(JavaScript) RSA-OAEP with SHA256 hashing

RSA encrypt a SHA256 hash with OAEP padding.

Note: This example requires Chilkat v11.0.0 or greater.

Note

This example is intended for running within a Chilkat.Js embedded JavaScript engine. All Chilkat JavaScript examples require Chilkat v11.4.0 or greater.

var success = false;

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

var pubkey = new CkPublicKey();

var sbPem = new CkStringBuilder();
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. 
success = pubkey.LoadFromString(sbPem.GetAsString());
if (success == false) {
    console.log(pubkey.LastErrorText);
    return;
}

// Build a small string to encrypt
var json = new CkJsonObject();
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 CkRsa();
rsa.PkcsPadding = false;
rsa.OaepHash = "SHA-256";
rsa.UsePublicKey(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 == false) {
    console.log(rsa.LastErrorText);
    return;
}

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