not saying they are Walter Hartwell White living at XYZ)
DISCLAIMER: That Someone remains Anonymous UNTIL THEY MAKE ONE OPSEC MISTAKE !
Keep in mind that maintaining Anonymity is a much stricter practice than that of maintaining Privacy, as you will see, more threat vectors come into the picture.
The strength of your Anonymity is measured by the odds of finding you amongst a group of people.
- Anonymity
let's say your Anonymity is Perfect and you are simply "one human being in the world", the adversary currently has a chance of 1 out of 8 billion to guess that it is you. He'd do better to try and play the lottery than to try and guess that it's you.
Now let's say the adversary knows that you live in France what are the odds now ?
If the adversary knows you live in France, the odds have been significantly reduced from 1 out of 8 billion to 1 out of 65 million, but still that's not enough to accurately pinpoint you, the probability of the adversary figuring out who you are is still very low.
- Pseudonymity
But now let's say that the adversary knows more than that, let's suppose that the adversary knows that you have a masters in cybersecurity, and that you work a general IT job in France, for a software company. Now the odds have shrinked further, especially if the adversary is able to combine multiple sources of data to try and profile you.
Let's say you are trying to chat on SimpleX while the adversary is in the chat with you, and he sees that you have a gorillaz profile picture, call yourself Nihilist, and talk about Opsec all the time. If the adversary is good at profiling you over time, he could have already shrinked down the odds to 1 out of 10 thousand people. Here we're talking about a drastically reduced anonymity, which we can consider to be pseudonymity. but that is still not enough to know who you are IRL.
- Onymity
But you need to be aware that even the tiniest opsec mistake can reduce the odds of your anonymity to 1 out of 1, where you are effectively deanonymized. For instance let's say you are in this SimpleX chatroom , and let's say you are sending a picture of your own limited edition MoneroChan fumo plushie:
Now the thing is, there are only 100 of those plushies out there, if the adversary is the seller of those monerochan plushies, your anonymity odds has been reduced to 1 out of 100, that's because he knows to whom he sent those 100 plushies, meaning he now only has a group of 100 people to guess who you are from. But upon closer exception it is worse than you may think:
If you look closer at the image the "Certificate of authenticity" says that it is the 41st plushie amongst the 100 that exist. Therefore if the adversary is the plushie seller, your anonymity odds have been reduced 1 out of 1 as he knows to whom he sent the 41st plushie. Meaning that you just deanonymized yourself for that particular adversary.
You get the idea, if you want to remain Anonymous, you need to always ask yourself "how many people could send that?", if you were to send that picture i sent above, you'd realize that this is a bad idea. The same concept applies as if you were to say what is your real IRL name, your phone number, your home address, your home public IP address, etc. Do not give bullets to an adversary, as he will use everything you give him to shoot you.
The least info you send about yourself, what you like, what you dislike, where you live, where you work, what's your past, the better, as otherwise it will be exponentially easier for an adversary to narrow down the possibilities of who you could be, amongst a given group of people.
The first the and foremost enemy of Anonymity is Surveillance of any kind. Privacy is a REQUIREMENT if you want Anonymity.
Example:
Jack is surveilling Bob 24/7. He sees that Bob purchases a mask and a coat, He sees that Bob wears the mask to then go outside to do something sketchy.
Conclusion:
Because Bob did not have Privacy from Jack in the first place, Bob cannot have Anonymity either.
Surveillance CANNOT be tolerated when you want Anonymity. So before you try to learn to be anonymous online, learn why and how to get Privacy online here.
The other major enemy of Anonymity is Know Your Customer (KYC) Procedures, these are ways for services to force their customers to identify themselves, wether they like it or not.
Example:
Jack owns an online service (such as a centralised crypto exchange), he accumulated a large userbase over the years, over 1000 active users. The government where Jack operates is ramping up their financial regulations on businesses, and now Jack is being forced to identify all of it's users using standard KYC procedures
Bob (an user on the website) that was anonymous up until that point, is now forced to do the following if he wants to keep using the platform:
1) state his real life name
2) his date of birth
3) his home address
4) send photos of his identity card
5) send photos of his face (facial left, front and right sides)
Conclusion:
Jack is either forced to identify his users or go out of business
Bob is either forced to identify himself or stop using the service
All of it because the government intends to destroy Bob's right to remain Anonymous online.
But the root cause of surveillance and KYC procedures, is that every centralised entity (any public or private business) will be eventually forced to comply to their government's requests, at the expense of their users.
There are only 2 possible long-term outcomes for Centralisation:
Act as a governmental proxy to enforce regulations/agendas, at the expense of users' rights
Or be forced out of business altogether.
To be able to achieve Anonymity, you need Privacy, and at least some level of Decentralisation (in the case of anonymization networks like Tor for instance), as we will see in our next tutorials.
In a way, Anonymity is an improvement over Privacy. In the sense that Privacy is about being about to seclude yourself or information about yourself. Anonymity is the logical next step to Privacy, Where you not only just conceal what your actions are, but also who you are.
Depending on the context, especially if you are living in a dictatorship, Anonymity is vital for you to act freely, out of the grasp of adversaries.
As we have discussed previously, for a government's laws to be respected, they need to be enforced.
And for the laws to be enforced, governments need:
To know what happened (lack of 
Privacy, using Surveillance )
To know who did it (lack of 
Anonymity, using KYC procedures )
Governmental control as a concept itself rests upon these fundamental 2 pillars, the detriment of the individual's Privacy, and Anonymity.
In order to regain the control you lost to dictatorships, you first need Privacy, and then you need Anonymity.
Most governments want to control the public opinion through opression and censorship, Journalism is one of the most demanding sectors in terms of Anonymity, especially in authoritarian/dictatorship governments where censorship is omnipresent, for them, very sadly, Anonymity is the difference-maker between life and death in those areas of the world.
For instance, the Freedom of the Press index is a great indicator to tell if you are living in a country that employs censorship as a means to control the population or not. Make no mistake, Governments are often ready to murder journalists to protect their public image, like in Mexico: [1] [2].
Essentially, the idea is to reduce your attack surface as much as possible, given the context of near-omnipresent surveillance, Privacy has it's limits, and Anonymity very often becomes the only way out of opression. If noone knows who did something, there can't be any repercussions for the perpetrating party.
In a way, Anonymity is superior to Privacy because whatever happened may have been hidden thanks to Privacy, but it may be discovered at a later point in time. Anonymity on the other hand, if maintained, remains a permanent way to act without any repercussions.
Until there is Nothing left.
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