[Full Changelog](https://github.com/matrix-org/matrix-js-sdk/compare/v5.1.1...v5.2.0-rc.1) * Add a flag for whether cross signing signatures are trusted [\#1285](https://github.com/matrix-org/matrix-js-sdk/pull/1285) * Cache user and self signing keys during bootstrap [\#1282](https://github.com/matrix-org/matrix-js-sdk/pull/1282) * remove unnecessary promise [\#1283](https://github.com/matrix-org/matrix-js-sdk/pull/1283) * Functions to cache session backups key automatically [\#1281](https://github.com/matrix-org/matrix-js-sdk/pull/1281) * Add function for checking cross-signing is ready [\#1279](https://github.com/matrix-org/matrix-js-sdk/pull/1279) * Use symmetric encryption for SSSS [\#1228](https://github.com/matrix-org/matrix-js-sdk/pull/1228) * Migrate SSSS to use symmetric algorithm [\#1238](https://github.com/matrix-org/matrix-js-sdk/pull/1238) * Migration to symmetric SSSS [\#1272](https://github.com/matrix-org/matrix-js-sdk/pull/1272) * Reduce number of one-time-key requests [\#1280](https://github.com/matrix-org/matrix-js-sdk/pull/1280) * Fix: assume the requested method is supported by other party with to_device [\#1275](https://github.com/matrix-org/matrix-js-sdk/pull/1275) * Use checkDeviceTrust when computing untrusted devices [\#1278](https://github.com/matrix-org/matrix-js-sdk/pull/1278) * Add a store for backup keys [\#1271](https://github.com/matrix-org/matrix-js-sdk/pull/1271) * Upload only new device signature of master key [\#1268](https://github.com/matrix-org/matrix-js-sdk/pull/1268) * Expose prepareToEncrypt in the client API [\#1270](https://github.com/matrix-org/matrix-js-sdk/pull/1270) * Don't kill the whole device download if one device gives an error [\#1269](https://github.com/matrix-org/matrix-js-sdk/pull/1269) * Handle racing .start event during self verification [\#1267](https://github.com/matrix-org/matrix-js-sdk/pull/1267) * A crypto.keySignatureUploadFailure event reported the wrong source [\#1266](https://github.com/matrix-org/matrix-js-sdk/pull/1266) * Fix editing of unsent messages by waiting for actual event id [\#1263](https://github.com/matrix-org/matrix-js-sdk/pull/1263) * Fix: ensureOlmSessionsForDevices parameter format [\#1264](https://github.com/matrix-org/matrix-js-sdk/pull/1264) * Remove stuff that yarn install doesn't think we need [\#1261](https://github.com/matrix-org/matrix-js-sdk/pull/1261) * Fix: prevent error being thrown during sync in some cases [\#1258](https://github.com/matrix-org/matrix-js-sdk/pull/1258) * Force `is_verified` for key backups to bool and fix computation [\#1259](https://github.com/matrix-org/matrix-js-sdk/pull/1259) * Add a method for legacy single device verification, returning a verification request [\#1257](https://github.com/matrix-org/matrix-js-sdk/pull/1257) * yarn upgrade [\#1256](https://github.com/matrix-org/matrix-js-sdk/pull/1256)