Networks and addresses
RPKI and ROAs
Signed statements of which AS number may announce which IP prefix, so routers can drop hijacked or mistyped BGP announcements.
RPKI is a public-key infrastructure run by the regional registries. The holder of an IP block creates a Route Origin Authorisation, a ROA, saying "AS 199839 may originate 31.24.249.0/24 with a maximum length of /24". The ROA is signed with keys that chain back to the registry that allocated the block.
Routers fetch the validated ROAs and compare BGP announcements against them. An announcement from a different AS, or for a longer prefix than the ROA allows, is "invalid", and most large networks now drop invalids. That stops the classic hijack, where a network announces someone else's prefix by mistake or on purpose, from spreading.
If you hold address space and announce it, create ROAs for every prefix and AS you use, and nothing else. A missing ROA leaves you "unknown", which is still accepted; a wrong ROA makes your own announcement invalid. End users with sponsored PI space create their ROAs through the sponsoring LIR.