Signed Checksums for release archives

[Clint Armstrong]

The signed checksums at
https://www.freebsd.org/releases/10.2R/signatures.html provide a way to
verify installation sources, but there do not appear to be any signed
checksums for the release archives at
ftp://ftp.freebsd.org/pub/FreeBSD/releases/amd64/amd64/10.2-RELEASE/. Is
there another source of signed checksums hosted elsewhere or any other way
to verify archive downloads?