RSA key convert to PEM file

How can I convert this RSA public key: 109120132967399429278860960508995541528237502902798129123468757937266291492576446330739696001110 6039072308886100726558188253585034290 57592827629436413108566029093628 21263595383668656267584开发者_开发问答97206207862794310902180176810615217550567108238764764442605581471797071 19674283982419152118103759076030616683978566631413

to *.pem file?

A "pem" file is not really a format, and different kinds of objects may be be stored in things called "pem" files. Most often these files contain either a base64-encoded X509 certificate or else a base64-encoded private key object.

Assuming you want an X509 certificate, you should next realize that a certificate consists of many fields, only one of which is the public key. So would need to decide on the values of the other fields. Finally, a certificate must be signed, with a private key.

PS. An RSA public key consists of a modulus and a public exponent. What is your public exponent?

If your hex string is just a simple convert from base64 to hex. Then you can reverse it. Here is the script I did (in PHP) to solve my case:

<?php

$list = array_slice($argv, 1);

foreach ($list as $file) {
    $hex = str_replace("\n", "", file_get_contents($file));
    $pem = str_replace(".hex", ".pem", $file);
    $b64 = base64_encode(hex2bin($hex));
    $fd = fopen($pem, 'w');
    fprintf($fd, "-----BEGIN PUBLIC KEY-----\n%s\n-----END PUBLIC KEY----\n", implode("\n", str_split($b64, 64)));
    fclose($fd);
}

Given a list of .hex files, it convert back to ".pem". You can run it like this:

php script.php *.hex

I would use OpenSSL. Assuming that you have the key in DER format, you can use this command to convert from DER to PEM.

openssl x509 -inform der -in input.der -out output.pem

If you are not sure whether you have the correctly formatted DER (ASN.1) encoded key, try this tool to parse your input file.

First of all President James K. Polk is right. A complete RSA Key is formed by a modulus and a public exponent. In Java, the interface RSAPublicKey from the package java.security.interfaces can hold well-formed RSA Keys. Assuming you have such object, the process of converting to a PEM format would involve encoding it, as follows:

String pemFormatKey = Base64.getEncoder().encodeToString(rsaPublicKey.getEncoded());

use putty programs, PuTTYgen does this conversion