RsaSignatureStringFullNodeJs.js

const forge = require("node-forge");
var rsa = forge.pki.rsa;

console.log('RSA signature string');
const dataToSign = 'The quick brown fox jumps over the lazy dog';
console.log('dataToSign: ', dataToSign);

// usually we would load the private and public key from a file or keystore
// here we use hardcoded keys for demonstration - don't do this in real programs

console.log('\n* * * sign the plaintext with the RSA private key * * *');
var pki = forge.pki;
var privateKeyPem = getPrivateKeyPem();
var privateKey = pki.privateKeyFromPem(privateKeyPem);
console.log('used private key:\n', privateKeyPem);
const signatureBase64 = rsaSignToBase64(privateKey, dataToSign);
console.log('signature (Base64): ', signatureBase64);

console.log('\n* * * verify the signature against the plaintext with the RSA public key * * *');

var publicKeyPem = getPublicKeyPem();
var publicKey = pki.publicKeyFromPem(publicKeyPem);
console.log('used public_key:\n', publicKeyPem);
const signatureVerified = rsaVerifySignatureFromBase64(publicKey, dataToSign, signatureBase64);
console.log('\nsignature (Base64) verified: ', signatureVerified)

function rsaSignToBase64(privateKey, message) {
  var md256 = forge.md.sha256.create();
  md256.update(message, 'utf8');
  var signature = privateKey.sign(md256);
  return base64Encoding(signature);
}

function rsaVerifySignatureFromBase64(publicKey, message, signatureBase64) {
  var signature = base64Decoding(signatureBase64);
  var md256 = forge.md.sha256.create();
  md256.update(message, 'utf8');
  return publicKey.verify(md256.digest().bytes(), signature);
}

function getPrivateKeyPem() {
    const key = '-----BEGIN PRIVATE KEY-----\n' +
        'MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQDwSZYlRn86zPi9\n' +
        'e1RTZL7QzgE/36zjbeCMyOhf6o/WIKeVxFwVbG2FAY3YJZIxnBH+9j1XS6f+ewjG\n' +
        'FlJY4f2IrOpS1kPiO3fmOo5N4nc8JKvjwmKtUM0t63uFFPfs69+7mKJ4w3tk2mSN\n' +
        '4gb8J9P9BCXtH6Q78SdOYvdCMspA1X8eERsdLb/jjHs8+gepKqQ6+XwZbSq0vf2B\n' +
        'MtaAB7zTX/Dk+ZxDfwIobShPaB0mYmojE2YAQeRq1gYdwwO1dEGk6E5J2toWPpKY\n' +
        '/IcSYsGKyFqrsmbw0880r1BwRDer4RFrkzp4zvY+kX3eDanlyMqDLPN+ghXT1lv8\n' +
        'snZpbaBDAgMBAAECggEBAIVxmHzjBc11/73bPB2EGaSEg5UhdzZm0wncmZCLB453\n' +
        'XBqEjk8nhDsVfdzIIMSEVEowHijYz1c4pMq9osXR26eHwCp47AI73H5zjowadPVl\n' +
        'uEAot/xgn1IdMN/boURmSj44qiI/DcwYrTdOi2qGA+jD4PwrUl4nsxiJRZ/x7PjL\n' +
        'hMzRbvDxQ4/Q4ThYXwoEGiIBBK/iB3Z5eR7lFa8E5yAaxM2QP9PENBr/OqkGXLWV\n' +
        'qA/YTxs3gAvkUjMhlScOi7PMwRX9HsrAeLKbLuC1KJv1p2THUtZbOHqrAF/uwHaj\n' +
        'ygUblFaa/BTckTN7PKSVIhp7OihbD04bSRrh+nOilcECgYEA/8atV5DmNxFrxF1P\n' +
        'ODDjdJPNb9pzNrDF03TiFBZWS4Q+2JazyLGjZzhg5Vv9RJ7VcIjPAbMy2Cy5BUff\n' +
        'EFE+8ryKVWfdpPxpPYOwHCJSw4Bqqdj0Pmp/xw928ebrnUoCzdkUqYYpRWx0T7YV\n' +
        'RoA9RiBfQiVHhuJBSDPYJPoP34kCgYEA8H9wLE5L8raUn4NYYRuUVMa+1k4Q1N3X\n' +
        'Bixm5cccc/Ja4LVvrnWqmFOmfFgpVd8BcTGaPSsqfA4j/oEQp7tmjZqggVFqiM2m\n' +
        'J2YEv18cY/5kiDUVYR7VWSkpqVOkgiX3lK3UkIngnVMGGFnoIBlfBFF9uo02rZpC\n' +
        '5o5zebaDImsCgYAE9d5wv0+nq7/STBj4NwKCRUeLrsnjOqRriG3GA/TifAsX+jw8\n' +
        'XS2VF+PRLuqHhSkQiKazGr2Wsa9Y6d7qmxjEbmGkbGJBC+AioEYvFX9TaU8oQhvi\n' +
        'hgA6ZRNid58EKuZJBbe/3ek4/nR3A0oAVwZZMNGIH972P7cSZmb/uJXMOQKBgQCs\n' +
        'FaQAL+4sN/TUxrkAkylqF+QJmEZ26l2nrzHZjMWROYNJcsn8/XkaEhD4vGSnazCu\n' +
        '/B0vU6nMppmezF9Mhc112YSrw8QFK5GOc3NGNBoueqMYy1MG8Xcbm1aSMKVv8xba\n' +
        'rh+BZQbxy6x61CpCfaT9hAoA6HaNdeoU6y05lBz1DQKBgAbYiIk56QZHeoZKiZxy\n' +
        '4eicQS0sVKKRb24ZUd+04cNSTfeIuuXZrYJ48Jbr0fzjIM3EfHvLgh9rAZ+aHe/L\n' +
        '84Ig17KiExe+qyYHjut/SC0wODDtzM/jtrpqyYa5JoEpPIaUSgPuTH/WhO3cDsx6\n' +
        '3PIW4/CddNs8mCSBOqTnoaxh\n' +
        '-----END PRIVATE KEY-----\n'; // important last crlf
    return key;

}

function getPublicKeyPem() {
    const key = '-----BEGIN PUBLIC KEY-----\n' +
        'MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA8EmWJUZ/Osz4vXtUU2S+\n' +
        '0M4BP9+s423gjMjoX+qP1iCnlcRcFWxthQGN2CWSMZwR/vY9V0un/nsIxhZSWOH9\n' +
        'iKzqUtZD4jt35jqOTeJ3PCSr48JirVDNLet7hRT37Ovfu5iieMN7ZNpkjeIG/CfT\n' +
        '/QQl7R+kO/EnTmL3QjLKQNV/HhEbHS2/44x7PPoHqSqkOvl8GW0qtL39gTLWgAe8\n' +
        '01/w5PmcQ38CKG0oT2gdJmJqIxNmAEHkatYGHcMDtXRBpOhOSdraFj6SmPyHEmLB\n' +
        'ishaq7Jm8NPPNK9QcEQ3q+ERa5M6eM72PpF93g2p5cjKgyzzfoIV09Zb/LJ2aW2g\n' +
        'QwIDAQAB\n' +
        '-----END PUBLIC KEY-----\n'; // important last crlf
    return key;
}

function base64Encoding(input) {
  return forge.util.encode64(input);
}

function base64Decoding(input) {
  return forge.util.decode64(input);
}