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Merge pull request #3147 from uhoreg/cross_signing_backup_ssss

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Add information about using SSSS for cross-signing and key backup.
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Hubert Chathi 2021-04-27 19:09:30 -04:00 • committed by Richard van der Hoff
commit 194fef8022
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changelogs/client_server/newsfragments/3147.feature Normal file
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Add information about using SSSS for cross-signing and key backup.

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content/client-server-api/modules/end_to_end_encryption.md
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@ -944,6 +944,13 @@ example, if Alice and Bob verify each other using SAS, Alice's
`mac` property. Servers therefore must ensure that device IDs will not
collide with cross-signing public keys.
The cross-signing private keys can be stored on the server or shared with other
devices using the [Secrets](#secrets) module. When doing so, the master,
user-signing, and self-signing keys are identified using the names
`m.cross_signing.master`, `m.cross_signing.user_signing`, and
`m.cross_signing.self_signing`, respectively, and the keys are base64-encoded
before being encrypted.
###### Key and signature security
A user's master key could allow an attacker to impersonate that user to
@ -1083,6 +1090,11 @@ as follows:
When reading in a recovery key, clients must disregard whitespace, and
perform the reverse of steps 1 through 3.
The recovery key can also be stored on the server or shared with other devices
using the [Secrets](#secrets) module. When doing so, it is identified using the
name `m.megolm_backup.v1`, and the key is base64-encoded before being
encrypted.
###### Backup algorithm: `m.megolm_backup.v1.curve25519-aes-sha2`
When a backup is created with the `algorithm` set to