Java Requires Chilkat v11.0.0+

RSA-OAEP with SHA256 hashing

See more RSA Examples

RSA encrypt a SHA256 hash with OAEP padding. Chilkat2 Java

import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.JsonObject;
import com.chilkatsoft.chilkat2.PublicKey;
import com.chilkatsoft.chilkat2.Rsa;
import com.chilkatsoft.chilkat2.StringBuilder;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example requires the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        PublicKey pubkey = new PublicKey();

        StringBuilder sbPem = new StringBuilder();
        boolean 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.
        try {
            pubkey.loadFromString(sbPem.getAsString());
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Build a small string to encrypt
        JsonObject json = new JsonObject();
        json.updateString("example", "123");
        json.updateString("hello", "world");
        System.out.println(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

        Rsa rsa = new Rsa();
        rsa.setPkcsPadding(false);
        rsa.setOaepHash("SHA-256");
        rsa.usePublicKey(pubkey);
        rsa.setEncodingMode("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.
        boolean bUsePrivateKey = false;
        String encryptedStr;
        try {
            encryptedStr = rsa.encryptStringENC(json.emit(), bUsePrivateKey);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Result: " + encryptedStr);
    }
}