The returned Hash from these methods contain 0 in place of a missing parameter in the key, for example: pkey = OpenSSL::PKey.read(OpenSSL::PKey::RSA.new(2048).public_to_pem) pp pkey.params #=> # {"n"=>#<OpenSSL::BN https://github.com/ruby/openssl/commit/286934673421[...snip]>, # "e"=>#<OpenSSL::BN 65537>, # "d"=>#<OpenSSL::BN 0>, # "p"=>#<OpenSSL::BN 0>, # "q"=>#<OpenSSL::BN 0>, # "dmp1"=>#<OpenSSL::BN 0>, # "dmq1"=>#<OpenSSL::BN 0>, # "iqmp"=>#<OpenSSL::BN 0>} Let's use nil instead, which is more appropriate for indicating a missing value. https://github.com/ruby/openssl/commit/f247ec3dec