(Node.js) RSA-OAEP with SHA256 hashing

RSA encrypt a SHA256 hash with OAEP padding.

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

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    var pubkey = new chilkat.PublicKey();

    var sbPem = new chilkat.StringBuilder();
    var bCrlf = true;
    sbPem.AppendLine("-----BEGIN PUBLIC KEY-----",bCrlf);
    sbPem.AppendLine("MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA33TqqLR3eeUmDtHS89qF",bCrlf);
    sbPem.AppendLine("3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA",bCrlf);
    sbPem.AppendLine("04DDnEFGAf+kDQiNSe2ZtqC7bnIc8+KSG/qOGQIVaay4Ucr6ovDkykO5Hxn7OU7s",bCrlf);
    sbPem.AppendLine("Jp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwF",bCrlf);
    sbPem.AppendLine("wnxCsU5+UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUE",bCrlf);
    sbPem.AppendLine("f0YN3/Q0auBkdbDR/ES2PbgKTJdkjc/rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1W",bCrlf);
    sbPem.AppendLine("SwIDAQAB",bCrlf);
    sbPem.AppendLine("-----END PUBLIC KEY-----",bCrlf);

    // Load the public key object from the PEM. 
    var success = pubkey.LoadFromString(sbPem.GetAsString());
    if (success !== true) {
        console.log(pubkey.LastErrorText);
        return;
    }

    // Build a small string to encrypt
    var json = new chilkat.JsonObject();
    json.UpdateString("example","123");
    json.UpdateString("hello","world");
    console.log(json.Emit());

    // This is the JSON to be RSA encrypted:  {"example":"123","hello":"world"}

    // IMPORTANT: RSA encryption is only used to encrypt small amounts of data.
    // RSA is only able to encrypt data to a maximum amount of your key size (2048 bits = 256 bytes) 
    // minus padding / header data (11 bytes for PKCS#1 v1.5 padding, 42 bytes for OAEP).
    // As a result it is often not possible to encrypt files with RSA directly. 
    // RSA is also not meant for this purpose. 
    // 
    // If you want to encrypt more data, you can use something like:
    // 1) Generate a 256-bit random keystring K
    // 2) Encrypt your data with AES-CBC with K
    // 3) Encrypt K with RSA
    // 4) Send both to the other side 

    var rsa = new chilkat.Rsa();
    rsa.OaepPadding = true;
    rsa.OaepHash = "SHA-256";
    rsa.ImportPublicKeyObj(pubkey);
    rsa.EncodingMode = "base64";

    // Note: The OAEP padding uses random bytes in the padding, and therefore each time encryption happens,
    // even using the same data and key, the result will be different --  but still valid.  One should not expect
    // to get the same output.
    var bUsePrivateKey = false;
    var encryptedStr = rsa.EncryptStringENC(json.Emit(),bUsePrivateKey);
    if (rsa.LastMethodSuccess !== true) {
        console.log(rsa.LastErrorText);
        return;
    }

    console.log("Result: " + encryptedStr);

}

chilkatExample();