"Later, Gavin Andrsen (through reddit) gave details of this verification process for CW
Craig signed a message that I chose (“Gavin’s favorite number is eleven. CSW” if I recall correctly) using the private key from block number 1.
That signature was copied on to a clean usb stick I brought with me to London, and then validated on a brand-new laptop with a freshly downloaded copy of electrum.
I was not allowed to keep the message or laptop (fear it would leak before Official Announcement).
I don’t have an explanation for the funky OpenSSL procedure in his blog post".
https://medium.com/@BlockByBlock/will-the-real-satoshi-please-stand-up-c97a670c4055