There is a typo in the "kerneli.org" address, which should be "kernel.org" in option "Cryptographic API > Serpent cipher algorithm" of the kernel configuration.
Quote from the option description:
"Keys are allowed to be from 0 to 256 bits in length, in steps
of 8 bits. Also includes the 'Tnepres' algorithm, a reversed
variant of Serpent for compatibility with old kerneli.org code."
"kerneli.org" here is correct, not a typo.