const id         = '__JUNK__';
// Public key need to be in PKCS8 format
// ssh-keygen -e -m PKCS8 -f id_rsa.pub > id_rsa.pkcs8
const publicKey  = fs.readFileSync(path.join(__dirname, 'id_rsa.pkcs8'), { encoding : 'utf8' });
const privateKey = fs.readFileSync(path.join(__dirname, 'id_rsa'), { encoding : 'utf8' });

// Sign
const signer = crypto.createSign('RSA-SHA512');
signer.update(id);
const signature = signer.sign(privateKey, 'hex');

// ...

// Verify
const verifier = crypto.createVerify('RSA-SHA512');
verifier.update(ruid);
const publicKeyBuf = new Buffer(publicKey, 'utf-8');
const signatureBuf = new Buffer(signature, 'hex');
const result       = verifier.verify(publicKeyBuf, signatureBuf);