Not much to say about signatures, other than: every signature is coupled with an accurate
*theoretically, though always possible to spoof into the past if no other signatures contradict it.
timestamp of the time the signature was applied. The other point to keep in mind about signatures is that multiple types of signatures are possible
*at this time: ECDSA 256 and RSA 3072 are supported
and that new public-private signature types may be added in the future. Also, for chains which implement share expiration, old signature types may be phased out; for instance ECDSA 256 is not thought to be particularly robust against quantum attack, so it may be deprecated at some point in the future and no new signatures accepted using that technology.