The y-value listed in the file:
"y":"IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4",
is not valid base64! "-" is not a base64 character according to https://en.wikipedia.org/wiki/Base64 and RFC4648. My ruby decoding does not automatically process it. Your encoding is base64url encoded.
Base64.urlsafe_decode64(str) solves this problem, but I wonder if the examples should be coded
into stock base64?