(Node.js) Verify an RSA Signature Against the Signed String

See more Apple Keychain Examples

Demonstrates how to validate an RSA Signature against the string that was signed.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOS

var os = require('os');
if (os.platform() == 'win32') {  
  var chilkat = require('@chilkat/ck-node23-win64'); 
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node23-linux-arm');
    } else if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node23-linux-arm64');
    } else {
        var chilkat = require('@chilkat/ck-node23-linux-x64');
    }
} else if (os.platform() == 'darwin') {
  var chilkat = require('@chilkat/ck-node23-mac-universal');
}

function chilkatExample() {

    // Create the same string we previously signed in this example: 
    // RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

    var sb = new chilkat.StringBuilder();
    var crlfLineEnding = true;
    var i;
    for (i = 0; i <= 10; i++) {
        sb.AppendLine("This is a test.",crlfLineEnding);
    }

    var base64_rsa_sig = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ==";

    // Get the public key to be used for signature verification.
    var pubKey = new chilkat.PublicKey();
    var success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem");
    if (success == false) {
        console.log(pubKey.LastErrorText);
        return;
    }

    var rsa = new chilkat.Rsa();
    rsa.ImportPublicKeyObj(pubKey);

    // Verify the string against the signature.
    // We signed the utf-8 byte representation of the string, so we must indicate
    // to also validate against the utf-8 byte representation.
    rsa.Charset = "utf-8";
    rsa.EncodingMode = "base64";
    var signedString = sb.GetAsString();
    success = rsa.VerifyStringENC(signedString,"sha256",base64_rsa_sig);

    if (success == false) {
        console.log(rsa.LastErrorText);
        console.log("Signature invalid.");
    }
    else {
        console.log("Signature valid.");
    }


}

chilkatExample();