<p>Extract from the light novel - Volume 3 Fairy Dance (ALfheim arc), p67-68</p>

<blockquote>
  <p>With that in mind, I put the NERvGear on my head and buckled the
  chin strap. With the frame in place and the goggles down, I closed my
  eyes.</p>
  
  <p>Anxiety and excitement caused my heart to beat rapidly, as I tried to
  slow my racing heart beat, I said, “LINK START!”</p>
  
  <p>The light passing through my closed eyelids suddenly disappeared.
  The transmission from my optic nerves was suddenly severed, and my
  eyes were enveloped by darkness.</p>
  
  <p>[...]</p>
  
  <p>At last, the final OK appeared, and the next instant brought me falling
  through the darkness into the colors of a rainbow, an illusion of the
  world. After passing through this series of rings, I had arrived in a
  different world.</p>
  
  <p>-- Actually, it's still a little early to say that. Out of the darkness
  emerged an account registration interface. The main ALfheim Online
  LOGO gradually appeared, accompanied by a soft female voice.</p>
  
  <p>Following the instructions given, I began creating my account and
  character. At chest height was a pale and shiny virtual keyboard and I
  entered a User ID and password as prompted. I had many years of
  experience before beginning SAO, so this process was of some
  familiarity to me. Since this is a downloadable MMO game, I would
  normally need to select the payment method, but I had bought this
  game and it came with a one month free trial.</p>
  
  <p>Next I chose the nickname for my character. I didn’t put much thought
  into it, but entered the name «Kirito».</p>
</blockquote>

<p>The ALfheim Arc in the anime doesn't show all the details.</p>

<p>Since Kazuto used the same login in both games - as you may know, ALfheim's database is a clone of SAO's one - he kept the same account.</p>

CC BY-SA 3.0
2014-03-24T16:24:41.913Z
2015-01-11T09:31:04.423Z
2015-01-11T09:31:04.423Z
Hayenn
<p>Your question can pretty much be answered by watching episode 1 of <em>Sword Art Online</em>.</p>

<p>The Nerve Gear uses a username and password identification system as shown at 01:37 of episode 1.</p>

<p><img src="https://i.sstatic.net/MZapF.png" alt="Account and password login screen"></p>

<p>But as you mentioned, this does not occur in <em>Alfheim Online</em>. This is where we can consider the Nerve Gear to be the authentication factor, being a device that stores the save data.</p>

<blockquote class="spoiler">
  <p> We know it can save data Yui's data was saved to his Nerve Gear and was transferred to <em>Alfheim Online</em> as a result.</p>
</blockquote>

<hr>

<blockquote>
  <p>But if I steal your device, I could impersonate you in all games...</p>
</blockquote>

<p>This would indeed be true, but doesn't the same count for login credentials? If you steal somebody's username and password, you can also impersonate that person in game. And don't forget, it's harder to steal physical objects all around the world than to steal some username and password from your home computer.</p>

CC BY-SA 3.0
2015-02-23T14:30:10.673Z
Alfheim Online have a login system, but you cannot see it because isn't commented at novel or anime. You can know it because Asuna have two accounts (She reveals it at the end of Mother rosario arc).
Sakura Kinomoto
CC BY-SA 3.0
2014-03-23T19:49:31.147Z
2014-03-24T00:39:11.793Z
2014-03-24T00:39:11.793Z
Dimitri mx
<p>So there is a virtual reality device, the Nerve Gear, popularly used for MMOs.</p>

<p>As far as I'm concerned, we never see SAO or Alfheim using any sort of login screen.</p>

<p>Now, it makes sense for SAO to lack a login screen, since you can't log out. But what about Alfheim? How do normal, sane games authenticate their players?</p>

<ul>
<li>Do MMO Nerve Gear games use username/password credentials?
<ul>
<li>Is it implied <strong><em>anywhere</em></strong> in the series? If I recall correctly, Kirito would just put on his Nerve Gear and instantly enter Alfheim without any sort of password screen.</li>
</ul></li>
<li>Maybe the device serves as the credential itself?
<ul>
<li>But if I steal your device, I could impersonate you in all games...</li>
<li>Besides, using a device ID is not secure at all. If I figure out your device's ID, I could hack mine to use such ID and then login as yourself.</li>
</ul></li>
<li>Perhaps they do some complex biological scan on your body to create an unique ID...
<ul>
<li>That doesn't sound very reliable. Or healthy.</li>
</ul></li>
</ul>

CC BY-SA 3.0
2014-08-11T05:12:47.343Z
I don't know if I should comment or create a new question on this, but why would you need credentials if the gear is supposed to know who you are? Isn't the Nerve Gear almost equivalent to the best biometric interface ever? Yes, I realize there is a login and password in canon, but technology wise, after your body has been registered, wouldn't/shouldn't the Nerve Gear interface to the game recognize you when you hook up again?
SrJoven
CC BY-SA 3.0
2014-08-17T22:29:09.907Z
@SrJoven: The way software determines your identity, be it a by a login or some clever biological data, is called a credential. Also, the Nerve Gear is clearly flawed (the first version could kill people, and the second version can lower the pain limiters to the point it can cause physical damage), so we can't really assume it is as great as it seems.
Saturn
CC BY-SA 3.0
2014-08-17T22:31:40.370Z
@SrJoven: As for why using biometrics is flawed, consider being involved in some horrible accident: your biometrics could have been affected. Your general physical structure, your voice, or even your own mental status could have been modified. Now you can't login because your biometrics don't seem to match.
Saturn
CC BY-SA 3.0
2014-08-17T23:53:57.330Z
@Omega assuming all three: voice, mental status, physical structure have been altered, are you really you anymore? With the two factor identification, (who you are and what you know) it should be nearly impossible to login with someone else's creds. Nonetheless, SAO's mirror already knows what you look like. And ALO knows (knew) how you think, dream... This would be hard to spoof.
SrJoven
CC BY-SA 3.0
2014-08-18T00:54:22.560Z
@SrJoven: Hence it is still flawed - like any authentication system. The way you look, or the way you think, all of that can change. Whether it means if "you are still you" is too subjective - but essentially, the being is the same, so they should be allowed to enter the game. Otherwise who could? XD
Saturn
CC BY-SA 3.0
2014-08-18T11:32:56.817Z
@Omega This should have been moved to chat. I doubt that gear that knows your body mechanics well enough to use them in battle is so flawed that it can be spoofed or prevent login for the same person. But hey, I guess it would have to adapt to the new person who stole your login and password, because all the biometrics doesn't matter, even though that's an integral part of the game. You would have a hard time spoofing [voice](http://www.itnewsafrica.com/2014/01/voice-biometrics-solves-most-authentication-problems/) though certainly accommodations can be made for disabilities.
SrJoven
CC BY-SA 3.0
2014-08-18T20:54:04.187Z
@SrJoven exactly, that's why it is no better than using a simple login password.
Saturn
CC BY-SA 3.0
2014-03-23T11:35:37.677Z
Actually, I'm pretty sure there was a login screen, at the very beginning of the series, when he says "Link start!", you see a login screen and him inputting a username and a password.
Madara's Ghost
CC BY-SA 3.0
2014-03-23T12:10:04.793Z
Yep, there was an account/password in the first episode.
Deathspike
<sword-art-online>
How do online Nerve Gear games handle player authentication?
# How do online Nerve Gear games handle player authentication?
Posted by: username_0 on 2014-03-23
So there is a virtual reality device, the Nerve Gear, popularly used for MMOs.

As far as I'm concerned, we never see SAO or Alfheim using any sort of login screen.

Now, it makes sense for SAO to lack a login screen, since you can't log out. But what about Alfheim? How do normal, sane games authenticate their players?

* Do MMO Nerve Gear games use username/password credentials?
  + Is it implied ***anywhere*** in the series? If I recall correctly, Kirito would just put on his Nerve Gear and instantly enter Alfheim without any sort of password screen.
* Maybe the device serves as the credential itself?
  + But if I steal your device, I could impersonate you in all games...
  + Besides, using a device ID is not secure at all. If I figure out your device's ID, I could hack mine to use such ID and then login as yourself.
* Perhaps they do some complex biological scan on your body to create an unique ID...
  + That doesn't sound very reliable. Or healthy.
**Tags:** sword-art-online
> **Comments:**
> **username_2**: Actually, I'm pretty sure there was a login screen, at the very beginning of the series, when he says "Link start!", you see a login screen and him inputting a username and a password.  
> **username_3**: Yep, there was an account/password in the first episode.  
> **username_1**: I don't know if I should comment or create a new question on this, but why would you need credentials if the gear is supposed to know who you are? Isn't the Nerve Gear almost equivalent to the best biometric interface ever? Yes, I realize there is a login and password in canon, but technology wise, after your body has been registered, wouldn't/shouldn't the Nerve Gear interface to the game recognize you when you hook up again?  
> **username_0**: @SrJoven: The way software determines your identity, be it a by a login or some clever biological data, is called a credential. Also, the Nerve Gear is clearly flawed (the first version could kill people, and the second version can lower the pain limiters to the point it can cause physical damage), so we can't really assume it is as great as it seems.  
> **username_0**: @SrJoven: As for why using biometrics is flawed, consider being involved in some horrible accident: your biometrics could have been affected. Your general physical structure, your voice, or even your own mental status could have been modified. Now you can't login because your biometrics don't seem to match.  
> **username_1**: @Omega assuming all three: voice, mental status, physical structure have been altered, are you really you anymore? With the two factor identification, (who you are and what you know) it should be nearly impossible to login with someone else's creds. Nonetheless, SAO's mirror already knows what you look like. And ALO knows (knew) how you think, dream... This would be hard to spoof.  
> **username_0**: @SrJoven: Hence it is still flawed - like any authentication system. The way you look, or the way you think, all of that can change. Whether it means if "you are still you" is too subjective - but essentially, the being is the same, so they should be allowed to enter the game. Otherwise who could? XD  
> **username_1**: @Omega This should have been moved to chat. I doubt that gear that knows your body mechanics well enough to use them in battle is so flawed that it can be spoofed or prevent login for the same person. But hey, I guess it would have to adapt to the new person who stole your login and password, because all the biometrics doesn't matter, even though that's an integral part of the game. You would have a hard time spoofing [voice](http://www.itnewsafrica.com/2014/01/voice-biometrics-solves-most-authentication-problems/) though certainly accommodations can be made for disabilities.  
> **username_0**: @SrJoven exactly, that's why it is no better than using a simple login password.  
---
## 2 answers
### Answer by username_5 on 2014-03-23. Score: 16 | Accepted answer
Your question can pretty much be answered by watching episode 1 of *Sword Art Online*.

The Nerve Gear uses a username and password identification system as shown at 01:37 of episode 1.

![Account and password login screen](https://i.sstatic.net/MZapF.png)

But as you mentioned, this does not occur in *Alfheim Online*. This is where we can consider the Nerve Gear to be the authentication factor, being a device that stores the save data.

> We know it can save data Yui's data was saved to his Nerve Gear and was transferred to *Alfheim Online* as a result.

---

> But if I steal your device, I could impersonate you in all games...

This would indeed be true, but doesn't the same count for login credentials? If you steal somebody's username and password, you can also impersonate that person in game. And don't forget, it's harder to steal physical objects all around the world than to steal some username and password from your home computer.
> **Comments:**
> **username_6** (2015-02-23): Alfheim Online have a login system, but you cannot see it because isn't commented at novel or anime. You can know it because Asuna have two accounts (She reveals it at the end of Mother rosario arc).  
---
### Answer by username_4 on 2014-03-24. Score: 9
Extract from the light novel - Volume 3 Fairy Dance (ALfheim arc), p67-68

> With that in mind, I put the NERvGear on my head and buckled the
> chin strap. With the frame in place and the goggles down, I closed my
> eyes.
>
> Anxiety and excitement caused my heart to beat rapidly, as I tried to
> slow my racing heart beat, I said, “LINK START!”
>
> The light passing through my closed eyelids suddenly disappeared.
> The transmission from my optic nerves was suddenly severed, and my
> eyes were enveloped by darkness.
>
> [...]
>
> At last, the final OK appeared, and the next instant brought me falling
> through the darkness into the colors of a rainbow, an illusion of the
> world. After passing through this series of rings, I had arrived in a
> different world.
>
> -- Actually, it's still a little early to say that. Out of the darkness
> emerged an account registration interface. The main ALfheim Online
> LOGO gradually appeared, accompanied by a soft female voice.
>
> Following the instructions given, I began creating my account and
> character. At chest height was a pale and shiny virtual keyboard and I
> entered a User ID and password as prompted. I had many years of
> experience before beginning SAO, so this process was of some
> familiarity to me. Since this is a downloadable MMO game, I would
> normally need to select the payment method, but I had bought this
> game and it came with a one month free trial.
>
> Next I chose the nickname for my character. I didn’t put much thought
> into it, but entered the name «Kirito».

The ALfheim Arc in the anime doesn't show all the details.

Since Kazuto used the same login in both games - as you may know, ALfheim's database is a clone of SAO's one - he kept the same account.
---
