Recently, the kernel.org servers were cracked by attackers who were able to gain root-level access. The attackers then inserted trojan horses into the source releases for certain Linux kernel release candidates (-rc releases). This attack caused a lot of work for the kernel. org system administrators and resulted in a number of discussion threads on the linux-kernel mailing list, considering ways to avoid similar security compromises in the future.

In one thread, Junio C Hamano, the Git maintainer, asked the kernel folks if there were any special Git features they wanted, that might increase the security of a Git archive that involved many contributors (e.g., the Linux kernel). He suggested providing the ability to cryptographically sign all pushes, as well as having Git produce more output on certain types of failure modes. Linus Torvalds replied, saying he liked the idea of increased verbosity; but, about cryptographic signatures, he said:

"I realize that cryptographic signatures sound very important right now, but in the end, *real* trust comes from people, not from signatures. Realistically, I checked a few signatures this time around due to the kernel.org issues, but at the same time, the thing that made me trust most of it was just looking at commits and the email messages. The unconscious and non-cryptographic 'signature' of a person acting like you expect a person to act."

"Technical measures can be subverted, and I think we should also think about the social side. Every time somebody mentions a signature,I want to also mention 'human readability', because I think that matters as much, if not more."