Crypt::Perl::RSA::PrivateKey - object representation of an RSA
    private key
    #You’ll probably instantiate this class using Parser.pm
    #or Generate.pm.
    #cf. JSON Web Algorithms (RFC 7518, page 5)
    #These return an octet string.
    $sig = $prkey->sign_RS256($message);
    $sig = $prkey->sign_RS384($message);
    $sig = $prkey->sign_RS512($message);
    #These return 1 or 0 to indicate verification or non-verification.
    $prkey->verify_RS256($message, $sig);
    $prkey->verify_RS384($message, $sig);
    $prkey->verify_RS512($message, $sig);
    #----------------------------------------------------------------------
    my $enc = $prkey->encrypt_raw($payload);
    my $orig = $prkey->decrypt_raw($enc);
    #----------------------------------------------------------------------
    my $der = $prkey->to_der();
    my $pem = $prkey->to_pem();
    #For use in creating PKCS #10 CSRs and X.509 certificates
    my $pub_der = $prkey->to_subject_public_der();
    my $pbkey = $prkey->get_public_key();
    #----------------------------------------------------------------------
    $prkey->version();              #scalar, integer
    $prkey->size();                 #modulus length, in bits
    $prkey->modulus_byte_length();
    #----------------------------------------------------------------------
    # The following all return instances of Crypt::Perl::BigInt,
    # a subclass of Math::BigInt.
    # The pairs (e.g., modulus() and N()) are aliases.
    #----------------------------------------------------------------------
    $prkey->modulus();
    $prkey->N();
    $prkey->publicExponent();
    $prkey->E();
    $prkey->privateExponent();
    $prkey->D();
    $prkey->prime1();
    $prkey->P();
    $prkey->prime2();
    $prkey->Q();
    $prkey->exponent1();
    $prkey->DP();
    $prkey->exponent2();
    $prkey->DQ();
    $prkey->coefficient();
    $prkey->QINV();