require 'openssl'
#
#if ARGV.length < 2 || ARGV[2] != 'yes-i-know-that-burning-a-rotpk-might-brick-my-device'
#   puts 'Usage: mkrotpk public-key.pem rotpk.bin do-you-know-what-you-are-doing?'
#   exit false
#end
#
key = OpenSSL::PKey::RSA.new(File.read(ARGV[0]))
#
n = key.params['n']
e = key.params['e']

if n.num_bits != 2048
    puts 'Need 2048-bit RSA key'
    exit false
end

n = [n.to_s(16)].pack('H*')
e = [e.to_s(16)].pack('H*')
#
if n.length != 256
    puts 'fatal: n.length != 256 bytes'
    exit false
end
#
if e.length > 256
    puts 'fatal: e.length > 256 bytes'
    exit false
end
#
data = n + e.ljust(256, "\x91".b)
rotpk = OpenSSL::Digest::SHA256.digest(data)
#
File.binwrite(ARGV[1], rotpk)
#
#