matrix-spec-proposals/proposals/3122-deprecate-starting-ver...

# MSC3122: Deprecate starting key verifications without requesting first

Currently, the spec allows a device to begin a verification via to-device
messages by sending an `m.key.verification.start` event without first sending
or receiving an `m.key.verification.request` message.  However, doing so does
not provide a good user experience, and allowing this adds unnecessary
complexity to implementations.

We propose to deprecate allowing this behaviour.

Note that verifications in DMs do not allow this behaviour.  Currently, Element
Web is the only client known to do this.

## Proposal

The ability to begin a key verification by sending an
`m.key.verification.start` event as a to-device event without a prior
`m.key.verification.request` is deprecated.  New clients should not begin
verifications in this way, but will still need to accept verifications begun in
this way, until it is removed from the spec.

## Potential issues

None.

## Alternatives

We could do nothing and leave it in the spec.  But we should clean up cruft when
possible.

## Security considerations

None.

## Unstable prefix

No unstable prefix is removed since we are simply deprecating behaviour.
I should pay attention when my editor says that things are misspelled 3 years ago			`# MSC3122: Deprecate starting key verifications without requesting first`
deprecate starting verifications without first requesting 3 years ago
			`Currently, the spec allows a device to begin a verification via to-device`
			messages by sending an `m.key.verification.start` event without first sending
			or receiving an `m.key.verification.request` message. However, doing so does
			`not provide a good user experience, and allowing this adds unnecessary`
			`complexity to implementations.`

			`We propose to deprecate allowing this behaviour.`

			`Note that verifications in DMs do not allow this behaviour. Currently, Element`
			`Web is the only client known to do this.`

			`## Proposal`

			`The ability to begin a key verification by sending an`
			`m.key.verification.start` event as a to-device event without a prior
			`m.key.verification.request` is deprecated. New clients should not begin
			`verifications in this way, but will still need to accept verifications begun in`
			`this way, until it is removed from the spec.`

			`## Potential issues`

			`None.`

			`## Alternatives`

			`We could do nothing and leave it in the spec. But we should clean up cruft when`
			`possible.`

			`## Security considerations`

			`None.`

			`## Unstable prefix`

			`No unstable prefix is removed since we are simply deprecating behaviour.`