Moving SSRS reports from one Server to other
Just migrate the objects with the "ssrs_migration.rss" script.
Much easier than database keys and restores

rs.exe -i ssrs_migration.rss -e Mgmt2010 -s http://SourceServer/ReportServer -u Domain\User -p password -v ts="http://TargetServer/reportserver" -v tu="Domain\Userser" -v tp="password"


I've used this many times with good results

Script sources ("ssrs_migration.rss")


https://docs.microsoft.com/en-us/sql/reporting-services/tools/sample-reporting-services-rs-exe-script-to-copy-content-between-report-servers
https://msdn.microsoft.com/en-us/library/dn531017(v=sql.120).aspx