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--- services:matrix:encryption [2020/12/04 15:55] – behrmj87
+++ services:matrix:encryption [2021/08/10 14:39] – [The somewhat short story] behrmj87
@@ Line 2: / Line 2: @@
 ===== End-to-End-encryption for Matrix on Element=====
-<note important>End-to-End-encryption is currently enabled by default for direct chats. This has technical reasons.</note>
 End-to-end encryption means that only the parties participating in a conversation are able to decrypt and read the messages that were send. Our server is not able to decrypt the messages that were sent, preventing third parties to read the messages.
@@ Line 10: / Line 8: @@
 <note warning>When logging into a new device (a different browser, a new phone, your fridge), you will only get access to your already encrypted messages //after// verifying the new session. This is explained below (and most easily done if you use Element on your phone).</note>
-==== Upgrading encryption ====
-This step is necessary if you have used encryption in the past on your matrix.physik.fu-berlin.de account. If you have not used encryption previously, you can jump to the section [[services:matrix:start#setting_up_encryption_for_the_first_time | Setting up encryption for the first time ]]
+==== The somewhat short story ====
+Some chats you encounter will be encrypted. Direct conversations are encrypted by default and encryption for rooms for multiple people can be switched on. When using encryption in a room (or direct chat) all messages in that chat will be encrypted. Each of your clients (e.g. the web client at meet.physik.fu-berlin.de or Element on your phone) will have a session with its own keys. This is mostly transparent to you as a user, but you must always hold either of the following to be true to keep access to your old encrypted messages:
+    * Have one running session (in a browser on your computer, on your phone, wherever), so that new sessions can authenticate against the running session (cross-signing, described below), or
+    * have access to your recovery passphrase (that you should create when you first log in) to recover your encryption keys when you log into a new session and have no other running sessions to authenticate against.
-If you have used encryption before you will notice a small popup on the left side of the screen, asking you to upgrade. Click on the "upgrade" button to start the upgrade. {{ :services:matrix:riot_e2e_upgrade_01.png?direct&800 |}} Next you will have to enter your ZEDAT-password… {{./riot-e2e-doku-pictures/riot_e2e_upgrade_02.png |}} and enter your recovery passphrase you set when you set up key backups for encryption. If you can not remember your passphrase you can use the recovery key if you have still saved it somewhere. Alternatively you can set up a new key recovery. Your previous encrypted messages will still be available if you are able to read them on the device you are using to perform the upgrade. {{./riot-e2e-doku-pictures/riot_e2e_upgrade_03.png |}}
+This means, that if you do have encrypted messages, e.g. in a direct chat, and you were only logged into one session, e.g. only in the web client, and you don't have a Security Phrase or Security Key set up, i.e. you log out and decline to set one up, when asked, you will lose access to those messages.
-This concludes the upgrade. You can now on read how to verify users in //*Verify a user//, or use encrypted chats without verification.
+This may sound difficult, but it's not. Read on for what you need to do.
 ==== Setting up encryption for the first time ====
@@ Line 31: / Line 33: @@
 {{ :services:matrix:riot_e2e_setup_03.png |}}
+==== Verifying a session ====
-==== Verification ====
+To access your messages from encrypted chats, e.g. direct conversations, it is necessary to verify a new session. To verify a session you can either confirm a new session from an existing session, which is the easiest way, or enter your recovery passphrase.
-**This step is optional** **If you choose to not verify a user there will be a black shield displayed next to their user icon** {{ :services:matrix:riot_e2e_verification_icon_1.png |}}
+When logging in with a new device you will get prompted to verify it.
-For end-to-end encryption to be really secure users have to verify they are talking to each other. To do this each user is verifying each their devices, and additionally verifies every user once. Every device another verified user verified themselves will be considered verified.
+{{ :services:matrix:verifylogin.png |}}
-A user you did not verify will be displayed with a black shield next to their user icon: {{ :services:matrix:riot_e2e_verification_icon_1.png |}}
+The three options:
+- **Use another login**, which will authenticate against a running session, e.g. on a phone or another computer.
+- **Use Security Key or Phrase**, which works without another session, i.e. without another device, but you will need the Security Phrase or Key that you set up earlier.
+- **Skip**, which skips authentication, but you won't be able to read encrypted messages that were sent to you earlier.
-A user you verified, but who did not verify all of their devices will be displayed with a red shield next to their user icon: {{ :services:matrix:riot_e2e_verification_icon_3.png |}}
+=== Verifying a Sessin using a Security Phrase ===
-A user you verified and who verified all of their devices will be displayed with a red shield next to their user icon: {{ :services:matrix:riot_e2e_verification_icon_2.png |}}
+This is conceptually the easiest so, we'll discuss it first. Click **Use Security Key or Phrase** and in the screen that opens enter either your *Security Phrase* or your *Security Key*.
-Example: Alice and Bob start a conversation in their logged in sessions. For the encryption to be secure they have to verify they are actually talking to each other. In Element this is done by comparing a list of emojis that are shown to both users. Alice requests a verification with Bob and they verify they get shown the same string of emojis. When Bob starts using a new session (e.g. using a different Browser/Device) he can use the session that was verified with Alice's session to also verify his new session. Alice's session automatically sees that Bob verified the new session and accepts it into the encrypted conversation.
+{{ :services:matrix:securitypassphrase.png |}}
-==== Verify a user ====
+If you enter either correctly, you will be greeted by this happy screen
-For this step to make sense you have to be able to communicate with the other user in a way that makes sure you are actually talking to ****them****. For this we recommend video/audio-chat, or just sitting next to each other.
+{{ :services:matrix:sessionverified.png |}}
-To verify a user you open a chat you share with the user and click their name in the user side bar.
+=== Verifying a Sessin using a Security Phrase ===
-{{ :services:matrix:riot_e2e_verify_user_01.png?direct&800 |}}
+If you are logged into another session, e.g. on your phone, it's easiest to click **Use another login**. There are multiple ways how this is handled, which depends on where the other session is running, e.g. Element on phones will allow you to do this via scanning a QR code. All methods do require, though, that you have the device where the other session is running on *at hand* otherwise the whole process will block waiting for you to do something on the other device, which is hard to do, if it's far away.
-Click on the verify link in the sidebar…
+One method that is always available is comparing emoji shown on both devices. First you will be asked on the device with an already authenticated session whether the new session is you and whether you want to authenticate it.
-{{ :services:matrix:riot_e2e_verify_user_02.png?direct&800 |}}
-and click on the "Start Verification" button.
-{{ :services:matrix:riot_e2e_verify_user_03.png?direct&800 |}}
-The user you want to verify will see the request as a popup on the left and in the chat.
-{{ :services:matrix:riot_e2e_verify_user_04.png |}} {{./riot-e2e-doku-pictures/riot_e2e_verify_user_05.png |}}
-You will then be presented with the verification options. Currently the only option is comparing a string of emojis. When both users have agreed on a verification method the verification process begins.
-If the user you are verifying with is shown the same string of emojis as you are, you can both click on "They match" to complete the verification.
-{{ :services:matrix:riot_e2e_verify_user_08.png |}}
-==== Verify a session ====
-To access your encryption history and for other users to verify you it is necessary to verify a new session. To verify a session you can either confirm a new session from an existing session or enter your recovery passphrase.
-When logging in with a new device you will get prompted to verify it.
-{{ :services:matrix:riot_e2e_verify_session_01.png?direct&800 |}}
-If you are logged into another session there will be a popup asking you to verify the new session:
 {{ :services:matrix:riot_e2e_verify_session_02.png?direct&800 |}}
@@ Line 88: / Line 68: @@
 {{ :services:matrix:riot_e2e_verify_session_03.png |}}
-Select to continue and you will be asked for a verification method. Currently the only option is to compare a sting of emojis.
+Select to continue and you will be asked for a verification method.
 {{ :services:matrix:riot_e2e_verify_session_04.png |}}
@@ Line 98: / Line 78: @@
 {{ :services:matrix:riot_e2e_verify_session_06.png |}}
-Confirm the emojis match on both devices to complete verifying the session.
+Confirm the emojis match on both devices to complete verifying the session and you get the happy result of a verified session.
-Alternatively you can select to verify a session by using your recovery passphrase:
+{{ :services:matrix:sessionverified.png |}}
-{{ :services:matrix:riot_e2e_verify_session_09.png?direct&800 |}}
 ==== Deleting a session ====
@@ Line 133: / Line 112: @@
+==== Verifying a user ====
+**This step is optional** **If you choose to not verify a user there will be a black shield displayed next to their user icon** {{ :services:matrix:riot_e2e_verification_icon_1.png |}}
+For end-to-end encryption to be really secure users have to verify they are talking to each other. To do this each user is verifying each their devices, and additionally verifies every user once. Every device another verified user verified themselves will be considered verified.
+A user you did not verify will be displayed with a black shield next to their user icon: {{ :services:matrix:riot_e2e_verification_icon_1.png |}}
+A user you verified, but who did not verify all of their devices will be displayed with a red shield next to their user icon: {{ :services:matrix:riot_e2e_verification_icon_3.png |}}
+A user you verified and who verified all of their devices will be displayed with a red shield next to their user icon: {{ :services:matrix:riot_e2e_verification_icon_2.png |}}
+Example: Alice and Bob start a conversation in their logged in sessions. For the encryption to be secure they have to verify they are actually talking to each other. In Element this is done by comparing a list of emojis that are shown to both users. Alice requests a verification with Bob and they verify they get shown the same string of emojis. When Bob starts using a new session (e.g. using a different Browser/Device) he can use the session that was verified with Alice's session to also verify his new session. Alice's session automatically sees that Bob verified the new session and accepts it into the encrypted conversation.
+For this step to make sense you have to be able to communicate with the other user in a way that makes sure you are actually talking to ****them****. For this we recommend video/audio-chat, or just sitting next to each other.
+To verify a user you open a chat you share with the user and click their name in the user side bar.
+{{ :services:matrix:riot_e2e_verify_user_01.png?direct&800 |}}
+Click on the verify link in the sidebar…
+{{ :services:matrix:riot_e2e_verify_user_02.png?direct&800 |}}
+and click on the "Start Verification" button.
+{{ :services:matrix:riot_e2e_verify_user_03.png?direct&800 |}}
+The user you want to verify will see the request as a popup on the left and in the chat.
+{{ :services:matrix:riot_e2e_verify_user_04.png |}} {{./riot-e2e-doku-pictures/riot_e2e_verify_user_05.png |}}
+You will then be presented with the verification options. Currently the only option is comparing a string of emojis. When both users have agreed on a verification method the verification process begins.
+If the user you are verifying with is shown the same string of emojis as you are, you can both click on "They match" to complete the verification.
+{{ :services:matrix:riot_e2e_verify_user_08.png |}}
+==== I've lost all my keys! What now? ====
+Sometimes it happens. Your computer and phone die at the same time and those were the only clients you were logged in at and you didn't save your passwordmanager database (hopefully you are using one) where you store your recovery keys or recovery passphrase to any other device. What now?
+Well, all your encrypted messages, i.e. messages in rooms or private discussions were encryption was enabled, are gone and you won't get them back, but you can make yourself new recovery keys for the future (and hopefully you will safe them redundantly). To this, just click **Use Security Key or Phrase**
+{{ :services:matrix:verifylogin.png |}}
+on the verification dialog after login and instead of entering your security phrase or key, which you've lost, click the **Reset all** link on the bottom, next to *Forgotten or lost all recovery methods?*
+You will then be asked to confirm
+{{ :services:matrix:reseteverything.png |}}
+And clicking **Reset** will sign out of all your old sessions and delete all keys, followed by guiding you through the procedure to generate new ones described above.