aria2-1.18.8 has been released. Please, update portage.
aria2-1.18.9 was released on on 2015-02-01.
+*aria2-1.18.9 (21 Feb 2015) + + 21 Feb 2015; Michał Górny <mgorny@gentoo.org> +aria2-1.18.9.ebuild: + Version bump. Bugfixes, adler32 checksum support via --checksum and Metalink + files, SSLv3 disabled by default and --min-tls-version to select minimal + SSL/TLS version. --bt-force-encryption to require full BitTorrent encryption. Sorry for the awful delay.