Caveats apply......
http://www.theregister.co.uk/2017/05/19/wannacrypt_key_recovery_tool/
they link to the tool here-
https://github.com/aguinet/wannakey
http://www.theregister.co.uk/2017/05/19/wannacrypt_key_recovery_tool/
they link to the tool here-
https://github.com/aguinet/wannakey