How can I convert RSA PlblicKey XML to PEM format

Question

I receive a RSA Key from C# server through httprequest,

But so many Encrypt lib need PEM format.

I find a solution at this

XML to PEM in Node.js

But I can't use it in my Javscript H5 Project, Have any other solution?

Answer 1

Your XML seems a propietary format

<RSAKeyValue> 
    <Modulus>1znidPBIcMcO7K/53tkTSyKqxlG5Mcws8kVtijS4tyEU4W/FEVWYpOtv+Stnb4Vt</Modulus>
    <Exponent>AQAB</Exponent>
</RSAKeyValue>

You will need a cryptographic library like forge to build a RSA public key from modulus and exponent. Based on this thread , you can use a code similar to this

// parse XML
var rsaKeyValue = ...

var BigInteger = forge.jsbn.BigInteger;
function parseBigInteger(b64) {
     return new BigInteger(forge.util.createBuffer(forge.util.decode64(b64)).toHex(), 16);
 }

 //Create a Forge public key from modulus and exponent
 var publicKey = forge.pki.setRsaPublicKey(
       parseBigInteger(rsaKeyValue.Modulus), // n
       parseBigInteger(rsaKeyValue.Exponent)); // e

 // convert a Forge public key to PEM-format
 var pem = forge.pki.publicKeyToPem(publicKey);