Define hkdf-hmac-sha256.v2 MAC method for SAS verification #1412
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richvdh
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Feb 7, 2023
data/event-schemas/schema/m.key.verification.start$m.sas.v1.yaml
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richvdh
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Feb 7, 2023
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| * the keys that they wish to verify (usually their device ed25519 key and | ||
| their master cross-signing key) | ||
| * the list of key IDs that they wish the other user to verify. |
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So as I understand it, Alice and Bob will each calculate 3 MACs:
- their device Ed25519 key
- their master cross-signing key
- the string consisting of
<ed25519 key id>,<MSK key id>.
Is that correct? Is the key list just to stop people doing a switcheroo on which keys are being verified?
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Yes, the key list is to prevent people from adding or removing keys
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| If the key list is being MACed, the list is sorted lexicographically and | ||
| comma-separated with no extra whitespace added, with each key written in the | ||
| form `{algorithm}:{keyId}`. For example, the key list could look like: | ||
| `ed25519:Cross+Signing+Key,ed25519:DEVICEID`. In this way, the recipient can | ||
| reconstruct the list from the names in the `mac` property of the | ||
| `m.key.verification.mac` message and ensure that no keys were added or removed. |
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we still don't seem to say how to feed a key into the MAC.
Do we use the 43(?) bytes of Base64-encoded public key? Or the 32 bytes of binary public key? Or other?
Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
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clokep
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…g#1412) Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
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Spec PR for matrix-org/matrix-spec-proposals#3783
Changes are in https://pr1412--matrix-spec-previews.netlify.app/client-server-api/#short-authentication-string-sas-verification
Preview: https://pr1412--matrix-spec-previews.netlify.app