torbrowser signature verification fails – a glitch or an “attack”?

I wanted to try using TOR on my new Linux Mint 18.1 installation. So I apt-get installed torbrowser-launcher and tor, then ran torbrowser-launcher. It opened a dialog box and showed me it was downloading the TOR browser; but when it was done, it said it had failed the signature check and that I may be “under attack” (oh my!).

Add TCP congestion control variant to Linux Ubuntu

I want to test different variants of TCP in Linux Ubuntu. I have Ubuntu 14.04 LTS with Kernel version 3.14. When I check the available congestion control algorithm using the following command sysctl net.ipv4.tcp_available_congestion_control I get only: cubic and reno. However, I want to test other variants like Hybla, HighSpeed. If I run the menuconfig I can select the variants which I want and compile the Kernel. But in my case, I already have the kernel compiled so is it possible to have some Linux package which contains TCP variants as loadable kernel modules?